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|
1 |
+
from sympy.calculus.accumulationbounds import AccumBounds
|
2 |
+
from sympy.core.function import (expand_mul, expand_trig)
|
3 |
+
from sympy.core.numbers import (E, I, Integer, Rational, nan, oo, pi, zoo)
|
4 |
+
from sympy.core.singleton import S
|
5 |
+
from sympy.core.symbol import (Symbol, symbols)
|
6 |
+
from sympy.functions.elementary.complexes import (im, re)
|
7 |
+
from sympy.functions.elementary.exponential import (exp, log)
|
8 |
+
from sympy.functions.elementary.hyperbolic import (acosh, acoth, acsch, asech, asinh, atanh, cosh, coth, csch, sech, sinh, tanh)
|
9 |
+
from sympy.functions.elementary.miscellaneous import sqrt
|
10 |
+
from sympy.functions.elementary.trigonometric import (acos, asin, cos, cot, sec, sin, tan)
|
11 |
+
from sympy.series.order import O
|
12 |
+
|
13 |
+
from sympy.core.expr import unchanged
|
14 |
+
from sympy.core.function import ArgumentIndexError
|
15 |
+
from sympy.testing.pytest import raises
|
16 |
+
|
17 |
+
|
18 |
+
def test_sinh():
|
19 |
+
x, y = symbols('x,y')
|
20 |
+
|
21 |
+
k = Symbol('k', integer=True)
|
22 |
+
|
23 |
+
assert sinh(nan) is nan
|
24 |
+
assert sinh(zoo) is nan
|
25 |
+
|
26 |
+
assert sinh(oo) is oo
|
27 |
+
assert sinh(-oo) is -oo
|
28 |
+
|
29 |
+
assert sinh(0) == 0
|
30 |
+
|
31 |
+
assert unchanged(sinh, 1)
|
32 |
+
assert sinh(-1) == -sinh(1)
|
33 |
+
|
34 |
+
assert unchanged(sinh, x)
|
35 |
+
assert sinh(-x) == -sinh(x)
|
36 |
+
|
37 |
+
assert unchanged(sinh, pi)
|
38 |
+
assert sinh(-pi) == -sinh(pi)
|
39 |
+
|
40 |
+
assert unchanged(sinh, 2**1024 * E)
|
41 |
+
assert sinh(-2**1024 * E) == -sinh(2**1024 * E)
|
42 |
+
|
43 |
+
assert sinh(pi*I) == 0
|
44 |
+
assert sinh(-pi*I) == 0
|
45 |
+
assert sinh(2*pi*I) == 0
|
46 |
+
assert sinh(-2*pi*I) == 0
|
47 |
+
assert sinh(-3*10**73*pi*I) == 0
|
48 |
+
assert sinh(7*10**103*pi*I) == 0
|
49 |
+
|
50 |
+
assert sinh(pi*I/2) == I
|
51 |
+
assert sinh(-pi*I/2) == -I
|
52 |
+
assert sinh(pi*I*Rational(5, 2)) == I
|
53 |
+
assert sinh(pi*I*Rational(7, 2)) == -I
|
54 |
+
|
55 |
+
assert sinh(pi*I/3) == S.Half*sqrt(3)*I
|
56 |
+
assert sinh(pi*I*Rational(-2, 3)) == Rational(-1, 2)*sqrt(3)*I
|
57 |
+
|
58 |
+
assert sinh(pi*I/4) == S.Half*sqrt(2)*I
|
59 |
+
assert sinh(-pi*I/4) == Rational(-1, 2)*sqrt(2)*I
|
60 |
+
assert sinh(pi*I*Rational(17, 4)) == S.Half*sqrt(2)*I
|
61 |
+
assert sinh(pi*I*Rational(-3, 4)) == Rational(-1, 2)*sqrt(2)*I
|
62 |
+
|
63 |
+
assert sinh(pi*I/6) == S.Half*I
|
64 |
+
assert sinh(-pi*I/6) == Rational(-1, 2)*I
|
65 |
+
assert sinh(pi*I*Rational(7, 6)) == Rational(-1, 2)*I
|
66 |
+
assert sinh(pi*I*Rational(-5, 6)) == Rational(-1, 2)*I
|
67 |
+
|
68 |
+
assert sinh(pi*I/105) == sin(pi/105)*I
|
69 |
+
assert sinh(-pi*I/105) == -sin(pi/105)*I
|
70 |
+
|
71 |
+
assert unchanged(sinh, 2 + 3*I)
|
72 |
+
|
73 |
+
assert sinh(x*I) == sin(x)*I
|
74 |
+
|
75 |
+
assert sinh(k*pi*I) == 0
|
76 |
+
assert sinh(17*k*pi*I) == 0
|
77 |
+
|
78 |
+
assert sinh(k*pi*I/2) == sin(k*pi/2)*I
|
79 |
+
|
80 |
+
assert sinh(x).as_real_imag(deep=False) == (cos(im(x))*sinh(re(x)),
|
81 |
+
sin(im(x))*cosh(re(x)))
|
82 |
+
x = Symbol('x', extended_real=True)
|
83 |
+
assert sinh(x).as_real_imag(deep=False) == (sinh(x), 0)
|
84 |
+
|
85 |
+
x = Symbol('x', real=True)
|
86 |
+
assert sinh(I*x).is_finite is True
|
87 |
+
assert sinh(x).is_real is True
|
88 |
+
assert sinh(I).is_real is False
|
89 |
+
p = Symbol('p', positive=True)
|
90 |
+
assert sinh(p).is_zero is False
|
91 |
+
assert sinh(0, evaluate=False).is_zero is True
|
92 |
+
assert sinh(2*pi*I, evaluate=False).is_zero is True
|
93 |
+
|
94 |
+
|
95 |
+
def test_sinh_series():
|
96 |
+
x = Symbol('x')
|
97 |
+
assert sinh(x).series(x, 0, 10) == \
|
98 |
+
x + x**3/6 + x**5/120 + x**7/5040 + x**9/362880 + O(x**10)
|
99 |
+
|
100 |
+
|
101 |
+
def test_sinh_fdiff():
|
102 |
+
x = Symbol('x')
|
103 |
+
raises(ArgumentIndexError, lambda: sinh(x).fdiff(2))
|
104 |
+
|
105 |
+
|
106 |
+
def test_cosh():
|
107 |
+
x, y = symbols('x,y')
|
108 |
+
|
109 |
+
k = Symbol('k', integer=True)
|
110 |
+
|
111 |
+
assert cosh(nan) is nan
|
112 |
+
assert cosh(zoo) is nan
|
113 |
+
|
114 |
+
assert cosh(oo) is oo
|
115 |
+
assert cosh(-oo) is oo
|
116 |
+
|
117 |
+
assert cosh(0) == 1
|
118 |
+
|
119 |
+
assert unchanged(cosh, 1)
|
120 |
+
assert cosh(-1) == cosh(1)
|
121 |
+
|
122 |
+
assert unchanged(cosh, x)
|
123 |
+
assert cosh(-x) == cosh(x)
|
124 |
+
|
125 |
+
assert cosh(pi*I) == cos(pi)
|
126 |
+
assert cosh(-pi*I) == cos(pi)
|
127 |
+
|
128 |
+
assert unchanged(cosh, 2**1024 * E)
|
129 |
+
assert cosh(-2**1024 * E) == cosh(2**1024 * E)
|
130 |
+
|
131 |
+
assert cosh(pi*I/2) == 0
|
132 |
+
assert cosh(-pi*I/2) == 0
|
133 |
+
assert cosh((-3*10**73 + 1)*pi*I/2) == 0
|
134 |
+
assert cosh((7*10**103 + 1)*pi*I/2) == 0
|
135 |
+
|
136 |
+
assert cosh(pi*I) == -1
|
137 |
+
assert cosh(-pi*I) == -1
|
138 |
+
assert cosh(5*pi*I) == -1
|
139 |
+
assert cosh(8*pi*I) == 1
|
140 |
+
|
141 |
+
assert cosh(pi*I/3) == S.Half
|
142 |
+
assert cosh(pi*I*Rational(-2, 3)) == Rational(-1, 2)
|
143 |
+
|
144 |
+
assert cosh(pi*I/4) == S.Half*sqrt(2)
|
145 |
+
assert cosh(-pi*I/4) == S.Half*sqrt(2)
|
146 |
+
assert cosh(pi*I*Rational(11, 4)) == Rational(-1, 2)*sqrt(2)
|
147 |
+
assert cosh(pi*I*Rational(-3, 4)) == Rational(-1, 2)*sqrt(2)
|
148 |
+
|
149 |
+
assert cosh(pi*I/6) == S.Half*sqrt(3)
|
150 |
+
assert cosh(-pi*I/6) == S.Half*sqrt(3)
|
151 |
+
assert cosh(pi*I*Rational(7, 6)) == Rational(-1, 2)*sqrt(3)
|
152 |
+
assert cosh(pi*I*Rational(-5, 6)) == Rational(-1, 2)*sqrt(3)
|
153 |
+
|
154 |
+
assert cosh(pi*I/105) == cos(pi/105)
|
155 |
+
assert cosh(-pi*I/105) == cos(pi/105)
|
156 |
+
|
157 |
+
assert unchanged(cosh, 2 + 3*I)
|
158 |
+
|
159 |
+
assert cosh(x*I) == cos(x)
|
160 |
+
|
161 |
+
assert cosh(k*pi*I) == cos(k*pi)
|
162 |
+
assert cosh(17*k*pi*I) == cos(17*k*pi)
|
163 |
+
|
164 |
+
assert unchanged(cosh, k*pi)
|
165 |
+
|
166 |
+
assert cosh(x).as_real_imag(deep=False) == (cos(im(x))*cosh(re(x)),
|
167 |
+
sin(im(x))*sinh(re(x)))
|
168 |
+
x = Symbol('x', extended_real=True)
|
169 |
+
assert cosh(x).as_real_imag(deep=False) == (cosh(x), 0)
|
170 |
+
|
171 |
+
x = Symbol('x', real=True)
|
172 |
+
assert cosh(I*x).is_finite is True
|
173 |
+
assert cosh(I*x).is_real is True
|
174 |
+
assert cosh(I*2 + 1).is_real is False
|
175 |
+
assert cosh(5*I*S.Pi/2, evaluate=False).is_zero is True
|
176 |
+
assert cosh(x).is_zero is False
|
177 |
+
|
178 |
+
|
179 |
+
def test_cosh_series():
|
180 |
+
x = Symbol('x')
|
181 |
+
assert cosh(x).series(x, 0, 10) == \
|
182 |
+
1 + x**2/2 + x**4/24 + x**6/720 + x**8/40320 + O(x**10)
|
183 |
+
|
184 |
+
|
185 |
+
def test_cosh_fdiff():
|
186 |
+
x = Symbol('x')
|
187 |
+
raises(ArgumentIndexError, lambda: cosh(x).fdiff(2))
|
188 |
+
|
189 |
+
|
190 |
+
def test_tanh():
|
191 |
+
x, y = symbols('x,y')
|
192 |
+
|
193 |
+
k = Symbol('k', integer=True)
|
194 |
+
|
195 |
+
assert tanh(nan) is nan
|
196 |
+
assert tanh(zoo) is nan
|
197 |
+
|
198 |
+
assert tanh(oo) == 1
|
199 |
+
assert tanh(-oo) == -1
|
200 |
+
|
201 |
+
assert tanh(0) == 0
|
202 |
+
|
203 |
+
assert unchanged(tanh, 1)
|
204 |
+
assert tanh(-1) == -tanh(1)
|
205 |
+
|
206 |
+
assert unchanged(tanh, x)
|
207 |
+
assert tanh(-x) == -tanh(x)
|
208 |
+
|
209 |
+
assert unchanged(tanh, pi)
|
210 |
+
assert tanh(-pi) == -tanh(pi)
|
211 |
+
|
212 |
+
assert unchanged(tanh, 2**1024 * E)
|
213 |
+
assert tanh(-2**1024 * E) == -tanh(2**1024 * E)
|
214 |
+
|
215 |
+
assert tanh(pi*I) == 0
|
216 |
+
assert tanh(-pi*I) == 0
|
217 |
+
assert tanh(2*pi*I) == 0
|
218 |
+
assert tanh(-2*pi*I) == 0
|
219 |
+
assert tanh(-3*10**73*pi*I) == 0
|
220 |
+
assert tanh(7*10**103*pi*I) == 0
|
221 |
+
|
222 |
+
assert tanh(pi*I/2) is zoo
|
223 |
+
assert tanh(-pi*I/2) is zoo
|
224 |
+
assert tanh(pi*I*Rational(5, 2)) is zoo
|
225 |
+
assert tanh(pi*I*Rational(7, 2)) is zoo
|
226 |
+
|
227 |
+
assert tanh(pi*I/3) == sqrt(3)*I
|
228 |
+
assert tanh(pi*I*Rational(-2, 3)) == sqrt(3)*I
|
229 |
+
|
230 |
+
assert tanh(pi*I/4) == I
|
231 |
+
assert tanh(-pi*I/4) == -I
|
232 |
+
assert tanh(pi*I*Rational(17, 4)) == I
|
233 |
+
assert tanh(pi*I*Rational(-3, 4)) == I
|
234 |
+
|
235 |
+
assert tanh(pi*I/6) == I/sqrt(3)
|
236 |
+
assert tanh(-pi*I/6) == -I/sqrt(3)
|
237 |
+
assert tanh(pi*I*Rational(7, 6)) == I/sqrt(3)
|
238 |
+
assert tanh(pi*I*Rational(-5, 6)) == I/sqrt(3)
|
239 |
+
|
240 |
+
assert tanh(pi*I/105) == tan(pi/105)*I
|
241 |
+
assert tanh(-pi*I/105) == -tan(pi/105)*I
|
242 |
+
|
243 |
+
assert unchanged(tanh, 2 + 3*I)
|
244 |
+
|
245 |
+
assert tanh(x*I) == tan(x)*I
|
246 |
+
|
247 |
+
assert tanh(k*pi*I) == 0
|
248 |
+
assert tanh(17*k*pi*I) == 0
|
249 |
+
|
250 |
+
assert tanh(k*pi*I/2) == tan(k*pi/2)*I
|
251 |
+
|
252 |
+
assert tanh(x).as_real_imag(deep=False) == (sinh(re(x))*cosh(re(x))/(cos(im(x))**2
|
253 |
+
+ sinh(re(x))**2),
|
254 |
+
sin(im(x))*cos(im(x))/(cos(im(x))**2 + sinh(re(x))**2))
|
255 |
+
x = Symbol('x', extended_real=True)
|
256 |
+
assert tanh(x).as_real_imag(deep=False) == (tanh(x), 0)
|
257 |
+
assert tanh(I*pi/3 + 1).is_real is False
|
258 |
+
assert tanh(x).is_real is True
|
259 |
+
assert tanh(I*pi*x/2).is_real is None
|
260 |
+
|
261 |
+
|
262 |
+
def test_tanh_series():
|
263 |
+
x = Symbol('x')
|
264 |
+
assert tanh(x).series(x, 0, 10) == \
|
265 |
+
x - x**3/3 + 2*x**5/15 - 17*x**7/315 + 62*x**9/2835 + O(x**10)
|
266 |
+
|
267 |
+
|
268 |
+
def test_tanh_fdiff():
|
269 |
+
x = Symbol('x')
|
270 |
+
raises(ArgumentIndexError, lambda: tanh(x).fdiff(2))
|
271 |
+
|
272 |
+
|
273 |
+
def test_coth():
|
274 |
+
x, y = symbols('x,y')
|
275 |
+
|
276 |
+
k = Symbol('k', integer=True)
|
277 |
+
|
278 |
+
assert coth(nan) is nan
|
279 |
+
assert coth(zoo) is nan
|
280 |
+
|
281 |
+
assert coth(oo) == 1
|
282 |
+
assert coth(-oo) == -1
|
283 |
+
|
284 |
+
assert coth(0) is zoo
|
285 |
+
assert unchanged(coth, 1)
|
286 |
+
assert coth(-1) == -coth(1)
|
287 |
+
|
288 |
+
assert unchanged(coth, x)
|
289 |
+
assert coth(-x) == -coth(x)
|
290 |
+
|
291 |
+
assert coth(pi*I) == -I*cot(pi)
|
292 |
+
assert coth(-pi*I) == cot(pi)*I
|
293 |
+
|
294 |
+
assert unchanged(coth, 2**1024 * E)
|
295 |
+
assert coth(-2**1024 * E) == -coth(2**1024 * E)
|
296 |
+
|
297 |
+
assert coth(pi*I) == -I*cot(pi)
|
298 |
+
assert coth(-pi*I) == I*cot(pi)
|
299 |
+
assert coth(2*pi*I) == -I*cot(2*pi)
|
300 |
+
assert coth(-2*pi*I) == I*cot(2*pi)
|
301 |
+
assert coth(-3*10**73*pi*I) == I*cot(3*10**73*pi)
|
302 |
+
assert coth(7*10**103*pi*I) == -I*cot(7*10**103*pi)
|
303 |
+
|
304 |
+
assert coth(pi*I/2) == 0
|
305 |
+
assert coth(-pi*I/2) == 0
|
306 |
+
assert coth(pi*I*Rational(5, 2)) == 0
|
307 |
+
assert coth(pi*I*Rational(7, 2)) == 0
|
308 |
+
|
309 |
+
assert coth(pi*I/3) == -I/sqrt(3)
|
310 |
+
assert coth(pi*I*Rational(-2, 3)) == -I/sqrt(3)
|
311 |
+
|
312 |
+
assert coth(pi*I/4) == -I
|
313 |
+
assert coth(-pi*I/4) == I
|
314 |
+
assert coth(pi*I*Rational(17, 4)) == -I
|
315 |
+
assert coth(pi*I*Rational(-3, 4)) == -I
|
316 |
+
|
317 |
+
assert coth(pi*I/6) == -sqrt(3)*I
|
318 |
+
assert coth(-pi*I/6) == sqrt(3)*I
|
319 |
+
assert coth(pi*I*Rational(7, 6)) == -sqrt(3)*I
|
320 |
+
assert coth(pi*I*Rational(-5, 6)) == -sqrt(3)*I
|
321 |
+
|
322 |
+
assert coth(pi*I/105) == -cot(pi/105)*I
|
323 |
+
assert coth(-pi*I/105) == cot(pi/105)*I
|
324 |
+
|
325 |
+
assert unchanged(coth, 2 + 3*I)
|
326 |
+
|
327 |
+
assert coth(x*I) == -cot(x)*I
|
328 |
+
|
329 |
+
assert coth(k*pi*I) == -cot(k*pi)*I
|
330 |
+
assert coth(17*k*pi*I) == -cot(17*k*pi)*I
|
331 |
+
|
332 |
+
assert coth(k*pi*I) == -cot(k*pi)*I
|
333 |
+
|
334 |
+
assert coth(log(tan(2))) == coth(log(-tan(2)))
|
335 |
+
assert coth(1 + I*pi/2) == tanh(1)
|
336 |
+
|
337 |
+
assert coth(x).as_real_imag(deep=False) == (sinh(re(x))*cosh(re(x))/(sin(im(x))**2
|
338 |
+
+ sinh(re(x))**2),
|
339 |
+
-sin(im(x))*cos(im(x))/(sin(im(x))**2 + sinh(re(x))**2))
|
340 |
+
x = Symbol('x', extended_real=True)
|
341 |
+
assert coth(x).as_real_imag(deep=False) == (coth(x), 0)
|
342 |
+
|
343 |
+
assert expand_trig(coth(2*x)) == (coth(x)**2 + 1)/(2*coth(x))
|
344 |
+
assert expand_trig(coth(3*x)) == (coth(x)**3 + 3*coth(x))/(1 + 3*coth(x)**2)
|
345 |
+
|
346 |
+
assert expand_trig(coth(x + y)) == (1 + coth(x)*coth(y))/(coth(x) + coth(y))
|
347 |
+
|
348 |
+
|
349 |
+
def test_coth_series():
|
350 |
+
x = Symbol('x')
|
351 |
+
assert coth(x).series(x, 0, 8) == \
|
352 |
+
1/x + x/3 - x**3/45 + 2*x**5/945 - x**7/4725 + O(x**8)
|
353 |
+
|
354 |
+
|
355 |
+
def test_coth_fdiff():
|
356 |
+
x = Symbol('x')
|
357 |
+
raises(ArgumentIndexError, lambda: coth(x).fdiff(2))
|
358 |
+
|
359 |
+
|
360 |
+
def test_csch():
|
361 |
+
x, y = symbols('x,y')
|
362 |
+
|
363 |
+
k = Symbol('k', integer=True)
|
364 |
+
n = Symbol('n', positive=True)
|
365 |
+
|
366 |
+
assert csch(nan) is nan
|
367 |
+
assert csch(zoo) is nan
|
368 |
+
|
369 |
+
assert csch(oo) == 0
|
370 |
+
assert csch(-oo) == 0
|
371 |
+
|
372 |
+
assert csch(0) is zoo
|
373 |
+
|
374 |
+
assert csch(-1) == -csch(1)
|
375 |
+
|
376 |
+
assert csch(-x) == -csch(x)
|
377 |
+
assert csch(-pi) == -csch(pi)
|
378 |
+
assert csch(-2**1024 * E) == -csch(2**1024 * E)
|
379 |
+
|
380 |
+
assert csch(pi*I) is zoo
|
381 |
+
assert csch(-pi*I) is zoo
|
382 |
+
assert csch(2*pi*I) is zoo
|
383 |
+
assert csch(-2*pi*I) is zoo
|
384 |
+
assert csch(-3*10**73*pi*I) is zoo
|
385 |
+
assert csch(7*10**103*pi*I) is zoo
|
386 |
+
|
387 |
+
assert csch(pi*I/2) == -I
|
388 |
+
assert csch(-pi*I/2) == I
|
389 |
+
assert csch(pi*I*Rational(5, 2)) == -I
|
390 |
+
assert csch(pi*I*Rational(7, 2)) == I
|
391 |
+
|
392 |
+
assert csch(pi*I/3) == -2/sqrt(3)*I
|
393 |
+
assert csch(pi*I*Rational(-2, 3)) == 2/sqrt(3)*I
|
394 |
+
|
395 |
+
assert csch(pi*I/4) == -sqrt(2)*I
|
396 |
+
assert csch(-pi*I/4) == sqrt(2)*I
|
397 |
+
assert csch(pi*I*Rational(7, 4)) == sqrt(2)*I
|
398 |
+
assert csch(pi*I*Rational(-3, 4)) == sqrt(2)*I
|
399 |
+
|
400 |
+
assert csch(pi*I/6) == -2*I
|
401 |
+
assert csch(-pi*I/6) == 2*I
|
402 |
+
assert csch(pi*I*Rational(7, 6)) == 2*I
|
403 |
+
assert csch(pi*I*Rational(-7, 6)) == -2*I
|
404 |
+
assert csch(pi*I*Rational(-5, 6)) == 2*I
|
405 |
+
|
406 |
+
assert csch(pi*I/105) == -1/sin(pi/105)*I
|
407 |
+
assert csch(-pi*I/105) == 1/sin(pi/105)*I
|
408 |
+
|
409 |
+
assert csch(x*I) == -1/sin(x)*I
|
410 |
+
|
411 |
+
assert csch(k*pi*I) is zoo
|
412 |
+
assert csch(17*k*pi*I) is zoo
|
413 |
+
|
414 |
+
assert csch(k*pi*I/2) == -1/sin(k*pi/2)*I
|
415 |
+
|
416 |
+
assert csch(n).is_real is True
|
417 |
+
|
418 |
+
assert expand_trig(csch(x + y)) == 1/(sinh(x)*cosh(y) + cosh(x)*sinh(y))
|
419 |
+
|
420 |
+
|
421 |
+
def test_csch_series():
|
422 |
+
x = Symbol('x')
|
423 |
+
assert csch(x).series(x, 0, 10) == \
|
424 |
+
1/ x - x/6 + 7*x**3/360 - 31*x**5/15120 + 127*x**7/604800 \
|
425 |
+
- 73*x**9/3421440 + O(x**10)
|
426 |
+
|
427 |
+
|
428 |
+
def test_csch_fdiff():
|
429 |
+
x = Symbol('x')
|
430 |
+
raises(ArgumentIndexError, lambda: csch(x).fdiff(2))
|
431 |
+
|
432 |
+
|
433 |
+
def test_sech():
|
434 |
+
x, y = symbols('x, y')
|
435 |
+
|
436 |
+
k = Symbol('k', integer=True)
|
437 |
+
n = Symbol('n', positive=True)
|
438 |
+
|
439 |
+
assert sech(nan) is nan
|
440 |
+
assert sech(zoo) is nan
|
441 |
+
|
442 |
+
assert sech(oo) == 0
|
443 |
+
assert sech(-oo) == 0
|
444 |
+
|
445 |
+
assert sech(0) == 1
|
446 |
+
|
447 |
+
assert sech(-1) == sech(1)
|
448 |
+
assert sech(-x) == sech(x)
|
449 |
+
|
450 |
+
assert sech(pi*I) == sec(pi)
|
451 |
+
|
452 |
+
assert sech(-pi*I) == sec(pi)
|
453 |
+
assert sech(-2**1024 * E) == sech(2**1024 * E)
|
454 |
+
|
455 |
+
assert sech(pi*I/2) is zoo
|
456 |
+
assert sech(-pi*I/2) is zoo
|
457 |
+
assert sech((-3*10**73 + 1)*pi*I/2) is zoo
|
458 |
+
assert sech((7*10**103 + 1)*pi*I/2) is zoo
|
459 |
+
|
460 |
+
assert sech(pi*I) == -1
|
461 |
+
assert sech(-pi*I) == -1
|
462 |
+
assert sech(5*pi*I) == -1
|
463 |
+
assert sech(8*pi*I) == 1
|
464 |
+
|
465 |
+
assert sech(pi*I/3) == 2
|
466 |
+
assert sech(pi*I*Rational(-2, 3)) == -2
|
467 |
+
|
468 |
+
assert sech(pi*I/4) == sqrt(2)
|
469 |
+
assert sech(-pi*I/4) == sqrt(2)
|
470 |
+
assert sech(pi*I*Rational(5, 4)) == -sqrt(2)
|
471 |
+
assert sech(pi*I*Rational(-5, 4)) == -sqrt(2)
|
472 |
+
|
473 |
+
assert sech(pi*I/6) == 2/sqrt(3)
|
474 |
+
assert sech(-pi*I/6) == 2/sqrt(3)
|
475 |
+
assert sech(pi*I*Rational(7, 6)) == -2/sqrt(3)
|
476 |
+
assert sech(pi*I*Rational(-5, 6)) == -2/sqrt(3)
|
477 |
+
|
478 |
+
assert sech(pi*I/105) == 1/cos(pi/105)
|
479 |
+
assert sech(-pi*I/105) == 1/cos(pi/105)
|
480 |
+
|
481 |
+
assert sech(x*I) == 1/cos(x)
|
482 |
+
|
483 |
+
assert sech(k*pi*I) == 1/cos(k*pi)
|
484 |
+
assert sech(17*k*pi*I) == 1/cos(17*k*pi)
|
485 |
+
|
486 |
+
assert sech(n).is_real is True
|
487 |
+
|
488 |
+
assert expand_trig(sech(x + y)) == 1/(cosh(x)*cosh(y) + sinh(x)*sinh(y))
|
489 |
+
|
490 |
+
|
491 |
+
def test_sech_series():
|
492 |
+
x = Symbol('x')
|
493 |
+
assert sech(x).series(x, 0, 10) == \
|
494 |
+
1 - x**2/2 + 5*x**4/24 - 61*x**6/720 + 277*x**8/8064 + O(x**10)
|
495 |
+
|
496 |
+
|
497 |
+
def test_sech_fdiff():
|
498 |
+
x = Symbol('x')
|
499 |
+
raises(ArgumentIndexError, lambda: sech(x).fdiff(2))
|
500 |
+
|
501 |
+
|
502 |
+
def test_asinh():
|
503 |
+
x, y = symbols('x,y')
|
504 |
+
assert unchanged(asinh, x)
|
505 |
+
assert asinh(-x) == -asinh(x)
|
506 |
+
|
507 |
+
#at specific points
|
508 |
+
assert asinh(nan) is nan
|
509 |
+
assert asinh( 0) == 0
|
510 |
+
assert asinh(+1) == log(sqrt(2) + 1)
|
511 |
+
|
512 |
+
assert asinh(-1) == log(sqrt(2) - 1)
|
513 |
+
assert asinh(I) == pi*I/2
|
514 |
+
assert asinh(-I) == -pi*I/2
|
515 |
+
assert asinh(I/2) == pi*I/6
|
516 |
+
assert asinh(-I/2) == -pi*I/6
|
517 |
+
|
518 |
+
# at infinites
|
519 |
+
assert asinh(oo) is oo
|
520 |
+
assert asinh(-oo) is -oo
|
521 |
+
|
522 |
+
assert asinh(I*oo) is oo
|
523 |
+
assert asinh(-I *oo) is -oo
|
524 |
+
|
525 |
+
assert asinh(zoo) is zoo
|
526 |
+
|
527 |
+
#properties
|
528 |
+
assert asinh(I *(sqrt(3) - 1)/(2**Rational(3, 2))) == pi*I/12
|
529 |
+
assert asinh(-I *(sqrt(3) - 1)/(2**Rational(3, 2))) == -pi*I/12
|
530 |
+
|
531 |
+
assert asinh(I*(sqrt(5) - 1)/4) == pi*I/10
|
532 |
+
assert asinh(-I*(sqrt(5) - 1)/4) == -pi*I/10
|
533 |
+
|
534 |
+
assert asinh(I*(sqrt(5) + 1)/4) == pi*I*Rational(3, 10)
|
535 |
+
assert asinh(-I*(sqrt(5) + 1)/4) == pi*I*Rational(-3, 10)
|
536 |
+
|
537 |
+
# Symmetry
|
538 |
+
assert asinh(Rational(-1, 2)) == -asinh(S.Half)
|
539 |
+
|
540 |
+
# inverse composition
|
541 |
+
assert unchanged(asinh, sinh(Symbol('v1')))
|
542 |
+
|
543 |
+
assert asinh(sinh(0, evaluate=False)) == 0
|
544 |
+
assert asinh(sinh(-3, evaluate=False)) == -3
|
545 |
+
assert asinh(sinh(2, evaluate=False)) == 2
|
546 |
+
assert asinh(sinh(I, evaluate=False)) == I
|
547 |
+
assert asinh(sinh(-I, evaluate=False)) == -I
|
548 |
+
assert asinh(sinh(5*I, evaluate=False)) == -2*I*pi + 5*I
|
549 |
+
assert asinh(sinh(15 + 11*I)) == 15 - 4*I*pi + 11*I
|
550 |
+
assert asinh(sinh(-73 + 97*I)) == 73 - 97*I + 31*I*pi
|
551 |
+
assert asinh(sinh(-7 - 23*I)) == 7 - 7*I*pi + 23*I
|
552 |
+
assert asinh(sinh(13 - 3*I)) == -13 - I*pi + 3*I
|
553 |
+
p = Symbol('p', positive=True)
|
554 |
+
assert asinh(p).is_zero is False
|
555 |
+
assert asinh(sinh(0, evaluate=False), evaluate=False).is_zero is True
|
556 |
+
|
557 |
+
|
558 |
+
def test_asinh_rewrite():
|
559 |
+
x = Symbol('x')
|
560 |
+
assert asinh(x).rewrite(log) == log(x + sqrt(x**2 + 1))
|
561 |
+
assert asinh(x).rewrite(atanh) == atanh(x/sqrt(1 + x**2))
|
562 |
+
assert asinh(x).rewrite(asin) == asinh(x)
|
563 |
+
assert asinh(x*(1 + I)).rewrite(asin) == -I*asin(I*x*(1+I))
|
564 |
+
assert asinh(x).rewrite(acos) == I*(-I*asinh(x) + pi/2) - I*pi/2
|
565 |
+
|
566 |
+
|
567 |
+
def test_asinh_leading_term():
|
568 |
+
x = Symbol('x')
|
569 |
+
assert asinh(x).as_leading_term(x, cdir=1) == x
|
570 |
+
# Tests concerning branch points
|
571 |
+
assert asinh(x + I).as_leading_term(x, cdir=1) == I*pi/2
|
572 |
+
assert asinh(x - I).as_leading_term(x, cdir=1) == -I*pi/2
|
573 |
+
assert asinh(1/x).as_leading_term(x, cdir=1) == -log(x) + log(2)
|
574 |
+
assert asinh(1/x).as_leading_term(x, cdir=-1) == log(x) - log(2) - I*pi
|
575 |
+
# Tests concerning points lying on branch cuts
|
576 |
+
assert asinh(x + 2*I).as_leading_term(x, cdir=1) == I*asin(2)
|
577 |
+
assert asinh(x + 2*I).as_leading_term(x, cdir=-1) == -I*asin(2) + I*pi
|
578 |
+
assert asinh(x - 2*I).as_leading_term(x, cdir=1) == -I*pi + I*asin(2)
|
579 |
+
assert asinh(x - 2*I).as_leading_term(x, cdir=-1) == -I*asin(2)
|
580 |
+
# Tests concerning re(ndir) == 0
|
581 |
+
assert asinh(2*I + I*x - x**2).as_leading_term(x, cdir=1) == log(2 - sqrt(3)) + I*pi/2
|
582 |
+
assert asinh(2*I + I*x - x**2).as_leading_term(x, cdir=-1) == log(2 - sqrt(3)) + I*pi/2
|
583 |
+
|
584 |
+
|
585 |
+
def test_asinh_series():
|
586 |
+
x = Symbol('x')
|
587 |
+
assert asinh(x).series(x, 0, 8) == \
|
588 |
+
x - x**3/6 + 3*x**5/40 - 5*x**7/112 + O(x**8)
|
589 |
+
t5 = asinh(x).taylor_term(5, x)
|
590 |
+
assert t5 == 3*x**5/40
|
591 |
+
assert asinh(x).taylor_term(7, x, t5, 0) == -5*x**7/112
|
592 |
+
|
593 |
+
|
594 |
+
def test_asinh_nseries():
|
595 |
+
x = Symbol('x')
|
596 |
+
# Tests concerning branch points
|
597 |
+
assert asinh(x + I)._eval_nseries(x, 4, None) == I*pi/2 + \
|
598 |
+
sqrt(x)*(1 - I) + x**(S(3)/2)*(S(1)/12 + I/12) + x**(S(5)/2)*(-S(3)/160 + 3*I/160) + \
|
599 |
+
x**(S(7)/2)*(-S(5)/896 - 5*I/896) + O(x**4)
|
600 |
+
assert asinh(x - I)._eval_nseries(x, 4, None) == -I*pi/2 + \
|
601 |
+
sqrt(x)*(1 + I) + x**(S(3)/2)*(S(1)/12 - I/12) + x**(S(5)/2)*(-S(3)/160 - 3*I/160) + \
|
602 |
+
x**(S(7)/2)*(-S(5)/896 + 5*I/896) + O(x**4)
|
603 |
+
# Tests concerning points lying on branch cuts
|
604 |
+
assert asinh(x + 2*I)._eval_nseries(x, 4, None, cdir=1) == I*asin(2) - \
|
605 |
+
sqrt(3)*I*x/3 + sqrt(3)*x**2/9 + sqrt(3)*I*x**3/18 + O(x**4)
|
606 |
+
assert asinh(x + 2*I)._eval_nseries(x, 4, None, cdir=-1) == I*pi - I*asin(2) + \
|
607 |
+
sqrt(3)*I*x/3 - sqrt(3)*x**2/9 - sqrt(3)*I*x**3/18 + O(x**4)
|
608 |
+
assert asinh(x - 2*I)._eval_nseries(x, 4, None, cdir=1) == I*asin(2) - I*pi + \
|
609 |
+
sqrt(3)*I*x/3 + sqrt(3)*x**2/9 - sqrt(3)*I*x**3/18 + O(x**4)
|
610 |
+
assert asinh(x - 2*I)._eval_nseries(x, 4, None, cdir=-1) == -I*asin(2) - \
|
611 |
+
sqrt(3)*I*x/3 - sqrt(3)*x**2/9 + sqrt(3)*I*x**3/18 + O(x**4)
|
612 |
+
# Tests concerning re(ndir) == 0
|
613 |
+
assert asinh(2*I + I*x - x**2)._eval_nseries(x, 4, None) == I*pi/2 + log(2 - sqrt(3)) - \
|
614 |
+
sqrt(3)*x/3 + x**2*(sqrt(3)/9 - sqrt(3)*I/3) + x**3*(-sqrt(3)/18 + 2*sqrt(3)*I/9) + O(x**4)
|
615 |
+
|
616 |
+
|
617 |
+
def test_asinh_fdiff():
|
618 |
+
x = Symbol('x')
|
619 |
+
raises(ArgumentIndexError, lambda: asinh(x).fdiff(2))
|
620 |
+
|
621 |
+
|
622 |
+
def test_acosh():
|
623 |
+
x = Symbol('x')
|
624 |
+
|
625 |
+
assert unchanged(acosh, -x)
|
626 |
+
|
627 |
+
#at specific points
|
628 |
+
assert acosh(1) == 0
|
629 |
+
assert acosh(-1) == pi*I
|
630 |
+
assert acosh(0) == I*pi/2
|
631 |
+
assert acosh(S.Half) == I*pi/3
|
632 |
+
assert acosh(Rational(-1, 2)) == pi*I*Rational(2, 3)
|
633 |
+
assert acosh(nan) is nan
|
634 |
+
|
635 |
+
# at infinites
|
636 |
+
assert acosh(oo) is oo
|
637 |
+
assert acosh(-oo) is oo
|
638 |
+
|
639 |
+
assert acosh(I*oo) == oo + I*pi/2
|
640 |
+
assert acosh(-I*oo) == oo - I*pi/2
|
641 |
+
|
642 |
+
assert acosh(zoo) is zoo
|
643 |
+
|
644 |
+
assert acosh(I) == log(I*(1 + sqrt(2)))
|
645 |
+
assert acosh(-I) == log(-I*(1 + sqrt(2)))
|
646 |
+
assert acosh((sqrt(3) - 1)/(2*sqrt(2))) == pi*I*Rational(5, 12)
|
647 |
+
assert acosh(-(sqrt(3) - 1)/(2*sqrt(2))) == pi*I*Rational(7, 12)
|
648 |
+
assert acosh(sqrt(2)/2) == I*pi/4
|
649 |
+
assert acosh(-sqrt(2)/2) == I*pi*Rational(3, 4)
|
650 |
+
assert acosh(sqrt(3)/2) == I*pi/6
|
651 |
+
assert acosh(-sqrt(3)/2) == I*pi*Rational(5, 6)
|
652 |
+
assert acosh(sqrt(2 + sqrt(2))/2) == I*pi/8
|
653 |
+
assert acosh(-sqrt(2 + sqrt(2))/2) == I*pi*Rational(7, 8)
|
654 |
+
assert acosh(sqrt(2 - sqrt(2))/2) == I*pi*Rational(3, 8)
|
655 |
+
assert acosh(-sqrt(2 - sqrt(2))/2) == I*pi*Rational(5, 8)
|
656 |
+
assert acosh((1 + sqrt(3))/(2*sqrt(2))) == I*pi/12
|
657 |
+
assert acosh(-(1 + sqrt(3))/(2*sqrt(2))) == I*pi*Rational(11, 12)
|
658 |
+
assert acosh((sqrt(5) + 1)/4) == I*pi/5
|
659 |
+
assert acosh(-(sqrt(5) + 1)/4) == I*pi*Rational(4, 5)
|
660 |
+
|
661 |
+
assert str(acosh(5*I).n(6)) == '2.31244 + 1.5708*I'
|
662 |
+
assert str(acosh(-5*I).n(6)) == '2.31244 - 1.5708*I'
|
663 |
+
|
664 |
+
# inverse composition
|
665 |
+
assert unchanged(acosh, Symbol('v1'))
|
666 |
+
|
667 |
+
assert acosh(cosh(-3, evaluate=False)) == 3
|
668 |
+
assert acosh(cosh(3, evaluate=False)) == 3
|
669 |
+
assert acosh(cosh(0, evaluate=False)) == 0
|
670 |
+
assert acosh(cosh(I, evaluate=False)) == I
|
671 |
+
assert acosh(cosh(-I, evaluate=False)) == I
|
672 |
+
assert acosh(cosh(7*I, evaluate=False)) == -2*I*pi + 7*I
|
673 |
+
assert acosh(cosh(1 + I)) == 1 + I
|
674 |
+
assert acosh(cosh(3 - 3*I)) == 3 - 3*I
|
675 |
+
assert acosh(cosh(-3 + 2*I)) == 3 - 2*I
|
676 |
+
assert acosh(cosh(-5 - 17*I)) == 5 - 6*I*pi + 17*I
|
677 |
+
assert acosh(cosh(-21 + 11*I)) == 21 - 11*I + 4*I*pi
|
678 |
+
assert acosh(cosh(cosh(1) + I)) == cosh(1) + I
|
679 |
+
assert acosh(1, evaluate=False).is_zero is True
|
680 |
+
|
681 |
+
|
682 |
+
def test_acosh_rewrite():
|
683 |
+
x = Symbol('x')
|
684 |
+
assert acosh(x).rewrite(log) == log(x + sqrt(x - 1)*sqrt(x + 1))
|
685 |
+
assert acosh(x).rewrite(asin) == sqrt(x - 1)*(-asin(x) + pi/2)/sqrt(1 - x)
|
686 |
+
assert acosh(x).rewrite(asinh) == sqrt(x - 1)*(-asin(x) + pi/2)/sqrt(1 - x)
|
687 |
+
assert acosh(x).rewrite(atanh) == \
|
688 |
+
(sqrt(x - 1)*sqrt(x + 1)*atanh(sqrt(x**2 - 1)/x)/sqrt(x**2 - 1) +
|
689 |
+
pi*sqrt(x - 1)*(-x*sqrt(x**(-2)) + 1)/(2*sqrt(1 - x)))
|
690 |
+
x = Symbol('x', positive=True)
|
691 |
+
assert acosh(x).rewrite(atanh) == \
|
692 |
+
sqrt(x - 1)*sqrt(x + 1)*atanh(sqrt(x**2 - 1)/x)/sqrt(x**2 - 1)
|
693 |
+
|
694 |
+
|
695 |
+
def test_acosh_leading_term():
|
696 |
+
x = Symbol('x')
|
697 |
+
# Tests concerning branch points
|
698 |
+
assert acosh(x).as_leading_term(x) == I*pi/2
|
699 |
+
assert acosh(x + 1).as_leading_term(x) == sqrt(2)*sqrt(x)
|
700 |
+
assert acosh(x - 1).as_leading_term(x) == I*pi
|
701 |
+
assert acosh(1/x).as_leading_term(x, cdir=1) == -log(x) + log(2)
|
702 |
+
assert acosh(1/x).as_leading_term(x, cdir=-1) == -log(x) + log(2) + 2*I*pi
|
703 |
+
# Tests concerning points lying on branch cuts
|
704 |
+
assert acosh(I*x - 2).as_leading_term(x, cdir=1) == acosh(-2)
|
705 |
+
assert acosh(-I*x - 2).as_leading_term(x, cdir=1) == -2*I*pi + acosh(-2)
|
706 |
+
assert acosh(x**2 - I*x + S(1)/3).as_leading_term(x, cdir=1) == -acosh(S(1)/3)
|
707 |
+
assert acosh(x**2 - I*x + S(1)/3).as_leading_term(x, cdir=-1) == acosh(S(1)/3)
|
708 |
+
assert acosh(1/(I*x - 3)).as_leading_term(x, cdir=1) == -acosh(-S(1)/3)
|
709 |
+
assert acosh(1/(I*x - 3)).as_leading_term(x, cdir=-1) == acosh(-S(1)/3)
|
710 |
+
# Tests concerning im(ndir) == 0
|
711 |
+
assert acosh(-I*x**2 + x - 2).as_leading_term(x, cdir=1) == log(sqrt(3) + 2) - I*pi
|
712 |
+
assert acosh(-I*x**2 + x - 2).as_leading_term(x, cdir=-1) == log(sqrt(3) + 2) - I*pi
|
713 |
+
|
714 |
+
|
715 |
+
def test_acosh_series():
|
716 |
+
x = Symbol('x')
|
717 |
+
assert acosh(x).series(x, 0, 8) == \
|
718 |
+
-I*x + pi*I/2 - I*x**3/6 - 3*I*x**5/40 - 5*I*x**7/112 + O(x**8)
|
719 |
+
t5 = acosh(x).taylor_term(5, x)
|
720 |
+
assert t5 == - 3*I*x**5/40
|
721 |
+
assert acosh(x).taylor_term(7, x, t5, 0) == - 5*I*x**7/112
|
722 |
+
|
723 |
+
|
724 |
+
def test_acosh_nseries():
|
725 |
+
x = Symbol('x')
|
726 |
+
# Tests concerning branch points
|
727 |
+
assert acosh(x + 1)._eval_nseries(x, 4, None) == sqrt(2)*sqrt(x) - \
|
728 |
+
sqrt(2)*x**(S(3)/2)/12 + 3*sqrt(2)*x**(S(5)/2)/160 - 5*sqrt(2)*x**(S(7)/2)/896 + O(x**4)
|
729 |
+
# Tests concerning points lying on branch cuts
|
730 |
+
assert acosh(x - 1)._eval_nseries(x, 4, None) == I*pi - \
|
731 |
+
sqrt(2)*I*sqrt(x) - sqrt(2)*I*x**(S(3)/2)/12 - 3*sqrt(2)*I*x**(S(5)/2)/160 - \
|
732 |
+
5*sqrt(2)*I*x**(S(7)/2)/896 + O(x**4)
|
733 |
+
assert acosh(I*x - 2)._eval_nseries(x, 4, None, cdir=1) == acosh(-2) - \
|
734 |
+
sqrt(3)*I*x/3 + sqrt(3)*x**2/9 + sqrt(3)*I*x**3/18 + O(x**4)
|
735 |
+
assert acosh(-I*x - 2)._eval_nseries(x, 4, None, cdir=1) == acosh(-2) - \
|
736 |
+
2*I*pi + sqrt(3)*I*x/3 + sqrt(3)*x**2/9 - sqrt(3)*I*x**3/18 + O(x**4)
|
737 |
+
assert acosh(1/(I*x - 3))._eval_nseries(x, 4, None, cdir=1) == -acosh(-S(1)/3) + \
|
738 |
+
sqrt(2)*x/12 + 17*sqrt(2)*I*x**2/576 - 443*sqrt(2)*x**3/41472 + O(x**4)
|
739 |
+
assert acosh(1/(I*x - 3))._eval_nseries(x, 4, None, cdir=-1) == acosh(-S(1)/3) - \
|
740 |
+
sqrt(2)*x/12 - 17*sqrt(2)*I*x**2/576 + 443*sqrt(2)*x**3/41472 + O(x**4)
|
741 |
+
# Tests concerning im(ndir) == 0
|
742 |
+
assert acosh(-I*x**2 + x - 2)._eval_nseries(x, 4, None) == -I*pi + log(sqrt(3) + 2) - \
|
743 |
+
sqrt(3)*x/3 + x**2*(-sqrt(3)/9 + sqrt(3)*I/3) + x**3*(-sqrt(3)/18 + 2*sqrt(3)*I/9) + O(x**4)
|
744 |
+
|
745 |
+
|
746 |
+
def test_acosh_fdiff():
|
747 |
+
x = Symbol('x')
|
748 |
+
raises(ArgumentIndexError, lambda: acosh(x).fdiff(2))
|
749 |
+
|
750 |
+
|
751 |
+
def test_asech():
|
752 |
+
x = Symbol('x')
|
753 |
+
|
754 |
+
assert unchanged(asech, -x)
|
755 |
+
|
756 |
+
# values at fixed points
|
757 |
+
assert asech(1) == 0
|
758 |
+
assert asech(-1) == pi*I
|
759 |
+
assert asech(0) is oo
|
760 |
+
assert asech(2) == I*pi/3
|
761 |
+
assert asech(-2) == 2*I*pi / 3
|
762 |
+
assert asech(nan) is nan
|
763 |
+
|
764 |
+
# at infinites
|
765 |
+
assert asech(oo) == I*pi/2
|
766 |
+
assert asech(-oo) == I*pi/2
|
767 |
+
assert asech(zoo) == I*AccumBounds(-pi/2, pi/2)
|
768 |
+
|
769 |
+
assert asech(I) == log(1 + sqrt(2)) - I*pi/2
|
770 |
+
assert asech(-I) == log(1 + sqrt(2)) + I*pi/2
|
771 |
+
assert asech(sqrt(2) - sqrt(6)) == 11*I*pi / 12
|
772 |
+
assert asech(sqrt(2 - 2/sqrt(5))) == I*pi / 10
|
773 |
+
assert asech(-sqrt(2 - 2/sqrt(5))) == 9*I*pi / 10
|
774 |
+
assert asech(2 / sqrt(2 + sqrt(2))) == I*pi / 8
|
775 |
+
assert asech(-2 / sqrt(2 + sqrt(2))) == 7*I*pi / 8
|
776 |
+
assert asech(sqrt(5) - 1) == I*pi / 5
|
777 |
+
assert asech(1 - sqrt(5)) == 4*I*pi / 5
|
778 |
+
assert asech(-sqrt(2*(2 + sqrt(2)))) == 5*I*pi / 8
|
779 |
+
|
780 |
+
# properties
|
781 |
+
# asech(x) == acosh(1/x)
|
782 |
+
assert asech(sqrt(2)) == acosh(1/sqrt(2))
|
783 |
+
assert asech(2/sqrt(3)) == acosh(sqrt(3)/2)
|
784 |
+
assert asech(2/sqrt(2 + sqrt(2))) == acosh(sqrt(2 + sqrt(2))/2)
|
785 |
+
assert asech(2) == acosh(S.Half)
|
786 |
+
|
787 |
+
# asech(x) == I*acos(1/x)
|
788 |
+
# (Note: the exact formula is asech(x) == +/- I*acos(1/x))
|
789 |
+
assert asech(-sqrt(2)) == I*acos(-1/sqrt(2))
|
790 |
+
assert asech(-2/sqrt(3)) == I*acos(-sqrt(3)/2)
|
791 |
+
assert asech(-S(2)) == I*acos(Rational(-1, 2))
|
792 |
+
assert asech(-2/sqrt(2)) == I*acos(-sqrt(2)/2)
|
793 |
+
|
794 |
+
# sech(asech(x)) / x == 1
|
795 |
+
assert expand_mul(sech(asech(sqrt(6) - sqrt(2))) / (sqrt(6) - sqrt(2))) == 1
|
796 |
+
assert expand_mul(sech(asech(sqrt(6) + sqrt(2))) / (sqrt(6) + sqrt(2))) == 1
|
797 |
+
assert (sech(asech(sqrt(2 + 2/sqrt(5)))) / (sqrt(2 + 2/sqrt(5)))).simplify() == 1
|
798 |
+
assert (sech(asech(-sqrt(2 + 2/sqrt(5)))) / (-sqrt(2 + 2/sqrt(5)))).simplify() == 1
|
799 |
+
assert (sech(asech(sqrt(2*(2 + sqrt(2))))) / (sqrt(2*(2 + sqrt(2))))).simplify() == 1
|
800 |
+
assert expand_mul(sech(asech(1 + sqrt(5))) / (1 + sqrt(5))) == 1
|
801 |
+
assert expand_mul(sech(asech(-1 - sqrt(5))) / (-1 - sqrt(5))) == 1
|
802 |
+
assert expand_mul(sech(asech(-sqrt(6) - sqrt(2))) / (-sqrt(6) - sqrt(2))) == 1
|
803 |
+
|
804 |
+
# numerical evaluation
|
805 |
+
assert str(asech(5*I).n(6)) == '0.19869 - 1.5708*I'
|
806 |
+
assert str(asech(-5*I).n(6)) == '0.19869 + 1.5708*I'
|
807 |
+
|
808 |
+
|
809 |
+
def test_asech_leading_term():
|
810 |
+
x = Symbol('x')
|
811 |
+
# Tests concerning branch points
|
812 |
+
assert asech(x).as_leading_term(x, cdir=1) == -log(x) + log(2)
|
813 |
+
assert asech(x).as_leading_term(x, cdir=-1) == -log(x) + log(2) + 2*I*pi
|
814 |
+
assert asech(x + 1).as_leading_term(x, cdir=1) == sqrt(2)*I*sqrt(x)
|
815 |
+
assert asech(1/x).as_leading_term(x, cdir=1) == I*pi/2
|
816 |
+
# Tests concerning points lying on branch cuts
|
817 |
+
assert asech(x - 1).as_leading_term(x, cdir=1) == I*pi
|
818 |
+
assert asech(I*x + 3).as_leading_term(x, cdir=1) == -asech(3)
|
819 |
+
assert asech(-I*x + 3).as_leading_term(x, cdir=1) == asech(3)
|
820 |
+
assert asech(I*x - 3).as_leading_term(x, cdir=1) == -asech(-3)
|
821 |
+
assert asech(-I*x - 3).as_leading_term(x, cdir=1) == asech(-3)
|
822 |
+
assert asech(I*x - S(1)/3).as_leading_term(x, cdir=1) == -2*I*pi + asech(-S(1)/3)
|
823 |
+
assert asech(I*x - S(1)/3).as_leading_term(x, cdir=-1) == asech(-S(1)/3)
|
824 |
+
# Tests concerning im(ndir) == 0
|
825 |
+
assert asech(-I*x**2 + x - 3).as_leading_term(x, cdir=1) == log(-S(1)/3 + 2*sqrt(2)*I/3)
|
826 |
+
assert asech(-I*x**2 + x - 3).as_leading_term(x, cdir=-1) == log(-S(1)/3 + 2*sqrt(2)*I/3)
|
827 |
+
|
828 |
+
|
829 |
+
def test_asech_series():
|
830 |
+
x = Symbol('x')
|
831 |
+
assert asech(x).series(x, 0, 9, cdir=1) == log(2) - log(x) - x**2/4 - 3*x**4/32 \
|
832 |
+
- 5*x**6/96 - 35*x**8/1024 + O(x**9)
|
833 |
+
assert asech(x).series(x, 0, 9, cdir=-1) == I*pi + log(2) - log(-x) - x**2/4 - \
|
834 |
+
3*x**4/32 - 5*x**6/96 - 35*x**8/1024 + O(x**9)
|
835 |
+
t6 = asech(x).taylor_term(6, x)
|
836 |
+
assert t6 == -5*x**6/96
|
837 |
+
assert asech(x).taylor_term(8, x, t6, 0) == -35*x**8/1024
|
838 |
+
|
839 |
+
|
840 |
+
def test_asech_nseries():
|
841 |
+
x = Symbol('x')
|
842 |
+
# Tests concerning branch points
|
843 |
+
assert asech(x + 1)._eval_nseries(x, 4, None) == sqrt(2)*sqrt(-x) + 5*sqrt(2)*(-x)**(S(3)/2)/12 + \
|
844 |
+
43*sqrt(2)*(-x)**(S(5)/2)/160 + 177*sqrt(2)*(-x)**(S(7)/2)/896 + O(x**4)
|
845 |
+
# Tests concerning points lying on branch cuts
|
846 |
+
assert asech(x - 1)._eval_nseries(x, 4, None) == I*pi + sqrt(2)*sqrt(x) + \
|
847 |
+
5*sqrt(2)*x**(S(3)/2)/12 + 43*sqrt(2)*x**(S(5)/2)/160 + 177*sqrt(2)*x**(S(7)/2)/896 + O(x**4)
|
848 |
+
assert asech(I*x + 3)._eval_nseries(x, 4, None) == -asech(3) + sqrt(2)*x/12 - \
|
849 |
+
17*sqrt(2)*I*x**2/576 - 443*sqrt(2)*x**3/41472 + O(x**4)
|
850 |
+
assert asech(-I*x + 3)._eval_nseries(x, 4, None) == asech(3) + sqrt(2)*x/12 + \
|
851 |
+
17*sqrt(2)*I*x**2/576 - 443*sqrt(2)*x**3/41472 + O(x**4)
|
852 |
+
assert asech(I*x - 3)._eval_nseries(x, 4, None) == -asech(-3) - sqrt(2)*x/12 - \
|
853 |
+
17*sqrt(2)*I*x**2/576 + 443*sqrt(2)*x**3/41472 + O(x**4)
|
854 |
+
assert asech(-I*x - 3)._eval_nseries(x, 4, None) == asech(-3) - sqrt(2)*x/12 + \
|
855 |
+
17*sqrt(2)*I*x**2/576 + 443*sqrt(2)*x**3/41472 + O(x**4)
|
856 |
+
# Tests concerning im(ndir) == 0
|
857 |
+
assert asech(-I*x**2 + x - 2)._eval_nseries(x, 3, None) == 2*I*pi/3 + sqrt(3)*I*x/6 + \
|
858 |
+
x**2*(sqrt(3)/6 + 7*sqrt(3)*I/72) + O(x**3)
|
859 |
+
|
860 |
+
|
861 |
+
def test_asech_rewrite():
|
862 |
+
x = Symbol('x')
|
863 |
+
assert asech(x).rewrite(log) == log(1/x + sqrt(1/x - 1) * sqrt(1/x + 1))
|
864 |
+
assert asech(x).rewrite(acosh) == acosh(1/x)
|
865 |
+
assert asech(x).rewrite(asinh) == sqrt(-1 + 1/x)*(-asin(1/x) + pi/2)/sqrt(1 - 1/x)
|
866 |
+
assert asech(x).rewrite(atanh) == \
|
867 |
+
sqrt(x + 1)*sqrt(1/(x + 1))*atanh(sqrt(1 - x**2)) + I*pi*(-sqrt(x)*sqrt(1/x) + 1 - I*sqrt(x**2)/(2*sqrt(-x**2)) - I*sqrt(-x)/(2*sqrt(x)))
|
868 |
+
|
869 |
+
|
870 |
+
def test_asech_fdiff():
|
871 |
+
x = Symbol('x')
|
872 |
+
raises(ArgumentIndexError, lambda: asech(x).fdiff(2))
|
873 |
+
|
874 |
+
|
875 |
+
def test_acsch():
|
876 |
+
x = Symbol('x')
|
877 |
+
|
878 |
+
assert unchanged(acsch, x)
|
879 |
+
assert acsch(-x) == -acsch(x)
|
880 |
+
|
881 |
+
# values at fixed points
|
882 |
+
assert acsch(1) == log(1 + sqrt(2))
|
883 |
+
assert acsch(-1) == - log(1 + sqrt(2))
|
884 |
+
assert acsch(0) is zoo
|
885 |
+
assert acsch(2) == log((1+sqrt(5))/2)
|
886 |
+
assert acsch(-2) == - log((1+sqrt(5))/2)
|
887 |
+
|
888 |
+
assert acsch(I) == - I*pi/2
|
889 |
+
assert acsch(-I) == I*pi/2
|
890 |
+
assert acsch(-I*(sqrt(6) + sqrt(2))) == I*pi / 12
|
891 |
+
assert acsch(I*(sqrt(2) + sqrt(6))) == -I*pi / 12
|
892 |
+
assert acsch(-I*(1 + sqrt(5))) == I*pi / 10
|
893 |
+
assert acsch(I*(1 + sqrt(5))) == -I*pi / 10
|
894 |
+
assert acsch(-I*2 / sqrt(2 - sqrt(2))) == I*pi / 8
|
895 |
+
assert acsch(I*2 / sqrt(2 - sqrt(2))) == -I*pi / 8
|
896 |
+
assert acsch(-I*2) == I*pi / 6
|
897 |
+
assert acsch(I*2) == -I*pi / 6
|
898 |
+
assert acsch(-I*sqrt(2 + 2/sqrt(5))) == I*pi / 5
|
899 |
+
assert acsch(I*sqrt(2 + 2/sqrt(5))) == -I*pi / 5
|
900 |
+
assert acsch(-I*sqrt(2)) == I*pi / 4
|
901 |
+
assert acsch(I*sqrt(2)) == -I*pi / 4
|
902 |
+
assert acsch(-I*(sqrt(5)-1)) == 3*I*pi / 10
|
903 |
+
assert acsch(I*(sqrt(5)-1)) == -3*I*pi / 10
|
904 |
+
assert acsch(-I*2 / sqrt(3)) == I*pi / 3
|
905 |
+
assert acsch(I*2 / sqrt(3)) == -I*pi / 3
|
906 |
+
assert acsch(-I*2 / sqrt(2 + sqrt(2))) == 3*I*pi / 8
|
907 |
+
assert acsch(I*2 / sqrt(2 + sqrt(2))) == -3*I*pi / 8
|
908 |
+
assert acsch(-I*sqrt(2 - 2/sqrt(5))) == 2*I*pi / 5
|
909 |
+
assert acsch(I*sqrt(2 - 2/sqrt(5))) == -2*I*pi / 5
|
910 |
+
assert acsch(-I*(sqrt(6) - sqrt(2))) == 5*I*pi / 12
|
911 |
+
assert acsch(I*(sqrt(6) - sqrt(2))) == -5*I*pi / 12
|
912 |
+
assert acsch(nan) is nan
|
913 |
+
|
914 |
+
# properties
|
915 |
+
# acsch(x) == asinh(1/x)
|
916 |
+
assert acsch(-I*sqrt(2)) == asinh(I/sqrt(2))
|
917 |
+
assert acsch(-I*2 / sqrt(3)) == asinh(I*sqrt(3) / 2)
|
918 |
+
|
919 |
+
# acsch(x) == -I*asin(I/x)
|
920 |
+
assert acsch(-I*sqrt(2)) == -I*asin(-1/sqrt(2))
|
921 |
+
assert acsch(-I*2 / sqrt(3)) == -I*asin(-sqrt(3)/2)
|
922 |
+
|
923 |
+
# csch(acsch(x)) / x == 1
|
924 |
+
assert expand_mul(csch(acsch(-I*(sqrt(6) + sqrt(2)))) / (-I*(sqrt(6) + sqrt(2)))) == 1
|
925 |
+
assert expand_mul(csch(acsch(I*(1 + sqrt(5)))) / (I*(1 + sqrt(5)))) == 1
|
926 |
+
assert (csch(acsch(I*sqrt(2 - 2/sqrt(5)))) / (I*sqrt(2 - 2/sqrt(5)))).simplify() == 1
|
927 |
+
assert (csch(acsch(-I*sqrt(2 - 2/sqrt(5)))) / (-I*sqrt(2 - 2/sqrt(5)))).simplify() == 1
|
928 |
+
|
929 |
+
# numerical evaluation
|
930 |
+
assert str(acsch(5*I+1).n(6)) == '0.0391819 - 0.193363*I'
|
931 |
+
assert str(acsch(-5*I+1).n(6)) == '0.0391819 + 0.193363*I'
|
932 |
+
|
933 |
+
|
934 |
+
def test_acsch_infinities():
|
935 |
+
assert acsch(oo) == 0
|
936 |
+
assert acsch(-oo) == 0
|
937 |
+
assert acsch(zoo) == 0
|
938 |
+
|
939 |
+
|
940 |
+
def test_acsch_leading_term():
|
941 |
+
x = Symbol('x')
|
942 |
+
assert acsch(1/x).as_leading_term(x) == x
|
943 |
+
# Tests concerning branch points
|
944 |
+
assert acsch(x + I).as_leading_term(x) == -I*pi/2
|
945 |
+
assert acsch(x - I).as_leading_term(x) == I*pi/2
|
946 |
+
# Tests concerning points lying on branch cuts
|
947 |
+
assert acsch(x).as_leading_term(x, cdir=1) == -log(x) + log(2)
|
948 |
+
assert acsch(x).as_leading_term(x, cdir=-1) == log(x) - log(2) - I*pi
|
949 |
+
assert acsch(x + I/2).as_leading_term(x, cdir=1) == -I*pi - acsch(I/2)
|
950 |
+
assert acsch(x + I/2).as_leading_term(x, cdir=-1) == acsch(I/2)
|
951 |
+
assert acsch(x - I/2).as_leading_term(x, cdir=1) == -acsch(I/2)
|
952 |
+
assert acsch(x - I/2).as_leading_term(x, cdir=-1) == acsch(I/2) + I*pi
|
953 |
+
# Tests concerning re(ndir) == 0
|
954 |
+
assert acsch(I/2 + I*x - x**2).as_leading_term(x, cdir=1) == log(2 - sqrt(3)) - I*pi/2
|
955 |
+
assert acsch(I/2 + I*x - x**2).as_leading_term(x, cdir=-1) == log(2 - sqrt(3)) - I*pi/2
|
956 |
+
|
957 |
+
|
958 |
+
def test_acsch_series():
|
959 |
+
x = Symbol('x')
|
960 |
+
assert acsch(x).series(x, 0, 9) == log(2) - log(x) + x**2/4 - 3*x**4/32 \
|
961 |
+
+ 5*x**6/96 - 35*x**8/1024 + O(x**9)
|
962 |
+
t4 = acsch(x).taylor_term(4, x)
|
963 |
+
assert t4 == -3*x**4/32
|
964 |
+
assert acsch(x).taylor_term(6, x, t4, 0) == 5*x**6/96
|
965 |
+
|
966 |
+
|
967 |
+
def test_acsch_nseries():
|
968 |
+
x = Symbol('x')
|
969 |
+
# Tests concerning branch points
|
970 |
+
assert acsch(x + I)._eval_nseries(x, 4, None) == -I*pi/2 + I*sqrt(x) + \
|
971 |
+
sqrt(x) + 5*I*x**(S(3)/2)/12 - 5*x**(S(3)/2)/12 - 43*I*x**(S(5)/2)/160 - \
|
972 |
+
43*x**(S(5)/2)/160 - 177*I*x**(S(7)/2)/896 + 177*x**(S(7)/2)/896 + O(x**4)
|
973 |
+
assert acsch(x - I)._eval_nseries(x, 4, None) == I*pi/2 - I*sqrt(x) + \
|
974 |
+
sqrt(x) - 5*I*x**(S(3)/2)/12 - 5*x**(S(3)/2)/12 + 43*I*x**(S(5)/2)/160 - \
|
975 |
+
43*x**(S(5)/2)/160 + 177*I*x**(S(7)/2)/896 + 177*x**(S(7)/2)/896 + O(x**4)
|
976 |
+
# Tests concerning points lying on branch cuts
|
977 |
+
assert acsch(x + I/2)._eval_nseries(x, 4, None, cdir=1) == -acsch(I/2) - \
|
978 |
+
I*pi + 4*sqrt(3)*I*x/3 - 8*sqrt(3)*x**2/9 - 16*sqrt(3)*I*x**3/9 + O(x**4)
|
979 |
+
assert acsch(x + I/2)._eval_nseries(x, 4, None, cdir=-1) == acsch(I/2) - \
|
980 |
+
4*sqrt(3)*I*x/3 + 8*sqrt(3)*x**2/9 + 16*sqrt(3)*I*x**3/9 + O(x**4)
|
981 |
+
assert acsch(x - I/2)._eval_nseries(x, 4, None, cdir=1) == -acsch(I/2) - \
|
982 |
+
4*sqrt(3)*I*x/3 - 8*sqrt(3)*x**2/9 + 16*sqrt(3)*I*x**3/9 + O(x**4)
|
983 |
+
assert acsch(x - I/2)._eval_nseries(x, 4, None, cdir=-1) == I*pi + \
|
984 |
+
acsch(I/2) + 4*sqrt(3)*I*x/3 + 8*sqrt(3)*x**2/9 - 16*sqrt(3)*I*x**3/9 + O(x**4)
|
985 |
+
# TODO: Tests concerning re(ndir) == 0
|
986 |
+
assert acsch(I/2 + I*x - x**2)._eval_nseries(x, 4, None) == -I*pi/2 + \
|
987 |
+
log(2 - sqrt(3)) + 4*sqrt(3)*x/3 + x**2*(-8*sqrt(3)/9 + 4*sqrt(3)*I/3) + \
|
988 |
+
x**3*(16*sqrt(3)/9 - 16*sqrt(3)*I/9) + O(x**4)
|
989 |
+
|
990 |
+
|
991 |
+
def test_acsch_rewrite():
|
992 |
+
x = Symbol('x')
|
993 |
+
assert acsch(x).rewrite(log) == log(1/x + sqrt(1/x**2 + 1))
|
994 |
+
assert acsch(x).rewrite(asinh) == asinh(1/x)
|
995 |
+
assert acsch(x).rewrite(atanh) == (sqrt(-x**2)*(-sqrt(-(x**2 + 1)**2)
|
996 |
+
*atanh(sqrt(x**2 + 1))/(x**2 + 1)
|
997 |
+
+ pi/2)/x)
|
998 |
+
|
999 |
+
|
1000 |
+
def test_acsch_fdiff():
|
1001 |
+
x = Symbol('x')
|
1002 |
+
raises(ArgumentIndexError, lambda: acsch(x).fdiff(2))
|
1003 |
+
|
1004 |
+
|
1005 |
+
def test_atanh():
|
1006 |
+
x = Symbol('x')
|
1007 |
+
|
1008 |
+
#at specific points
|
1009 |
+
assert atanh(0) == 0
|
1010 |
+
assert atanh(I) == I*pi/4
|
1011 |
+
assert atanh(-I) == -I*pi/4
|
1012 |
+
assert atanh(1) is oo
|
1013 |
+
assert atanh(-1) is -oo
|
1014 |
+
assert atanh(nan) is nan
|
1015 |
+
|
1016 |
+
# at infinites
|
1017 |
+
assert atanh(oo) == -I*pi/2
|
1018 |
+
assert atanh(-oo) == I*pi/2
|
1019 |
+
|
1020 |
+
assert atanh(I*oo) == I*pi/2
|
1021 |
+
assert atanh(-I*oo) == -I*pi/2
|
1022 |
+
|
1023 |
+
assert atanh(zoo) == I*AccumBounds(-pi/2, pi/2)
|
1024 |
+
|
1025 |
+
#properties
|
1026 |
+
assert atanh(-x) == -atanh(x)
|
1027 |
+
|
1028 |
+
assert atanh(I/sqrt(3)) == I*pi/6
|
1029 |
+
assert atanh(-I/sqrt(3)) == -I*pi/6
|
1030 |
+
assert atanh(I*sqrt(3)) == I*pi/3
|
1031 |
+
assert atanh(-I*sqrt(3)) == -I*pi/3
|
1032 |
+
assert atanh(I*(1 + sqrt(2))) == pi*I*Rational(3, 8)
|
1033 |
+
assert atanh(I*(sqrt(2) - 1)) == pi*I/8
|
1034 |
+
assert atanh(I*(1 - sqrt(2))) == -pi*I/8
|
1035 |
+
assert atanh(-I*(1 + sqrt(2))) == pi*I*Rational(-3, 8)
|
1036 |
+
assert atanh(I*sqrt(5 + 2*sqrt(5))) == I*pi*Rational(2, 5)
|
1037 |
+
assert atanh(-I*sqrt(5 + 2*sqrt(5))) == I*pi*Rational(-2, 5)
|
1038 |
+
assert atanh(I*(2 - sqrt(3))) == pi*I/12
|
1039 |
+
assert atanh(I*(sqrt(3) - 2)) == -pi*I/12
|
1040 |
+
assert atanh(oo) == -I*pi/2
|
1041 |
+
|
1042 |
+
# Symmetry
|
1043 |
+
assert atanh(Rational(-1, 2)) == -atanh(S.Half)
|
1044 |
+
|
1045 |
+
# inverse composition
|
1046 |
+
assert unchanged(atanh, tanh(Symbol('v1')))
|
1047 |
+
|
1048 |
+
assert atanh(tanh(-5, evaluate=False)) == -5
|
1049 |
+
assert atanh(tanh(0, evaluate=False)) == 0
|
1050 |
+
assert atanh(tanh(7, evaluate=False)) == 7
|
1051 |
+
assert atanh(tanh(I, evaluate=False)) == I
|
1052 |
+
assert atanh(tanh(-I, evaluate=False)) == -I
|
1053 |
+
assert atanh(tanh(-11*I, evaluate=False)) == -11*I + 4*I*pi
|
1054 |
+
assert atanh(tanh(3 + I)) == 3 + I
|
1055 |
+
assert atanh(tanh(4 + 5*I)) == 4 - 2*I*pi + 5*I
|
1056 |
+
assert atanh(tanh(pi/2)) == pi/2
|
1057 |
+
assert atanh(tanh(pi)) == pi
|
1058 |
+
assert atanh(tanh(-3 + 7*I)) == -3 - 2*I*pi + 7*I
|
1059 |
+
assert atanh(tanh(9 - I*2/3)) == 9 - I*2/3
|
1060 |
+
assert atanh(tanh(-32 - 123*I)) == -32 - 123*I + 39*I*pi
|
1061 |
+
|
1062 |
+
|
1063 |
+
def test_atanh_rewrite():
|
1064 |
+
x = Symbol('x')
|
1065 |
+
assert atanh(x).rewrite(log) == (log(1 + x) - log(1 - x)) / 2
|
1066 |
+
assert atanh(x).rewrite(asinh) == \
|
1067 |
+
pi*x/(2*sqrt(-x**2)) - sqrt(-x)*sqrt(1 - x**2)*sqrt(1/(x**2 - 1))*asinh(sqrt(1/(x**2 - 1)))/sqrt(x)
|
1068 |
+
|
1069 |
+
|
1070 |
+
def test_atanh_leading_term():
|
1071 |
+
x = Symbol('x')
|
1072 |
+
assert atanh(x).as_leading_term(x) == x
|
1073 |
+
# Tests concerning branch points
|
1074 |
+
assert atanh(x + 1).as_leading_term(x, cdir=1) == -log(x)/2 + log(2)/2 - I*pi/2
|
1075 |
+
assert atanh(x + 1).as_leading_term(x, cdir=-1) == -log(x)/2 + log(2)/2 + I*pi/2
|
1076 |
+
assert atanh(x - 1).as_leading_term(x, cdir=1) == log(x)/2 - log(2)/2
|
1077 |
+
assert atanh(x - 1).as_leading_term(x, cdir=-1) == log(x)/2 - log(2)/2
|
1078 |
+
assert atanh(1/x).as_leading_term(x, cdir=1) == -I*pi/2
|
1079 |
+
assert atanh(1/x).as_leading_term(x, cdir=-1) == I*pi/2
|
1080 |
+
# Tests concerning points lying on branch cuts
|
1081 |
+
assert atanh(I*x + 2).as_leading_term(x, cdir=1) == atanh(2) + I*pi
|
1082 |
+
assert atanh(-I*x + 2).as_leading_term(x, cdir=1) == atanh(2)
|
1083 |
+
assert atanh(I*x - 2).as_leading_term(x, cdir=1) == -atanh(2)
|
1084 |
+
assert atanh(-I*x - 2).as_leading_term(x, cdir=1) == -I*pi - atanh(2)
|
1085 |
+
# Tests concerning im(ndir) == 0
|
1086 |
+
assert atanh(-I*x**2 + x - 2).as_leading_term(x, cdir=1) == -log(3)/2 - I*pi/2
|
1087 |
+
assert atanh(-I*x**2 + x - 2).as_leading_term(x, cdir=-1) == -log(3)/2 - I*pi/2
|
1088 |
+
|
1089 |
+
|
1090 |
+
def test_atanh_series():
|
1091 |
+
x = Symbol('x')
|
1092 |
+
assert atanh(x).series(x, 0, 10) == \
|
1093 |
+
x + x**3/3 + x**5/5 + x**7/7 + x**9/9 + O(x**10)
|
1094 |
+
|
1095 |
+
|
1096 |
+
def test_atanh_nseries():
|
1097 |
+
x = Symbol('x')
|
1098 |
+
# Tests concerning branch points
|
1099 |
+
assert atanh(x + 1)._eval_nseries(x, 4, None, cdir=1) == -I*pi/2 + log(2)/2 - \
|
1100 |
+
log(x)/2 + x/4 - x**2/16 + x**3/48 + O(x**4)
|
1101 |
+
assert atanh(x + 1)._eval_nseries(x, 4, None, cdir=-1) == I*pi/2 + log(2)/2 - \
|
1102 |
+
log(x)/2 + x/4 - x**2/16 + x**3/48 + O(x**4)
|
1103 |
+
assert atanh(x - 1)._eval_nseries(x, 4, None, cdir=1) == -log(2)/2 + log(x)/2 + \
|
1104 |
+
x/4 + x**2/16 + x**3/48 + O(x**4)
|
1105 |
+
assert atanh(x - 1)._eval_nseries(x, 4, None, cdir=-1) == -log(2)/2 + log(x)/2 + \
|
1106 |
+
x/4 + x**2/16 + x**3/48 + O(x**4)
|
1107 |
+
# Tests concerning points lying on branch cuts
|
1108 |
+
assert atanh(I*x + 2)._eval_nseries(x, 4, None, cdir=1) == I*pi + atanh(2) - \
|
1109 |
+
I*x/3 - 2*x**2/9 + 13*I*x**3/81 + O(x**4)
|
1110 |
+
assert atanh(I*x + 2)._eval_nseries(x, 4, None, cdir=-1) == atanh(2) - I*x/3 - \
|
1111 |
+
2*x**2/9 + 13*I*x**3/81 + O(x**4)
|
1112 |
+
assert atanh(I*x - 2)._eval_nseries(x, 4, None, cdir=1) == -atanh(2) - I*x/3 + \
|
1113 |
+
2*x**2/9 + 13*I*x**3/81 + O(x**4)
|
1114 |
+
assert atanh(I*x - 2)._eval_nseries(x, 4, None, cdir=-1) == -atanh(2) - I*pi - \
|
1115 |
+
I*x/3 + 2*x**2/9 + 13*I*x**3/81 + O(x**4)
|
1116 |
+
# Tests concerning im(ndir) == 0
|
1117 |
+
assert atanh(-I*x**2 + x - 2)._eval_nseries(x, 4, None) == -I*pi/2 - log(3)/2 - x/3 + \
|
1118 |
+
x**2*(-S(1)/4 + I/2) + x**2*(S(1)/36 - I/6) + x**3*(-S(1)/6 + I/2) + x**3*(S(1)/162 - I/18) + O(x**4)
|
1119 |
+
|
1120 |
+
|
1121 |
+
def test_atanh_fdiff():
|
1122 |
+
x = Symbol('x')
|
1123 |
+
raises(ArgumentIndexError, lambda: atanh(x).fdiff(2))
|
1124 |
+
|
1125 |
+
|
1126 |
+
def test_acoth():
|
1127 |
+
x = Symbol('x')
|
1128 |
+
|
1129 |
+
#at specific points
|
1130 |
+
assert acoth(0) == I*pi/2
|
1131 |
+
assert acoth(I) == -I*pi/4
|
1132 |
+
assert acoth(-I) == I*pi/4
|
1133 |
+
assert acoth(1) is oo
|
1134 |
+
assert acoth(-1) is -oo
|
1135 |
+
assert acoth(nan) is nan
|
1136 |
+
|
1137 |
+
# at infinites
|
1138 |
+
assert acoth(oo) == 0
|
1139 |
+
assert acoth(-oo) == 0
|
1140 |
+
assert acoth(I*oo) == 0
|
1141 |
+
assert acoth(-I*oo) == 0
|
1142 |
+
assert acoth(zoo) == 0
|
1143 |
+
|
1144 |
+
#properties
|
1145 |
+
assert acoth(-x) == -acoth(x)
|
1146 |
+
|
1147 |
+
assert acoth(I/sqrt(3)) == -I*pi/3
|
1148 |
+
assert acoth(-I/sqrt(3)) == I*pi/3
|
1149 |
+
assert acoth(I*sqrt(3)) == -I*pi/6
|
1150 |
+
assert acoth(-I*sqrt(3)) == I*pi/6
|
1151 |
+
assert acoth(I*(1 + sqrt(2))) == -pi*I/8
|
1152 |
+
assert acoth(-I*(sqrt(2) + 1)) == pi*I/8
|
1153 |
+
assert acoth(I*(1 - sqrt(2))) == pi*I*Rational(3, 8)
|
1154 |
+
assert acoth(I*(sqrt(2) - 1)) == pi*I*Rational(-3, 8)
|
1155 |
+
assert acoth(I*sqrt(5 + 2*sqrt(5))) == -I*pi/10
|
1156 |
+
assert acoth(-I*sqrt(5 + 2*sqrt(5))) == I*pi/10
|
1157 |
+
assert acoth(I*(2 + sqrt(3))) == -pi*I/12
|
1158 |
+
assert acoth(-I*(2 + sqrt(3))) == pi*I/12
|
1159 |
+
assert acoth(I*(2 - sqrt(3))) == pi*I*Rational(-5, 12)
|
1160 |
+
assert acoth(I*(sqrt(3) - 2)) == pi*I*Rational(5, 12)
|
1161 |
+
|
1162 |
+
# Symmetry
|
1163 |
+
assert acoth(Rational(-1, 2)) == -acoth(S.Half)
|
1164 |
+
|
1165 |
+
|
1166 |
+
def test_acoth_rewrite():
|
1167 |
+
x = Symbol('x')
|
1168 |
+
assert acoth(x).rewrite(log) == (log(1 + 1/x) - log(1 - 1/x)) / 2
|
1169 |
+
assert acoth(x).rewrite(atanh) == atanh(1/x)
|
1170 |
+
assert acoth(x).rewrite(asinh) == \
|
1171 |
+
x*sqrt(x**(-2))*asinh(sqrt(1/(x**2 - 1))) + I*pi*(sqrt((x - 1)/x)*sqrt(x/(x - 1)) - sqrt(x/(x + 1))*sqrt(1 + 1/x))/2
|
1172 |
+
|
1173 |
+
|
1174 |
+
def test_acoth_leading_term():
|
1175 |
+
x = Symbol('x')
|
1176 |
+
# Tests concerning branch points
|
1177 |
+
assert acoth(x + 1).as_leading_term(x, cdir=1) == -log(x)/2 + log(2)/2
|
1178 |
+
assert acoth(x + 1).as_leading_term(x, cdir=-1) == -log(x)/2 + log(2)/2
|
1179 |
+
assert acoth(x - 1).as_leading_term(x, cdir=1) == log(x)/2 - log(2)/2 + I*pi/2
|
1180 |
+
assert acoth(x - 1).as_leading_term(x, cdir=-1) == log(x)/2 - log(2)/2 - I*pi/2
|
1181 |
+
# Tests concerning points lying on branch cuts
|
1182 |
+
assert acoth(x).as_leading_term(x, cdir=-1) == I*pi/2
|
1183 |
+
assert acoth(x).as_leading_term(x, cdir=1) == -I*pi/2
|
1184 |
+
assert acoth(I*x + 1/2).as_leading_term(x, cdir=1) == acoth(1/2)
|
1185 |
+
assert acoth(-I*x + 1/2).as_leading_term(x, cdir=1) == acoth(1/2) + I*pi
|
1186 |
+
assert acoth(I*x - 1/2).as_leading_term(x, cdir=1) == -I*pi - acoth(1/2)
|
1187 |
+
assert acoth(-I*x - 1/2).as_leading_term(x, cdir=1) == -acoth(1/2)
|
1188 |
+
# Tests concerning im(ndir) == 0
|
1189 |
+
assert acoth(-I*x**2 - x - S(1)/2).as_leading_term(x, cdir=1) == -log(3)/2 + I*pi/2
|
1190 |
+
assert acoth(-I*x**2 - x - S(1)/2).as_leading_term(x, cdir=-1) == -log(3)/2 + I*pi/2
|
1191 |
+
|
1192 |
+
|
1193 |
+
def test_acoth_series():
|
1194 |
+
x = Symbol('x')
|
1195 |
+
assert acoth(x).series(x, 0, 10) == \
|
1196 |
+
-I*pi/2 + x + x**3/3 + x**5/5 + x**7/7 + x**9/9 + O(x**10)
|
1197 |
+
|
1198 |
+
|
1199 |
+
def test_acoth_nseries():
|
1200 |
+
x = Symbol('x')
|
1201 |
+
# Tests concerning branch points
|
1202 |
+
assert acoth(x + 1)._eval_nseries(x, 4, None) == log(2)/2 - log(x)/2 + x/4 - \
|
1203 |
+
x**2/16 + x**3/48 + O(x**4)
|
1204 |
+
assert acoth(x - 1)._eval_nseries(x, 4, None, cdir=1) == I*pi/2 - log(2)/2 + \
|
1205 |
+
log(x)/2 + x/4 + x**2/16 + x**3/48 + O(x**4)
|
1206 |
+
assert acoth(x - 1)._eval_nseries(x, 4, None, cdir=-1) == -I*pi/2 - log(2)/2 + \
|
1207 |
+
log(x)/2 + x/4 + x**2/16 + x**3/48 + O(x**4)
|
1208 |
+
# Tests concerning points lying on branch cuts
|
1209 |
+
assert acoth(I*x + S(1)/2)._eval_nseries(x, 4, None, cdir=1) == acoth(S(1)/2) + \
|
1210 |
+
4*I*x/3 - 8*x**2/9 - 112*I*x**3/81 + O(x**4)
|
1211 |
+
assert acoth(I*x + S(1)/2)._eval_nseries(x, 4, None, cdir=-1) == I*pi + \
|
1212 |
+
acoth(S(1)/2) + 4*I*x/3 - 8*x**2/9 - 112*I*x**3/81 + O(x**4)
|
1213 |
+
assert acoth(I*x - S(1)/2)._eval_nseries(x, 4, None, cdir=1) == -acoth(S(1)/2) - \
|
1214 |
+
I*pi + 4*I*x/3 + 8*x**2/9 - 112*I*x**3/81 + O(x**4)
|
1215 |
+
assert acoth(I*x - S(1)/2)._eval_nseries(x, 4, None, cdir=-1) == -acoth(S(1)/2) + \
|
1216 |
+
4*I*x/3 + 8*x**2/9 - 112*I*x**3/81 + O(x**4)
|
1217 |
+
# Tests concerning im(ndir) == 0
|
1218 |
+
assert acoth(-I*x**2 - x - S(1)/2)._eval_nseries(x, 4, None) == I*pi/2 - log(3)/2 - \
|
1219 |
+
4*x/3 + x**2*(-S(8)/9 + 2*I/3) - 2*I*x**2 + x**3*(S(104)/81 - 16*I/9) - 8*x**3/3 + O(x**4)
|
1220 |
+
|
1221 |
+
|
1222 |
+
def test_acoth_fdiff():
|
1223 |
+
x = Symbol('x')
|
1224 |
+
raises(ArgumentIndexError, lambda: acoth(x).fdiff(2))
|
1225 |
+
|
1226 |
+
|
1227 |
+
def test_inverses():
|
1228 |
+
x = Symbol('x')
|
1229 |
+
assert sinh(x).inverse() == asinh
|
1230 |
+
raises(AttributeError, lambda: cosh(x).inverse())
|
1231 |
+
assert tanh(x).inverse() == atanh
|
1232 |
+
assert coth(x).inverse() == acoth
|
1233 |
+
assert asinh(x).inverse() == sinh
|
1234 |
+
assert acosh(x).inverse() == cosh
|
1235 |
+
assert atanh(x).inverse() == tanh
|
1236 |
+
assert acoth(x).inverse() == coth
|
1237 |
+
assert asech(x).inverse() == sech
|
1238 |
+
assert acsch(x).inverse() == csch
|
1239 |
+
|
1240 |
+
|
1241 |
+
def test_leading_term():
|
1242 |
+
x = Symbol('x')
|
1243 |
+
assert cosh(x).as_leading_term(x) == 1
|
1244 |
+
assert coth(x).as_leading_term(x) == 1/x
|
1245 |
+
for func in [sinh, tanh]:
|
1246 |
+
assert func(x).as_leading_term(x) == x
|
1247 |
+
for func in [sinh, cosh, tanh, coth]:
|
1248 |
+
for ar in (1/x, S.Half):
|
1249 |
+
eq = func(ar)
|
1250 |
+
assert eq.as_leading_term(x) == eq
|
1251 |
+
for func in [csch, sech]:
|
1252 |
+
eq = func(S.Half)
|
1253 |
+
assert eq.as_leading_term(x) == eq
|
1254 |
+
|
1255 |
+
|
1256 |
+
def test_complex():
|
1257 |
+
a, b = symbols('a,b', real=True)
|
1258 |
+
z = a + b*I
|
1259 |
+
for func in [sinh, cosh, tanh, coth, sech, csch]:
|
1260 |
+
assert func(z).conjugate() == func(a - b*I)
|
1261 |
+
for deep in [True, False]:
|
1262 |
+
assert sinh(z).expand(
|
1263 |
+
complex=True, deep=deep) == sinh(a)*cos(b) + I*cosh(a)*sin(b)
|
1264 |
+
assert cosh(z).expand(
|
1265 |
+
complex=True, deep=deep) == cosh(a)*cos(b) + I*sinh(a)*sin(b)
|
1266 |
+
assert tanh(z).expand(complex=True, deep=deep) == sinh(a)*cosh(
|
1267 |
+
a)/(cos(b)**2 + sinh(a)**2) + I*sin(b)*cos(b)/(cos(b)**2 + sinh(a)**2)
|
1268 |
+
assert coth(z).expand(complex=True, deep=deep) == sinh(a)*cosh(
|
1269 |
+
a)/(sin(b)**2 + sinh(a)**2) - I*sin(b)*cos(b)/(sin(b)**2 + sinh(a)**2)
|
1270 |
+
assert csch(z).expand(complex=True, deep=deep) == cos(b) * sinh(a) / (sin(b)**2\
|
1271 |
+
*cosh(a)**2 + cos(b)**2 * sinh(a)**2) - I*sin(b) * cosh(a) / (sin(b)**2\
|
1272 |
+
*cosh(a)**2 + cos(b)**2 * sinh(a)**2)
|
1273 |
+
assert sech(z).expand(complex=True, deep=deep) == cos(b) * cosh(a) / (sin(b)**2\
|
1274 |
+
*sinh(a)**2 + cos(b)**2 * cosh(a)**2) - I*sin(b) * sinh(a) / (sin(b)**2\
|
1275 |
+
*sinh(a)**2 + cos(b)**2 * cosh(a)**2)
|
1276 |
+
|
1277 |
+
|
1278 |
+
def test_complex_2899():
|
1279 |
+
a, b = symbols('a,b', real=True)
|
1280 |
+
for deep in [True, False]:
|
1281 |
+
for func in [sinh, cosh, tanh, coth]:
|
1282 |
+
assert func(a).expand(complex=True, deep=deep) == func(a)
|
1283 |
+
|
1284 |
+
|
1285 |
+
def test_simplifications():
|
1286 |
+
x = Symbol('x')
|
1287 |
+
assert sinh(asinh(x)) == x
|
1288 |
+
assert sinh(acosh(x)) == sqrt(x - 1) * sqrt(x + 1)
|
1289 |
+
assert sinh(atanh(x)) == x/sqrt(1 - x**2)
|
1290 |
+
assert sinh(acoth(x)) == 1/(sqrt(x - 1) * sqrt(x + 1))
|
1291 |
+
|
1292 |
+
assert cosh(asinh(x)) == sqrt(1 + x**2)
|
1293 |
+
assert cosh(acosh(x)) == x
|
1294 |
+
assert cosh(atanh(x)) == 1/sqrt(1 - x**2)
|
1295 |
+
assert cosh(acoth(x)) == x/(sqrt(x - 1) * sqrt(x + 1))
|
1296 |
+
|
1297 |
+
assert tanh(asinh(x)) == x/sqrt(1 + x**2)
|
1298 |
+
assert tanh(acosh(x)) == sqrt(x - 1) * sqrt(x + 1) / x
|
1299 |
+
assert tanh(atanh(x)) == x
|
1300 |
+
assert tanh(acoth(x)) == 1/x
|
1301 |
+
|
1302 |
+
assert coth(asinh(x)) == sqrt(1 + x**2)/x
|
1303 |
+
assert coth(acosh(x)) == x/(sqrt(x - 1) * sqrt(x + 1))
|
1304 |
+
assert coth(atanh(x)) == 1/x
|
1305 |
+
assert coth(acoth(x)) == x
|
1306 |
+
|
1307 |
+
assert csch(asinh(x)) == 1/x
|
1308 |
+
assert csch(acosh(x)) == 1/(sqrt(x - 1) * sqrt(x + 1))
|
1309 |
+
assert csch(atanh(x)) == sqrt(1 - x**2)/x
|
1310 |
+
assert csch(acoth(x)) == sqrt(x - 1) * sqrt(x + 1)
|
1311 |
+
|
1312 |
+
assert sech(asinh(x)) == 1/sqrt(1 + x**2)
|
1313 |
+
assert sech(acosh(x)) == 1/x
|
1314 |
+
assert sech(atanh(x)) == sqrt(1 - x**2)
|
1315 |
+
assert sech(acoth(x)) == sqrt(x - 1) * sqrt(x + 1)/x
|
1316 |
+
|
1317 |
+
|
1318 |
+
def test_issue_4136():
|
1319 |
+
assert cosh(asinh(Integer(3)/2)) == sqrt(Integer(13)/4)
|
1320 |
+
|
1321 |
+
|
1322 |
+
def test_sinh_rewrite():
|
1323 |
+
x = Symbol('x')
|
1324 |
+
assert sinh(x).rewrite(exp) == (exp(x) - exp(-x))/2 \
|
1325 |
+
== sinh(x).rewrite('tractable')
|
1326 |
+
assert sinh(x).rewrite(cosh) == -I*cosh(x + I*pi/2)
|
1327 |
+
tanh_half = tanh(S.Half*x)
|
1328 |
+
assert sinh(x).rewrite(tanh) == 2*tanh_half/(1 - tanh_half**2)
|
1329 |
+
coth_half = coth(S.Half*x)
|
1330 |
+
assert sinh(x).rewrite(coth) == 2*coth_half/(coth_half**2 - 1)
|
1331 |
+
|
1332 |
+
|
1333 |
+
def test_cosh_rewrite():
|
1334 |
+
x = Symbol('x')
|
1335 |
+
assert cosh(x).rewrite(exp) == (exp(x) + exp(-x))/2 \
|
1336 |
+
== cosh(x).rewrite('tractable')
|
1337 |
+
assert cosh(x).rewrite(sinh) == -I*sinh(x + I*pi/2)
|
1338 |
+
tanh_half = tanh(S.Half*x)**2
|
1339 |
+
assert cosh(x).rewrite(tanh) == (1 + tanh_half)/(1 - tanh_half)
|
1340 |
+
coth_half = coth(S.Half*x)**2
|
1341 |
+
assert cosh(x).rewrite(coth) == (coth_half + 1)/(coth_half - 1)
|
1342 |
+
|
1343 |
+
|
1344 |
+
def test_tanh_rewrite():
|
1345 |
+
x = Symbol('x')
|
1346 |
+
assert tanh(x).rewrite(exp) == (exp(x) - exp(-x))/(exp(x) + exp(-x)) \
|
1347 |
+
== tanh(x).rewrite('tractable')
|
1348 |
+
assert tanh(x).rewrite(sinh) == I*sinh(x)/sinh(I*pi/2 - x)
|
1349 |
+
assert tanh(x).rewrite(cosh) == I*cosh(I*pi/2 - x)/cosh(x)
|
1350 |
+
assert tanh(x).rewrite(coth) == 1/coth(x)
|
1351 |
+
|
1352 |
+
|
1353 |
+
def test_coth_rewrite():
|
1354 |
+
x = Symbol('x')
|
1355 |
+
assert coth(x).rewrite(exp) == (exp(x) + exp(-x))/(exp(x) - exp(-x)) \
|
1356 |
+
== coth(x).rewrite('tractable')
|
1357 |
+
assert coth(x).rewrite(sinh) == -I*sinh(I*pi/2 - x)/sinh(x)
|
1358 |
+
assert coth(x).rewrite(cosh) == -I*cosh(x)/cosh(I*pi/2 - x)
|
1359 |
+
assert coth(x).rewrite(tanh) == 1/tanh(x)
|
1360 |
+
|
1361 |
+
|
1362 |
+
def test_csch_rewrite():
|
1363 |
+
x = Symbol('x')
|
1364 |
+
assert csch(x).rewrite(exp) == 1 / (exp(x)/2 - exp(-x)/2) \
|
1365 |
+
== csch(x).rewrite('tractable')
|
1366 |
+
assert csch(x).rewrite(cosh) == I/cosh(x + I*pi/2)
|
1367 |
+
tanh_half = tanh(S.Half*x)
|
1368 |
+
assert csch(x).rewrite(tanh) == (1 - tanh_half**2)/(2*tanh_half)
|
1369 |
+
coth_half = coth(S.Half*x)
|
1370 |
+
assert csch(x).rewrite(coth) == (coth_half**2 - 1)/(2*coth_half)
|
1371 |
+
|
1372 |
+
|
1373 |
+
def test_sech_rewrite():
|
1374 |
+
x = Symbol('x')
|
1375 |
+
assert sech(x).rewrite(exp) == 1 / (exp(x)/2 + exp(-x)/2) \
|
1376 |
+
== sech(x).rewrite('tractable')
|
1377 |
+
assert sech(x).rewrite(sinh) == I/sinh(x + I*pi/2)
|
1378 |
+
tanh_half = tanh(S.Half*x)**2
|
1379 |
+
assert sech(x).rewrite(tanh) == (1 - tanh_half)/(1 + tanh_half)
|
1380 |
+
coth_half = coth(S.Half*x)**2
|
1381 |
+
assert sech(x).rewrite(coth) == (coth_half - 1)/(coth_half + 1)
|
1382 |
+
|
1383 |
+
|
1384 |
+
def test_derivs():
|
1385 |
+
x = Symbol('x')
|
1386 |
+
assert coth(x).diff(x) == -sinh(x)**(-2)
|
1387 |
+
assert sinh(x).diff(x) == cosh(x)
|
1388 |
+
assert cosh(x).diff(x) == sinh(x)
|
1389 |
+
assert tanh(x).diff(x) == -tanh(x)**2 + 1
|
1390 |
+
assert csch(x).diff(x) == -coth(x)*csch(x)
|
1391 |
+
assert sech(x).diff(x) == -tanh(x)*sech(x)
|
1392 |
+
assert acoth(x).diff(x) == 1/(-x**2 + 1)
|
1393 |
+
assert asinh(x).diff(x) == 1/sqrt(x**2 + 1)
|
1394 |
+
assert acosh(x).diff(x) == 1/(sqrt(x - 1)*sqrt(x + 1))
|
1395 |
+
assert acosh(x).diff(x) == acosh(x).rewrite(log).diff(x).together()
|
1396 |
+
assert atanh(x).diff(x) == 1/(-x**2 + 1)
|
1397 |
+
assert asech(x).diff(x) == -1/(x*sqrt(1 - x**2))
|
1398 |
+
assert acsch(x).diff(x) == -1/(x**2*sqrt(1 + x**(-2)))
|
1399 |
+
|
1400 |
+
|
1401 |
+
def test_sinh_expansion():
|
1402 |
+
x, y = symbols('x,y')
|
1403 |
+
assert sinh(x+y).expand(trig=True) == sinh(x)*cosh(y) + cosh(x)*sinh(y)
|
1404 |
+
assert sinh(2*x).expand(trig=True) == 2*sinh(x)*cosh(x)
|
1405 |
+
assert sinh(3*x).expand(trig=True).expand() == \
|
1406 |
+
sinh(x)**3 + 3*sinh(x)*cosh(x)**2
|
1407 |
+
|
1408 |
+
|
1409 |
+
def test_cosh_expansion():
|
1410 |
+
x, y = symbols('x,y')
|
1411 |
+
assert cosh(x+y).expand(trig=True) == cosh(x)*cosh(y) + sinh(x)*sinh(y)
|
1412 |
+
assert cosh(2*x).expand(trig=True) == cosh(x)**2 + sinh(x)**2
|
1413 |
+
assert cosh(3*x).expand(trig=True).expand() == \
|
1414 |
+
3*sinh(x)**2*cosh(x) + cosh(x)**3
|
1415 |
+
|
1416 |
+
def test_cosh_positive():
|
1417 |
+
# See issue 11721
|
1418 |
+
# cosh(x) is positive for real values of x
|
1419 |
+
k = symbols('k', real=True)
|
1420 |
+
n = symbols('n', integer=True)
|
1421 |
+
|
1422 |
+
assert cosh(k, evaluate=False).is_positive is True
|
1423 |
+
assert cosh(k + 2*n*pi*I, evaluate=False).is_positive is True
|
1424 |
+
assert cosh(I*pi/4, evaluate=False).is_positive is True
|
1425 |
+
assert cosh(3*I*pi/4, evaluate=False).is_positive is False
|
1426 |
+
|
1427 |
+
def test_cosh_nonnegative():
|
1428 |
+
k = symbols('k', real=True)
|
1429 |
+
n = symbols('n', integer=True)
|
1430 |
+
|
1431 |
+
assert cosh(k, evaluate=False).is_nonnegative is True
|
1432 |
+
assert cosh(k + 2*n*pi*I, evaluate=False).is_nonnegative is True
|
1433 |
+
assert cosh(I*pi/4, evaluate=False).is_nonnegative is True
|
1434 |
+
assert cosh(3*I*pi/4, evaluate=False).is_nonnegative is False
|
1435 |
+
assert cosh(S.Zero, evaluate=False).is_nonnegative is True
|
1436 |
+
|
1437 |
+
def test_real_assumptions():
|
1438 |
+
z = Symbol('z', real=False)
|
1439 |
+
assert sinh(z).is_real is None
|
1440 |
+
assert cosh(z).is_real is None
|
1441 |
+
assert tanh(z).is_real is None
|
1442 |
+
assert sech(z).is_real is None
|
1443 |
+
assert csch(z).is_real is None
|
1444 |
+
assert coth(z).is_real is None
|
1445 |
+
|
1446 |
+
def test_sign_assumptions():
|
1447 |
+
p = Symbol('p', positive=True)
|
1448 |
+
n = Symbol('n', negative=True)
|
1449 |
+
assert sinh(n).is_negative is True
|
1450 |
+
assert sinh(p).is_positive is True
|
1451 |
+
assert cosh(n).is_positive is True
|
1452 |
+
assert cosh(p).is_positive is True
|
1453 |
+
assert tanh(n).is_negative is True
|
1454 |
+
assert tanh(p).is_positive is True
|
1455 |
+
assert csch(n).is_negative is True
|
1456 |
+
assert csch(p).is_positive is True
|
1457 |
+
assert sech(n).is_positive is True
|
1458 |
+
assert sech(p).is_positive is True
|
1459 |
+
assert coth(n).is_negative is True
|
1460 |
+
assert coth(p).is_positive is True
|
venv/lib/python3.10/site-packages/sympy/functions/elementary/tests/test_integers.py
ADDED
@@ -0,0 +1,632 @@
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|
|
|
1 |
+
from sympy.calculus.accumulationbounds import AccumBounds
|
2 |
+
from sympy.core.numbers import (E, Float, I, Rational, nan, oo, pi, zoo)
|
3 |
+
from sympy.core.relational import (Eq, Ge, Gt, Le, Lt, Ne)
|
4 |
+
from sympy.core.singleton import S
|
5 |
+
from sympy.core.symbol import (Symbol, symbols)
|
6 |
+
from sympy.functions.combinatorial.factorials import factorial
|
7 |
+
from sympy.functions.elementary.exponential import (exp, log)
|
8 |
+
from sympy.functions.elementary.integers import (ceiling, floor, frac)
|
9 |
+
from sympy.functions.elementary.miscellaneous import sqrt
|
10 |
+
from sympy.functions.elementary.trigonometric import sin, cos, tan
|
11 |
+
|
12 |
+
from sympy.core.expr import unchanged
|
13 |
+
from sympy.testing.pytest import XFAIL
|
14 |
+
|
15 |
+
x = Symbol('x')
|
16 |
+
i = Symbol('i', imaginary=True)
|
17 |
+
y = Symbol('y', real=True)
|
18 |
+
k, n = symbols('k,n', integer=True)
|
19 |
+
|
20 |
+
|
21 |
+
def test_floor():
|
22 |
+
|
23 |
+
assert floor(nan) is nan
|
24 |
+
|
25 |
+
assert floor(oo) is oo
|
26 |
+
assert floor(-oo) is -oo
|
27 |
+
assert floor(zoo) is zoo
|
28 |
+
|
29 |
+
assert floor(0) == 0
|
30 |
+
|
31 |
+
assert floor(1) == 1
|
32 |
+
assert floor(-1) == -1
|
33 |
+
|
34 |
+
assert floor(E) == 2
|
35 |
+
assert floor(-E) == -3
|
36 |
+
|
37 |
+
assert floor(2*E) == 5
|
38 |
+
assert floor(-2*E) == -6
|
39 |
+
|
40 |
+
assert floor(pi) == 3
|
41 |
+
assert floor(-pi) == -4
|
42 |
+
|
43 |
+
assert floor(S.Half) == 0
|
44 |
+
assert floor(Rational(-1, 2)) == -1
|
45 |
+
|
46 |
+
assert floor(Rational(7, 3)) == 2
|
47 |
+
assert floor(Rational(-7, 3)) == -3
|
48 |
+
assert floor(-Rational(7, 3)) == -3
|
49 |
+
|
50 |
+
assert floor(Float(17.0)) == 17
|
51 |
+
assert floor(-Float(17.0)) == -17
|
52 |
+
|
53 |
+
assert floor(Float(7.69)) == 7
|
54 |
+
assert floor(-Float(7.69)) == -8
|
55 |
+
|
56 |
+
assert floor(I) == I
|
57 |
+
assert floor(-I) == -I
|
58 |
+
e = floor(i)
|
59 |
+
assert e.func is floor and e.args[0] == i
|
60 |
+
|
61 |
+
assert floor(oo*I) == oo*I
|
62 |
+
assert floor(-oo*I) == -oo*I
|
63 |
+
assert floor(exp(I*pi/4)*oo) == exp(I*pi/4)*oo
|
64 |
+
|
65 |
+
assert floor(2*I) == 2*I
|
66 |
+
assert floor(-2*I) == -2*I
|
67 |
+
|
68 |
+
assert floor(I/2) == 0
|
69 |
+
assert floor(-I/2) == -I
|
70 |
+
|
71 |
+
assert floor(E + 17) == 19
|
72 |
+
assert floor(pi + 2) == 5
|
73 |
+
|
74 |
+
assert floor(E + pi) == 5
|
75 |
+
assert floor(I + pi) == 3 + I
|
76 |
+
|
77 |
+
assert floor(floor(pi)) == 3
|
78 |
+
assert floor(floor(y)) == floor(y)
|
79 |
+
assert floor(floor(x)) == floor(x)
|
80 |
+
|
81 |
+
assert unchanged(floor, x)
|
82 |
+
assert unchanged(floor, 2*x)
|
83 |
+
assert unchanged(floor, k*x)
|
84 |
+
|
85 |
+
assert floor(k) == k
|
86 |
+
assert floor(2*k) == 2*k
|
87 |
+
assert floor(k*n) == k*n
|
88 |
+
|
89 |
+
assert unchanged(floor, k/2)
|
90 |
+
|
91 |
+
assert unchanged(floor, x + y)
|
92 |
+
|
93 |
+
assert floor(x + 3) == floor(x) + 3
|
94 |
+
assert floor(x + k) == floor(x) + k
|
95 |
+
|
96 |
+
assert floor(y + 3) == floor(y) + 3
|
97 |
+
assert floor(y + k) == floor(y) + k
|
98 |
+
|
99 |
+
assert floor(3 + I*y + pi) == 6 + floor(y)*I
|
100 |
+
|
101 |
+
assert floor(k + n) == k + n
|
102 |
+
|
103 |
+
assert unchanged(floor, x*I)
|
104 |
+
assert floor(k*I) == k*I
|
105 |
+
|
106 |
+
assert floor(Rational(23, 10) - E*I) == 2 - 3*I
|
107 |
+
|
108 |
+
assert floor(sin(1)) == 0
|
109 |
+
assert floor(sin(-1)) == -1
|
110 |
+
|
111 |
+
assert floor(exp(2)) == 7
|
112 |
+
|
113 |
+
assert floor(log(8)/log(2)) != 2
|
114 |
+
assert int(floor(log(8)/log(2)).evalf(chop=True)) == 3
|
115 |
+
|
116 |
+
assert floor(factorial(50)/exp(1)) == \
|
117 |
+
11188719610782480504630258070757734324011354208865721592720336800
|
118 |
+
|
119 |
+
assert (floor(y) < y) == False
|
120 |
+
assert (floor(y) <= y) == True
|
121 |
+
assert (floor(y) > y) == False
|
122 |
+
assert (floor(y) >= y) == False
|
123 |
+
assert (floor(x) <= x).is_Relational # x could be non-real
|
124 |
+
assert (floor(x) > x).is_Relational
|
125 |
+
assert (floor(x) <= y).is_Relational # arg is not same as rhs
|
126 |
+
assert (floor(x) > y).is_Relational
|
127 |
+
assert (floor(y) <= oo) == True
|
128 |
+
assert (floor(y) < oo) == True
|
129 |
+
assert (floor(y) >= -oo) == True
|
130 |
+
assert (floor(y) > -oo) == True
|
131 |
+
|
132 |
+
assert floor(y).rewrite(frac) == y - frac(y)
|
133 |
+
assert floor(y).rewrite(ceiling) == -ceiling(-y)
|
134 |
+
assert floor(y).rewrite(frac).subs(y, -pi) == floor(-pi)
|
135 |
+
assert floor(y).rewrite(frac).subs(y, E) == floor(E)
|
136 |
+
assert floor(y).rewrite(ceiling).subs(y, E) == -ceiling(-E)
|
137 |
+
assert floor(y).rewrite(ceiling).subs(y, -pi) == -ceiling(pi)
|
138 |
+
|
139 |
+
assert Eq(floor(y), y - frac(y))
|
140 |
+
assert Eq(floor(y), -ceiling(-y))
|
141 |
+
|
142 |
+
neg = Symbol('neg', negative=True)
|
143 |
+
nn = Symbol('nn', nonnegative=True)
|
144 |
+
pos = Symbol('pos', positive=True)
|
145 |
+
np = Symbol('np', nonpositive=True)
|
146 |
+
|
147 |
+
assert (floor(neg) < 0) == True
|
148 |
+
assert (floor(neg) <= 0) == True
|
149 |
+
assert (floor(neg) > 0) == False
|
150 |
+
assert (floor(neg) >= 0) == False
|
151 |
+
assert (floor(neg) <= -1) == True
|
152 |
+
assert (floor(neg) >= -3) == (neg >= -3)
|
153 |
+
assert (floor(neg) < 5) == (neg < 5)
|
154 |
+
|
155 |
+
assert (floor(nn) < 0) == False
|
156 |
+
assert (floor(nn) >= 0) == True
|
157 |
+
|
158 |
+
assert (floor(pos) < 0) == False
|
159 |
+
assert (floor(pos) <= 0) == (pos < 1)
|
160 |
+
assert (floor(pos) > 0) == (pos >= 1)
|
161 |
+
assert (floor(pos) >= 0) == True
|
162 |
+
assert (floor(pos) >= 3) == (pos >= 3)
|
163 |
+
|
164 |
+
assert (floor(np) <= 0) == True
|
165 |
+
assert (floor(np) > 0) == False
|
166 |
+
|
167 |
+
assert floor(neg).is_negative == True
|
168 |
+
assert floor(neg).is_nonnegative == False
|
169 |
+
assert floor(nn).is_negative == False
|
170 |
+
assert floor(nn).is_nonnegative == True
|
171 |
+
assert floor(pos).is_negative == False
|
172 |
+
assert floor(pos).is_nonnegative == True
|
173 |
+
assert floor(np).is_negative is None
|
174 |
+
assert floor(np).is_nonnegative is None
|
175 |
+
|
176 |
+
assert (floor(7, evaluate=False) >= 7) == True
|
177 |
+
assert (floor(7, evaluate=False) > 7) == False
|
178 |
+
assert (floor(7, evaluate=False) <= 7) == True
|
179 |
+
assert (floor(7, evaluate=False) < 7) == False
|
180 |
+
|
181 |
+
assert (floor(7, evaluate=False) >= 6) == True
|
182 |
+
assert (floor(7, evaluate=False) > 6) == True
|
183 |
+
assert (floor(7, evaluate=False) <= 6) == False
|
184 |
+
assert (floor(7, evaluate=False) < 6) == False
|
185 |
+
|
186 |
+
assert (floor(7, evaluate=False) >= 8) == False
|
187 |
+
assert (floor(7, evaluate=False) > 8) == False
|
188 |
+
assert (floor(7, evaluate=False) <= 8) == True
|
189 |
+
assert (floor(7, evaluate=False) < 8) == True
|
190 |
+
|
191 |
+
assert (floor(x) <= 5.5) == Le(floor(x), 5.5, evaluate=False)
|
192 |
+
assert (floor(x) >= -3.2) == Ge(floor(x), -3.2, evaluate=False)
|
193 |
+
assert (floor(x) < 2.9) == Lt(floor(x), 2.9, evaluate=False)
|
194 |
+
assert (floor(x) > -1.7) == Gt(floor(x), -1.7, evaluate=False)
|
195 |
+
|
196 |
+
assert (floor(y) <= 5.5) == (y < 6)
|
197 |
+
assert (floor(y) >= -3.2) == (y >= -3)
|
198 |
+
assert (floor(y) < 2.9) == (y < 3)
|
199 |
+
assert (floor(y) > -1.7) == (y >= -1)
|
200 |
+
|
201 |
+
assert (floor(y) <= n) == (y < n + 1)
|
202 |
+
assert (floor(y) >= n) == (y >= n)
|
203 |
+
assert (floor(y) < n) == (y < n)
|
204 |
+
assert (floor(y) > n) == (y >= n + 1)
|
205 |
+
|
206 |
+
|
207 |
+
def test_ceiling():
|
208 |
+
|
209 |
+
assert ceiling(nan) is nan
|
210 |
+
|
211 |
+
assert ceiling(oo) is oo
|
212 |
+
assert ceiling(-oo) is -oo
|
213 |
+
assert ceiling(zoo) is zoo
|
214 |
+
|
215 |
+
assert ceiling(0) == 0
|
216 |
+
|
217 |
+
assert ceiling(1) == 1
|
218 |
+
assert ceiling(-1) == -1
|
219 |
+
|
220 |
+
assert ceiling(E) == 3
|
221 |
+
assert ceiling(-E) == -2
|
222 |
+
|
223 |
+
assert ceiling(2*E) == 6
|
224 |
+
assert ceiling(-2*E) == -5
|
225 |
+
|
226 |
+
assert ceiling(pi) == 4
|
227 |
+
assert ceiling(-pi) == -3
|
228 |
+
|
229 |
+
assert ceiling(S.Half) == 1
|
230 |
+
assert ceiling(Rational(-1, 2)) == 0
|
231 |
+
|
232 |
+
assert ceiling(Rational(7, 3)) == 3
|
233 |
+
assert ceiling(-Rational(7, 3)) == -2
|
234 |
+
|
235 |
+
assert ceiling(Float(17.0)) == 17
|
236 |
+
assert ceiling(-Float(17.0)) == -17
|
237 |
+
|
238 |
+
assert ceiling(Float(7.69)) == 8
|
239 |
+
assert ceiling(-Float(7.69)) == -7
|
240 |
+
|
241 |
+
assert ceiling(I) == I
|
242 |
+
assert ceiling(-I) == -I
|
243 |
+
e = ceiling(i)
|
244 |
+
assert e.func is ceiling and e.args[0] == i
|
245 |
+
|
246 |
+
assert ceiling(oo*I) == oo*I
|
247 |
+
assert ceiling(-oo*I) == -oo*I
|
248 |
+
assert ceiling(exp(I*pi/4)*oo) == exp(I*pi/4)*oo
|
249 |
+
|
250 |
+
assert ceiling(2*I) == 2*I
|
251 |
+
assert ceiling(-2*I) == -2*I
|
252 |
+
|
253 |
+
assert ceiling(I/2) == I
|
254 |
+
assert ceiling(-I/2) == 0
|
255 |
+
|
256 |
+
assert ceiling(E + 17) == 20
|
257 |
+
assert ceiling(pi + 2) == 6
|
258 |
+
|
259 |
+
assert ceiling(E + pi) == 6
|
260 |
+
assert ceiling(I + pi) == I + 4
|
261 |
+
|
262 |
+
assert ceiling(ceiling(pi)) == 4
|
263 |
+
assert ceiling(ceiling(y)) == ceiling(y)
|
264 |
+
assert ceiling(ceiling(x)) == ceiling(x)
|
265 |
+
|
266 |
+
assert unchanged(ceiling, x)
|
267 |
+
assert unchanged(ceiling, 2*x)
|
268 |
+
assert unchanged(ceiling, k*x)
|
269 |
+
|
270 |
+
assert ceiling(k) == k
|
271 |
+
assert ceiling(2*k) == 2*k
|
272 |
+
assert ceiling(k*n) == k*n
|
273 |
+
|
274 |
+
assert unchanged(ceiling, k/2)
|
275 |
+
|
276 |
+
assert unchanged(ceiling, x + y)
|
277 |
+
|
278 |
+
assert ceiling(x + 3) == ceiling(x) + 3
|
279 |
+
assert ceiling(x + k) == ceiling(x) + k
|
280 |
+
|
281 |
+
assert ceiling(y + 3) == ceiling(y) + 3
|
282 |
+
assert ceiling(y + k) == ceiling(y) + k
|
283 |
+
|
284 |
+
assert ceiling(3 + pi + y*I) == 7 + ceiling(y)*I
|
285 |
+
|
286 |
+
assert ceiling(k + n) == k + n
|
287 |
+
|
288 |
+
assert unchanged(ceiling, x*I)
|
289 |
+
assert ceiling(k*I) == k*I
|
290 |
+
|
291 |
+
assert ceiling(Rational(23, 10) - E*I) == 3 - 2*I
|
292 |
+
|
293 |
+
assert ceiling(sin(1)) == 1
|
294 |
+
assert ceiling(sin(-1)) == 0
|
295 |
+
|
296 |
+
assert ceiling(exp(2)) == 8
|
297 |
+
|
298 |
+
assert ceiling(-log(8)/log(2)) != -2
|
299 |
+
assert int(ceiling(-log(8)/log(2)).evalf(chop=True)) == -3
|
300 |
+
|
301 |
+
assert ceiling(factorial(50)/exp(1)) == \
|
302 |
+
11188719610782480504630258070757734324011354208865721592720336801
|
303 |
+
|
304 |
+
assert (ceiling(y) >= y) == True
|
305 |
+
assert (ceiling(y) > y) == False
|
306 |
+
assert (ceiling(y) < y) == False
|
307 |
+
assert (ceiling(y) <= y) == False
|
308 |
+
assert (ceiling(x) >= x).is_Relational # x could be non-real
|
309 |
+
assert (ceiling(x) < x).is_Relational
|
310 |
+
assert (ceiling(x) >= y).is_Relational # arg is not same as rhs
|
311 |
+
assert (ceiling(x) < y).is_Relational
|
312 |
+
assert (ceiling(y) >= -oo) == True
|
313 |
+
assert (ceiling(y) > -oo) == True
|
314 |
+
assert (ceiling(y) <= oo) == True
|
315 |
+
assert (ceiling(y) < oo) == True
|
316 |
+
|
317 |
+
assert ceiling(y).rewrite(floor) == -floor(-y)
|
318 |
+
assert ceiling(y).rewrite(frac) == y + frac(-y)
|
319 |
+
assert ceiling(y).rewrite(floor).subs(y, -pi) == -floor(pi)
|
320 |
+
assert ceiling(y).rewrite(floor).subs(y, E) == -floor(-E)
|
321 |
+
assert ceiling(y).rewrite(frac).subs(y, pi) == ceiling(pi)
|
322 |
+
assert ceiling(y).rewrite(frac).subs(y, -E) == ceiling(-E)
|
323 |
+
|
324 |
+
assert Eq(ceiling(y), y + frac(-y))
|
325 |
+
assert Eq(ceiling(y), -floor(-y))
|
326 |
+
|
327 |
+
neg = Symbol('neg', negative=True)
|
328 |
+
nn = Symbol('nn', nonnegative=True)
|
329 |
+
pos = Symbol('pos', positive=True)
|
330 |
+
np = Symbol('np', nonpositive=True)
|
331 |
+
|
332 |
+
assert (ceiling(neg) <= 0) == True
|
333 |
+
assert (ceiling(neg) < 0) == (neg <= -1)
|
334 |
+
assert (ceiling(neg) > 0) == False
|
335 |
+
assert (ceiling(neg) >= 0) == (neg > -1)
|
336 |
+
assert (ceiling(neg) > -3) == (neg > -3)
|
337 |
+
assert (ceiling(neg) <= 10) == (neg <= 10)
|
338 |
+
|
339 |
+
assert (ceiling(nn) < 0) == False
|
340 |
+
assert (ceiling(nn) >= 0) == True
|
341 |
+
|
342 |
+
assert (ceiling(pos) < 0) == False
|
343 |
+
assert (ceiling(pos) <= 0) == False
|
344 |
+
assert (ceiling(pos) > 0) == True
|
345 |
+
assert (ceiling(pos) >= 0) == True
|
346 |
+
assert (ceiling(pos) >= 1) == True
|
347 |
+
assert (ceiling(pos) > 5) == (pos > 5)
|
348 |
+
|
349 |
+
assert (ceiling(np) <= 0) == True
|
350 |
+
assert (ceiling(np) > 0) == False
|
351 |
+
|
352 |
+
assert ceiling(neg).is_positive == False
|
353 |
+
assert ceiling(neg).is_nonpositive == True
|
354 |
+
assert ceiling(nn).is_positive is None
|
355 |
+
assert ceiling(nn).is_nonpositive is None
|
356 |
+
assert ceiling(pos).is_positive == True
|
357 |
+
assert ceiling(pos).is_nonpositive == False
|
358 |
+
assert ceiling(np).is_positive == False
|
359 |
+
assert ceiling(np).is_nonpositive == True
|
360 |
+
|
361 |
+
assert (ceiling(7, evaluate=False) >= 7) == True
|
362 |
+
assert (ceiling(7, evaluate=False) > 7) == False
|
363 |
+
assert (ceiling(7, evaluate=False) <= 7) == True
|
364 |
+
assert (ceiling(7, evaluate=False) < 7) == False
|
365 |
+
|
366 |
+
assert (ceiling(7, evaluate=False) >= 6) == True
|
367 |
+
assert (ceiling(7, evaluate=False) > 6) == True
|
368 |
+
assert (ceiling(7, evaluate=False) <= 6) == False
|
369 |
+
assert (ceiling(7, evaluate=False) < 6) == False
|
370 |
+
|
371 |
+
assert (ceiling(7, evaluate=False) >= 8) == False
|
372 |
+
assert (ceiling(7, evaluate=False) > 8) == False
|
373 |
+
assert (ceiling(7, evaluate=False) <= 8) == True
|
374 |
+
assert (ceiling(7, evaluate=False) < 8) == True
|
375 |
+
|
376 |
+
assert (ceiling(x) <= 5.5) == Le(ceiling(x), 5.5, evaluate=False)
|
377 |
+
assert (ceiling(x) >= -3.2) == Ge(ceiling(x), -3.2, evaluate=False)
|
378 |
+
assert (ceiling(x) < 2.9) == Lt(ceiling(x), 2.9, evaluate=False)
|
379 |
+
assert (ceiling(x) > -1.7) == Gt(ceiling(x), -1.7, evaluate=False)
|
380 |
+
|
381 |
+
assert (ceiling(y) <= 5.5) == (y <= 5)
|
382 |
+
assert (ceiling(y) >= -3.2) == (y > -4)
|
383 |
+
assert (ceiling(y) < 2.9) == (y <= 2)
|
384 |
+
assert (ceiling(y) > -1.7) == (y > -2)
|
385 |
+
|
386 |
+
assert (ceiling(y) <= n) == (y <= n)
|
387 |
+
assert (ceiling(y) >= n) == (y > n - 1)
|
388 |
+
assert (ceiling(y) < n) == (y <= n - 1)
|
389 |
+
assert (ceiling(y) > n) == (y > n)
|
390 |
+
|
391 |
+
|
392 |
+
def test_frac():
|
393 |
+
assert isinstance(frac(x), frac)
|
394 |
+
assert frac(oo) == AccumBounds(0, 1)
|
395 |
+
assert frac(-oo) == AccumBounds(0, 1)
|
396 |
+
assert frac(zoo) is nan
|
397 |
+
|
398 |
+
assert frac(n) == 0
|
399 |
+
assert frac(nan) is nan
|
400 |
+
assert frac(Rational(4, 3)) == Rational(1, 3)
|
401 |
+
assert frac(-Rational(4, 3)) == Rational(2, 3)
|
402 |
+
assert frac(Rational(-4, 3)) == Rational(2, 3)
|
403 |
+
|
404 |
+
r = Symbol('r', real=True)
|
405 |
+
assert frac(I*r) == I*frac(r)
|
406 |
+
assert frac(1 + I*r) == I*frac(r)
|
407 |
+
assert frac(0.5 + I*r) == 0.5 + I*frac(r)
|
408 |
+
assert frac(n + I*r) == I*frac(r)
|
409 |
+
assert frac(n + I*k) == 0
|
410 |
+
assert unchanged(frac, x + I*x)
|
411 |
+
assert frac(x + I*n) == frac(x)
|
412 |
+
|
413 |
+
assert frac(x).rewrite(floor) == x - floor(x)
|
414 |
+
assert frac(x).rewrite(ceiling) == x + ceiling(-x)
|
415 |
+
assert frac(y).rewrite(floor).subs(y, pi) == frac(pi)
|
416 |
+
assert frac(y).rewrite(floor).subs(y, -E) == frac(-E)
|
417 |
+
assert frac(y).rewrite(ceiling).subs(y, -pi) == frac(-pi)
|
418 |
+
assert frac(y).rewrite(ceiling).subs(y, E) == frac(E)
|
419 |
+
|
420 |
+
assert Eq(frac(y), y - floor(y))
|
421 |
+
assert Eq(frac(y), y + ceiling(-y))
|
422 |
+
|
423 |
+
r = Symbol('r', real=True)
|
424 |
+
p_i = Symbol('p_i', integer=True, positive=True)
|
425 |
+
n_i = Symbol('p_i', integer=True, negative=True)
|
426 |
+
np_i = Symbol('np_i', integer=True, nonpositive=True)
|
427 |
+
nn_i = Symbol('nn_i', integer=True, nonnegative=True)
|
428 |
+
p_r = Symbol('p_r', positive=True)
|
429 |
+
n_r = Symbol('n_r', negative=True)
|
430 |
+
np_r = Symbol('np_r', real=True, nonpositive=True)
|
431 |
+
nn_r = Symbol('nn_r', real=True, nonnegative=True)
|
432 |
+
|
433 |
+
# Real frac argument, integer rhs
|
434 |
+
assert frac(r) <= p_i
|
435 |
+
assert not frac(r) <= n_i
|
436 |
+
assert (frac(r) <= np_i).has(Le)
|
437 |
+
assert (frac(r) <= nn_i).has(Le)
|
438 |
+
assert frac(r) < p_i
|
439 |
+
assert not frac(r) < n_i
|
440 |
+
assert not frac(r) < np_i
|
441 |
+
assert (frac(r) < nn_i).has(Lt)
|
442 |
+
assert not frac(r) >= p_i
|
443 |
+
assert frac(r) >= n_i
|
444 |
+
assert frac(r) >= np_i
|
445 |
+
assert (frac(r) >= nn_i).has(Ge)
|
446 |
+
assert not frac(r) > p_i
|
447 |
+
assert frac(r) > n_i
|
448 |
+
assert (frac(r) > np_i).has(Gt)
|
449 |
+
assert (frac(r) > nn_i).has(Gt)
|
450 |
+
|
451 |
+
assert not Eq(frac(r), p_i)
|
452 |
+
assert not Eq(frac(r), n_i)
|
453 |
+
assert Eq(frac(r), np_i).has(Eq)
|
454 |
+
assert Eq(frac(r), nn_i).has(Eq)
|
455 |
+
|
456 |
+
assert Ne(frac(r), p_i)
|
457 |
+
assert Ne(frac(r), n_i)
|
458 |
+
assert Ne(frac(r), np_i).has(Ne)
|
459 |
+
assert Ne(frac(r), nn_i).has(Ne)
|
460 |
+
|
461 |
+
|
462 |
+
# Real frac argument, real rhs
|
463 |
+
assert (frac(r) <= p_r).has(Le)
|
464 |
+
assert not frac(r) <= n_r
|
465 |
+
assert (frac(r) <= np_r).has(Le)
|
466 |
+
assert (frac(r) <= nn_r).has(Le)
|
467 |
+
assert (frac(r) < p_r).has(Lt)
|
468 |
+
assert not frac(r) < n_r
|
469 |
+
assert not frac(r) < np_r
|
470 |
+
assert (frac(r) < nn_r).has(Lt)
|
471 |
+
assert (frac(r) >= p_r).has(Ge)
|
472 |
+
assert frac(r) >= n_r
|
473 |
+
assert frac(r) >= np_r
|
474 |
+
assert (frac(r) >= nn_r).has(Ge)
|
475 |
+
assert (frac(r) > p_r).has(Gt)
|
476 |
+
assert frac(r) > n_r
|
477 |
+
assert (frac(r) > np_r).has(Gt)
|
478 |
+
assert (frac(r) > nn_r).has(Gt)
|
479 |
+
|
480 |
+
assert not Eq(frac(r), n_r)
|
481 |
+
assert Eq(frac(r), p_r).has(Eq)
|
482 |
+
assert Eq(frac(r), np_r).has(Eq)
|
483 |
+
assert Eq(frac(r), nn_r).has(Eq)
|
484 |
+
|
485 |
+
assert Ne(frac(r), p_r).has(Ne)
|
486 |
+
assert Ne(frac(r), n_r)
|
487 |
+
assert Ne(frac(r), np_r).has(Ne)
|
488 |
+
assert Ne(frac(r), nn_r).has(Ne)
|
489 |
+
|
490 |
+
# Real frac argument, +/- oo rhs
|
491 |
+
assert frac(r) < oo
|
492 |
+
assert frac(r) <= oo
|
493 |
+
assert not frac(r) > oo
|
494 |
+
assert not frac(r) >= oo
|
495 |
+
|
496 |
+
assert not frac(r) < -oo
|
497 |
+
assert not frac(r) <= -oo
|
498 |
+
assert frac(r) > -oo
|
499 |
+
assert frac(r) >= -oo
|
500 |
+
|
501 |
+
assert frac(r) < 1
|
502 |
+
assert frac(r) <= 1
|
503 |
+
assert not frac(r) > 1
|
504 |
+
assert not frac(r) >= 1
|
505 |
+
|
506 |
+
assert not frac(r) < 0
|
507 |
+
assert (frac(r) <= 0).has(Le)
|
508 |
+
assert (frac(r) > 0).has(Gt)
|
509 |
+
assert frac(r) >= 0
|
510 |
+
|
511 |
+
# Some test for numbers
|
512 |
+
assert frac(r) <= sqrt(2)
|
513 |
+
assert (frac(r) <= sqrt(3) - sqrt(2)).has(Le)
|
514 |
+
assert not frac(r) <= sqrt(2) - sqrt(3)
|
515 |
+
assert not frac(r) >= sqrt(2)
|
516 |
+
assert (frac(r) >= sqrt(3) - sqrt(2)).has(Ge)
|
517 |
+
assert frac(r) >= sqrt(2) - sqrt(3)
|
518 |
+
|
519 |
+
assert not Eq(frac(r), sqrt(2))
|
520 |
+
assert Eq(frac(r), sqrt(3) - sqrt(2)).has(Eq)
|
521 |
+
assert not Eq(frac(r), sqrt(2) - sqrt(3))
|
522 |
+
assert Ne(frac(r), sqrt(2))
|
523 |
+
assert Ne(frac(r), sqrt(3) - sqrt(2)).has(Ne)
|
524 |
+
assert Ne(frac(r), sqrt(2) - sqrt(3))
|
525 |
+
|
526 |
+
assert frac(p_i, evaluate=False).is_zero
|
527 |
+
assert frac(p_i, evaluate=False).is_finite
|
528 |
+
assert frac(p_i, evaluate=False).is_integer
|
529 |
+
assert frac(p_i, evaluate=False).is_real
|
530 |
+
assert frac(r).is_finite
|
531 |
+
assert frac(r).is_real
|
532 |
+
assert frac(r).is_zero is None
|
533 |
+
assert frac(r).is_integer is None
|
534 |
+
|
535 |
+
assert frac(oo).is_finite
|
536 |
+
assert frac(oo).is_real
|
537 |
+
|
538 |
+
|
539 |
+
def test_series():
|
540 |
+
x, y = symbols('x,y')
|
541 |
+
assert floor(x).nseries(x, y, 100) == floor(y)
|
542 |
+
assert ceiling(x).nseries(x, y, 100) == ceiling(y)
|
543 |
+
assert floor(x).nseries(x, pi, 100) == 3
|
544 |
+
assert ceiling(x).nseries(x, pi, 100) == 4
|
545 |
+
assert floor(x).nseries(x, 0, 100) == 0
|
546 |
+
assert ceiling(x).nseries(x, 0, 100) == 1
|
547 |
+
assert floor(-x).nseries(x, 0, 100) == -1
|
548 |
+
assert ceiling(-x).nseries(x, 0, 100) == 0
|
549 |
+
|
550 |
+
|
551 |
+
def test_issue_14355():
|
552 |
+
# This test checks the leading term and series for the floor and ceil
|
553 |
+
# function when arg0 evaluates to S.NaN.
|
554 |
+
assert floor((x**3 + x)/(x**2 - x)).as_leading_term(x, cdir = 1) == -2
|
555 |
+
assert floor((x**3 + x)/(x**2 - x)).as_leading_term(x, cdir = -1) == -1
|
556 |
+
assert floor((cos(x) - 1)/x).as_leading_term(x, cdir = 1) == -1
|
557 |
+
assert floor((cos(x) - 1)/x).as_leading_term(x, cdir = -1) == 0
|
558 |
+
assert floor(sin(x)/x).as_leading_term(x, cdir = 1) == 0
|
559 |
+
assert floor(sin(x)/x).as_leading_term(x, cdir = -1) == 0
|
560 |
+
assert floor(-tan(x)/x).as_leading_term(x, cdir = 1) == -2
|
561 |
+
assert floor(-tan(x)/x).as_leading_term(x, cdir = -1) == -2
|
562 |
+
assert floor(sin(x)/x/3).as_leading_term(x, cdir = 1) == 0
|
563 |
+
assert floor(sin(x)/x/3).as_leading_term(x, cdir = -1) == 0
|
564 |
+
assert ceiling((x**3 + x)/(x**2 - x)).as_leading_term(x, cdir = 1) == -1
|
565 |
+
assert ceiling((x**3 + x)/(x**2 - x)).as_leading_term(x, cdir = -1) == 0
|
566 |
+
assert ceiling((cos(x) - 1)/x).as_leading_term(x, cdir = 1) == 0
|
567 |
+
assert ceiling((cos(x) - 1)/x).as_leading_term(x, cdir = -1) == 1
|
568 |
+
assert ceiling(sin(x)/x).as_leading_term(x, cdir = 1) == 1
|
569 |
+
assert ceiling(sin(x)/x).as_leading_term(x, cdir = -1) == 1
|
570 |
+
assert ceiling(-tan(x)/x).as_leading_term(x, cdir = 1) == -1
|
571 |
+
assert ceiling(-tan(x)/x).as_leading_term(x, cdir = 1) == -1
|
572 |
+
assert ceiling(sin(x)/x/3).as_leading_term(x, cdir = 1) == 1
|
573 |
+
assert ceiling(sin(x)/x/3).as_leading_term(x, cdir = -1) == 1
|
574 |
+
# test for series
|
575 |
+
assert floor(sin(x)/x).series(x, 0, 100, cdir = 1) == 0
|
576 |
+
assert floor(sin(x)/x).series(x, 0, 100, cdir = 1) == 0
|
577 |
+
assert floor((x**3 + x)/(x**2 - x)).series(x, 0, 100, cdir = 1) == -2
|
578 |
+
assert floor((x**3 + x)/(x**2 - x)).series(x, 0, 100, cdir = -1) == -1
|
579 |
+
assert ceiling(sin(x)/x).series(x, 0, 100, cdir = 1) == 1
|
580 |
+
assert ceiling(sin(x)/x).series(x, 0, 100, cdir = -1) == 1
|
581 |
+
assert ceiling((x**3 + x)/(x**2 - x)).series(x, 0, 100, cdir = 1) == -1
|
582 |
+
assert ceiling((x**3 + x)/(x**2 - x)).series(x, 0, 100, cdir = -1) == 0
|
583 |
+
|
584 |
+
|
585 |
+
def test_frac_leading_term():
|
586 |
+
assert frac(x).as_leading_term(x) == x
|
587 |
+
assert frac(x).as_leading_term(x, cdir = 1) == x
|
588 |
+
assert frac(x).as_leading_term(x, cdir = -1) == 1
|
589 |
+
assert frac(x + S.Half).as_leading_term(x, cdir = 1) == S.Half
|
590 |
+
assert frac(x + S.Half).as_leading_term(x, cdir = -1) == S.Half
|
591 |
+
assert frac(-2*x + 1).as_leading_term(x, cdir = 1) == S.One
|
592 |
+
assert frac(-2*x + 1).as_leading_term(x, cdir = -1) == -2*x
|
593 |
+
assert frac(sin(x) + 5).as_leading_term(x, cdir = 1) == x
|
594 |
+
assert frac(sin(x) + 5).as_leading_term(x, cdir = -1) == S.One
|
595 |
+
assert frac(sin(x**2) + 5).as_leading_term(x, cdir = 1) == x**2
|
596 |
+
assert frac(sin(x**2) + 5).as_leading_term(x, cdir = -1) == x**2
|
597 |
+
|
598 |
+
|
599 |
+
@XFAIL
|
600 |
+
def test_issue_4149():
|
601 |
+
assert floor(3 + pi*I + y*I) == 3 + floor(pi + y)*I
|
602 |
+
assert floor(3*I + pi*I + y*I) == floor(3 + pi + y)*I
|
603 |
+
assert floor(3 + E + pi*I + y*I) == 5 + floor(pi + y)*I
|
604 |
+
|
605 |
+
|
606 |
+
def test_issue_21651():
|
607 |
+
k = Symbol('k', positive=True, integer=True)
|
608 |
+
exp = 2*2**(-k)
|
609 |
+
assert isinstance(floor(exp), floor)
|
610 |
+
|
611 |
+
|
612 |
+
def test_issue_11207():
|
613 |
+
assert floor(floor(x)) == floor(x)
|
614 |
+
assert floor(ceiling(x)) == ceiling(x)
|
615 |
+
assert ceiling(floor(x)) == floor(x)
|
616 |
+
assert ceiling(ceiling(x)) == ceiling(x)
|
617 |
+
|
618 |
+
|
619 |
+
def test_nested_floor_ceiling():
|
620 |
+
assert floor(-floor(ceiling(x**3)/y)) == -floor(ceiling(x**3)/y)
|
621 |
+
assert ceiling(-floor(ceiling(x**3)/y)) == -floor(ceiling(x**3)/y)
|
622 |
+
assert floor(ceiling(-floor(x**Rational(7, 2)/y))) == -floor(x**Rational(7, 2)/y)
|
623 |
+
assert -ceiling(-ceiling(floor(x)/y)) == ceiling(floor(x)/y)
|
624 |
+
|
625 |
+
def test_issue_18689():
|
626 |
+
assert floor(floor(floor(x)) + 3) == floor(x) + 3
|
627 |
+
assert ceiling(ceiling(ceiling(x)) + 1) == ceiling(x) + 1
|
628 |
+
assert ceiling(ceiling(floor(x)) + 3) == floor(x) + 3
|
629 |
+
|
630 |
+
def test_issue_18421():
|
631 |
+
assert floor(float(0)) is S.Zero
|
632 |
+
assert ceiling(float(0)) is S.Zero
|
venv/lib/python3.10/site-packages/sympy/functions/special/__init__.py
ADDED
@@ -0,0 +1 @@
|
|
|
|
|
1 |
+
# Stub __init__.py for the sympy.functions.special package
|
venv/lib/python3.10/site-packages/sympy/functions/special/__pycache__/__init__.cpython-310.pyc
ADDED
Binary file (191 Bytes). View file
|
|
venv/lib/python3.10/site-packages/sympy/functions/special/__pycache__/bessel.cpython-310.pyc
ADDED
Binary file (58.7 kB). View file
|
|
venv/lib/python3.10/site-packages/sympy/functions/special/__pycache__/beta_functions.cpython-310.pyc
ADDED
Binary file (13.2 kB). View file
|
|
venv/lib/python3.10/site-packages/sympy/functions/special/__pycache__/bsplines.cpython-310.pyc
ADDED
Binary file (10.5 kB). View file
|
|
venv/lib/python3.10/site-packages/sympy/functions/special/__pycache__/delta_functions.cpython-310.pyc
ADDED
Binary file (18.6 kB). View file
|
|
venv/lib/python3.10/site-packages/sympy/functions/special/__pycache__/elliptic_integrals.cpython-310.pyc
ADDED
Binary file (14.5 kB). View file
|
|
venv/lib/python3.10/site-packages/sympy/functions/special/__pycache__/error_functions.cpython-310.pyc
ADDED
Binary file (78.9 kB). View file
|
|
venv/lib/python3.10/site-packages/sympy/functions/special/__pycache__/gamma_functions.cpython-310.pyc
ADDED
Binary file (41.3 kB). View file
|
|
venv/lib/python3.10/site-packages/sympy/functions/special/__pycache__/hyper.cpython-310.pyc
ADDED
Binary file (40.3 kB). View file
|
|
venv/lib/python3.10/site-packages/sympy/functions/special/__pycache__/mathieu_functions.cpython-310.pyc
ADDED
Binary file (7.08 kB). View file
|
|
venv/lib/python3.10/site-packages/sympy/functions/special/__pycache__/polynomials.cpython-310.pyc
ADDED
Binary file (39.4 kB). View file
|
|
venv/lib/python3.10/site-packages/sympy/functions/special/__pycache__/singularity_functions.cpython-310.pyc
ADDED
Binary file (7.95 kB). View file
|
|
venv/lib/python3.10/site-packages/sympy/functions/special/__pycache__/spherical_harmonics.cpython-310.pyc
ADDED
Binary file (10.9 kB). View file
|
|
venv/lib/python3.10/site-packages/sympy/functions/special/__pycache__/tensor_functions.cpython-310.pyc
ADDED
Binary file (12.4 kB). View file
|
|
venv/lib/python3.10/site-packages/sympy/functions/special/__pycache__/zeta_functions.cpython-310.pyc
ADDED
Binary file (23.1 kB). View file
|
|
venv/lib/python3.10/site-packages/sympy/functions/special/benchmarks/__init__.py
ADDED
File without changes
|
venv/lib/python3.10/site-packages/sympy/functions/special/benchmarks/__pycache__/bench_special.cpython-310.pyc
ADDED
Binary file (491 Bytes). View file
|
|
venv/lib/python3.10/site-packages/sympy/functions/special/benchmarks/bench_special.py
ADDED
@@ -0,0 +1,8 @@
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
1 |
+
from sympy.core.symbol import symbols
|
2 |
+
from sympy.functions.special.spherical_harmonics import Ynm
|
3 |
+
|
4 |
+
x, y = symbols('x,y')
|
5 |
+
|
6 |
+
|
7 |
+
def timeit_Ynm_xy():
|
8 |
+
Ynm(1, 1, x, y)
|
venv/lib/python3.10/site-packages/sympy/functions/special/bessel.py
ADDED
@@ -0,0 +1,2089 @@
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|
1 |
+
from functools import wraps
|
2 |
+
|
3 |
+
from sympy.core import S
|
4 |
+
from sympy.core.add import Add
|
5 |
+
from sympy.core.cache import cacheit
|
6 |
+
from sympy.core.expr import Expr
|
7 |
+
from sympy.core.function import Function, ArgumentIndexError, _mexpand
|
8 |
+
from sympy.core.logic import fuzzy_or, fuzzy_not
|
9 |
+
from sympy.core.numbers import Rational, pi, I
|
10 |
+
from sympy.core.power import Pow
|
11 |
+
from sympy.core.symbol import Dummy, Wild
|
12 |
+
from sympy.core.sympify import sympify
|
13 |
+
from sympy.functions.combinatorial.factorials import factorial
|
14 |
+
from sympy.functions.elementary.trigonometric import sin, cos, csc, cot
|
15 |
+
from sympy.functions.elementary.integers import ceiling
|
16 |
+
from sympy.functions.elementary.exponential import exp, log
|
17 |
+
from sympy.functions.elementary.miscellaneous import cbrt, sqrt, root
|
18 |
+
from sympy.functions.elementary.complexes import (Abs, re, im, polar_lift, unpolarify)
|
19 |
+
from sympy.functions.special.gamma_functions import gamma, digamma, uppergamma
|
20 |
+
from sympy.functions.special.hyper import hyper
|
21 |
+
from sympy.polys.orthopolys import spherical_bessel_fn
|
22 |
+
|
23 |
+
from mpmath import mp, workprec
|
24 |
+
|
25 |
+
# TODO
|
26 |
+
# o Scorer functions G1 and G2
|
27 |
+
# o Asymptotic expansions
|
28 |
+
# These are possible, e.g. for fixed order, but since the bessel type
|
29 |
+
# functions are oscillatory they are not actually tractable at
|
30 |
+
# infinity, so this is not particularly useful right now.
|
31 |
+
# o Nicer series expansions.
|
32 |
+
# o More rewriting.
|
33 |
+
# o Add solvers to ode.py (or rather add solvers for the hypergeometric equation).
|
34 |
+
|
35 |
+
|
36 |
+
class BesselBase(Function):
|
37 |
+
"""
|
38 |
+
Abstract base class for Bessel-type functions.
|
39 |
+
|
40 |
+
This class is meant to reduce code duplication.
|
41 |
+
All Bessel-type functions can 1) be differentiated, with the derivatives
|
42 |
+
expressed in terms of similar functions, and 2) be rewritten in terms
|
43 |
+
of other Bessel-type functions.
|
44 |
+
|
45 |
+
Here, Bessel-type functions are assumed to have one complex parameter.
|
46 |
+
|
47 |
+
To use this base class, define class attributes ``_a`` and ``_b`` such that
|
48 |
+
``2*F_n' = -_a*F_{n+1} + b*F_{n-1}``.
|
49 |
+
|
50 |
+
"""
|
51 |
+
|
52 |
+
@property
|
53 |
+
def order(self):
|
54 |
+
""" The order of the Bessel-type function. """
|
55 |
+
return self.args[0]
|
56 |
+
|
57 |
+
@property
|
58 |
+
def argument(self):
|
59 |
+
""" The argument of the Bessel-type function. """
|
60 |
+
return self.args[1]
|
61 |
+
|
62 |
+
@classmethod
|
63 |
+
def eval(cls, nu, z):
|
64 |
+
return
|
65 |
+
|
66 |
+
def fdiff(self, argindex=2):
|
67 |
+
if argindex != 2:
|
68 |
+
raise ArgumentIndexError(self, argindex)
|
69 |
+
return (self._b/2 * self.__class__(self.order - 1, self.argument) -
|
70 |
+
self._a/2 * self.__class__(self.order + 1, self.argument))
|
71 |
+
|
72 |
+
def _eval_conjugate(self):
|
73 |
+
z = self.argument
|
74 |
+
if z.is_extended_negative is False:
|
75 |
+
return self.__class__(self.order.conjugate(), z.conjugate())
|
76 |
+
|
77 |
+
def _eval_is_meromorphic(self, x, a):
|
78 |
+
nu, z = self.order, self.argument
|
79 |
+
|
80 |
+
if nu.has(x):
|
81 |
+
return False
|
82 |
+
if not z._eval_is_meromorphic(x, a):
|
83 |
+
return None
|
84 |
+
z0 = z.subs(x, a)
|
85 |
+
if nu.is_integer:
|
86 |
+
if isinstance(self, (besselj, besseli, hn1, hn2, jn, yn)) or not nu.is_zero:
|
87 |
+
return fuzzy_not(z0.is_infinite)
|
88 |
+
return fuzzy_not(fuzzy_or([z0.is_zero, z0.is_infinite]))
|
89 |
+
|
90 |
+
def _eval_expand_func(self, **hints):
|
91 |
+
nu, z, f = self.order, self.argument, self.__class__
|
92 |
+
if nu.is_real:
|
93 |
+
if (nu - 1).is_positive:
|
94 |
+
return (-self._a*self._b*f(nu - 2, z)._eval_expand_func() +
|
95 |
+
2*self._a*(nu - 1)*f(nu - 1, z)._eval_expand_func()/z)
|
96 |
+
elif (nu + 1).is_negative:
|
97 |
+
return (2*self._b*(nu + 1)*f(nu + 1, z)._eval_expand_func()/z -
|
98 |
+
self._a*self._b*f(nu + 2, z)._eval_expand_func())
|
99 |
+
return self
|
100 |
+
|
101 |
+
def _eval_simplify(self, **kwargs):
|
102 |
+
from sympy.simplify.simplify import besselsimp
|
103 |
+
return besselsimp(self)
|
104 |
+
|
105 |
+
|
106 |
+
class besselj(BesselBase):
|
107 |
+
r"""
|
108 |
+
Bessel function of the first kind.
|
109 |
+
|
110 |
+
Explanation
|
111 |
+
===========
|
112 |
+
|
113 |
+
The Bessel $J$ function of order $\nu$ is defined to be the function
|
114 |
+
satisfying Bessel's differential equation
|
115 |
+
|
116 |
+
.. math ::
|
117 |
+
z^2 \frac{\mathrm{d}^2 w}{\mathrm{d}z^2}
|
118 |
+
+ z \frac{\mathrm{d}w}{\mathrm{d}z} + (z^2 - \nu^2) w = 0,
|
119 |
+
|
120 |
+
with Laurent expansion
|
121 |
+
|
122 |
+
.. math ::
|
123 |
+
J_\nu(z) = z^\nu \left(\frac{1}{\Gamma(\nu + 1) 2^\nu} + O(z^2) \right),
|
124 |
+
|
125 |
+
if $\nu$ is not a negative integer. If $\nu=-n \in \mathbb{Z}_{<0}$
|
126 |
+
*is* a negative integer, then the definition is
|
127 |
+
|
128 |
+
.. math ::
|
129 |
+
J_{-n}(z) = (-1)^n J_n(z).
|
130 |
+
|
131 |
+
Examples
|
132 |
+
========
|
133 |
+
|
134 |
+
Create a Bessel function object:
|
135 |
+
|
136 |
+
>>> from sympy import besselj, jn
|
137 |
+
>>> from sympy.abc import z, n
|
138 |
+
>>> b = besselj(n, z)
|
139 |
+
|
140 |
+
Differentiate it:
|
141 |
+
|
142 |
+
>>> b.diff(z)
|
143 |
+
besselj(n - 1, z)/2 - besselj(n + 1, z)/2
|
144 |
+
|
145 |
+
Rewrite in terms of spherical Bessel functions:
|
146 |
+
|
147 |
+
>>> b.rewrite(jn)
|
148 |
+
sqrt(2)*sqrt(z)*jn(n - 1/2, z)/sqrt(pi)
|
149 |
+
|
150 |
+
Access the parameter and argument:
|
151 |
+
|
152 |
+
>>> b.order
|
153 |
+
n
|
154 |
+
>>> b.argument
|
155 |
+
z
|
156 |
+
|
157 |
+
See Also
|
158 |
+
========
|
159 |
+
|
160 |
+
bessely, besseli, besselk
|
161 |
+
|
162 |
+
References
|
163 |
+
==========
|
164 |
+
|
165 |
+
.. [1] Abramowitz, Milton; Stegun, Irene A., eds. (1965), "Chapter 9",
|
166 |
+
Handbook of Mathematical Functions with Formulas, Graphs, and
|
167 |
+
Mathematical Tables
|
168 |
+
.. [2] Luke, Y. L. (1969), The Special Functions and Their
|
169 |
+
Approximations, Volume 1
|
170 |
+
.. [3] https://en.wikipedia.org/wiki/Bessel_function
|
171 |
+
.. [4] https://functions.wolfram.com/Bessel-TypeFunctions/BesselJ/
|
172 |
+
|
173 |
+
"""
|
174 |
+
|
175 |
+
_a = S.One
|
176 |
+
_b = S.One
|
177 |
+
|
178 |
+
@classmethod
|
179 |
+
def eval(cls, nu, z):
|
180 |
+
if z.is_zero:
|
181 |
+
if nu.is_zero:
|
182 |
+
return S.One
|
183 |
+
elif (nu.is_integer and nu.is_zero is False) or re(nu).is_positive:
|
184 |
+
return S.Zero
|
185 |
+
elif re(nu).is_negative and not (nu.is_integer is True):
|
186 |
+
return S.ComplexInfinity
|
187 |
+
elif nu.is_imaginary:
|
188 |
+
return S.NaN
|
189 |
+
if z in (S.Infinity, S.NegativeInfinity):
|
190 |
+
return S.Zero
|
191 |
+
|
192 |
+
if z.could_extract_minus_sign():
|
193 |
+
return (z)**nu*(-z)**(-nu)*besselj(nu, -z)
|
194 |
+
if nu.is_integer:
|
195 |
+
if nu.could_extract_minus_sign():
|
196 |
+
return S.NegativeOne**(-nu)*besselj(-nu, z)
|
197 |
+
newz = z.extract_multiplicatively(I)
|
198 |
+
if newz: # NOTE we don't want to change the function if z==0
|
199 |
+
return I**(nu)*besseli(nu, newz)
|
200 |
+
|
201 |
+
# branch handling:
|
202 |
+
if nu.is_integer:
|
203 |
+
newz = unpolarify(z)
|
204 |
+
if newz != z:
|
205 |
+
return besselj(nu, newz)
|
206 |
+
else:
|
207 |
+
newz, n = z.extract_branch_factor()
|
208 |
+
if n != 0:
|
209 |
+
return exp(2*n*pi*nu*I)*besselj(nu, newz)
|
210 |
+
nnu = unpolarify(nu)
|
211 |
+
if nu != nnu:
|
212 |
+
return besselj(nnu, z)
|
213 |
+
|
214 |
+
def _eval_rewrite_as_besseli(self, nu, z, **kwargs):
|
215 |
+
return exp(I*pi*nu/2)*besseli(nu, polar_lift(-I)*z)
|
216 |
+
|
217 |
+
def _eval_rewrite_as_bessely(self, nu, z, **kwargs):
|
218 |
+
if nu.is_integer is False:
|
219 |
+
return csc(pi*nu)*bessely(-nu, z) - cot(pi*nu)*bessely(nu, z)
|
220 |
+
|
221 |
+
def _eval_rewrite_as_jn(self, nu, z, **kwargs):
|
222 |
+
return sqrt(2*z/pi)*jn(nu - S.Half, self.argument)
|
223 |
+
|
224 |
+
def _eval_as_leading_term(self, x, logx=None, cdir=0):
|
225 |
+
nu, z = self.args
|
226 |
+
try:
|
227 |
+
arg = z.as_leading_term(x)
|
228 |
+
except NotImplementedError:
|
229 |
+
return self
|
230 |
+
c, e = arg.as_coeff_exponent(x)
|
231 |
+
|
232 |
+
if e.is_positive:
|
233 |
+
return arg**nu/(2**nu*gamma(nu + 1))
|
234 |
+
elif e.is_negative:
|
235 |
+
cdir = 1 if cdir == 0 else cdir
|
236 |
+
sign = c*cdir**e
|
237 |
+
if not sign.is_negative:
|
238 |
+
# Refer Abramowitz and Stegun 1965, p. 364 for more information on
|
239 |
+
# asymptotic approximation of besselj function.
|
240 |
+
return sqrt(2)*cos(z - pi*(2*nu + 1)/4)/sqrt(pi*z)
|
241 |
+
return self
|
242 |
+
|
243 |
+
return super(besselj, self)._eval_as_leading_term(x, logx, cdir)
|
244 |
+
|
245 |
+
def _eval_is_extended_real(self):
|
246 |
+
nu, z = self.args
|
247 |
+
if nu.is_integer and z.is_extended_real:
|
248 |
+
return True
|
249 |
+
|
250 |
+
def _eval_nseries(self, x, n, logx, cdir=0):
|
251 |
+
# Refer https://functions.wolfram.com/Bessel-TypeFunctions/BesselJ/06/01/04/01/01/0003/
|
252 |
+
# for more information on nseries expansion of besselj function.
|
253 |
+
from sympy.series.order import Order
|
254 |
+
nu, z = self.args
|
255 |
+
|
256 |
+
# In case of powers less than 1, number of terms need to be computed
|
257 |
+
# separately to avoid repeated callings of _eval_nseries with wrong n
|
258 |
+
try:
|
259 |
+
_, exp = z.leadterm(x)
|
260 |
+
except (ValueError, NotImplementedError):
|
261 |
+
return self
|
262 |
+
|
263 |
+
if exp.is_positive:
|
264 |
+
newn = ceiling(n/exp)
|
265 |
+
o = Order(x**n, x)
|
266 |
+
r = (z/2)._eval_nseries(x, n, logx, cdir).removeO()
|
267 |
+
if r is S.Zero:
|
268 |
+
return o
|
269 |
+
t = (_mexpand(r**2) + o).removeO()
|
270 |
+
|
271 |
+
term = r**nu/gamma(nu + 1)
|
272 |
+
s = [term]
|
273 |
+
for k in range(1, (newn + 1)//2):
|
274 |
+
term *= -t/(k*(nu + k))
|
275 |
+
term = (_mexpand(term) + o).removeO()
|
276 |
+
s.append(term)
|
277 |
+
return Add(*s) + o
|
278 |
+
|
279 |
+
return super(besselj, self)._eval_nseries(x, n, logx, cdir)
|
280 |
+
|
281 |
+
|
282 |
+
class bessely(BesselBase):
|
283 |
+
r"""
|
284 |
+
Bessel function of the second kind.
|
285 |
+
|
286 |
+
Explanation
|
287 |
+
===========
|
288 |
+
|
289 |
+
The Bessel $Y$ function of order $\nu$ is defined as
|
290 |
+
|
291 |
+
.. math ::
|
292 |
+
Y_\nu(z) = \lim_{\mu \to \nu} \frac{J_\mu(z) \cos(\pi \mu)
|
293 |
+
- J_{-\mu}(z)}{\sin(\pi \mu)},
|
294 |
+
|
295 |
+
where $J_\mu(z)$ is the Bessel function of the first kind.
|
296 |
+
|
297 |
+
It is a solution to Bessel's equation, and linearly independent from
|
298 |
+
$J_\nu$.
|
299 |
+
|
300 |
+
Examples
|
301 |
+
========
|
302 |
+
|
303 |
+
>>> from sympy import bessely, yn
|
304 |
+
>>> from sympy.abc import z, n
|
305 |
+
>>> b = bessely(n, z)
|
306 |
+
>>> b.diff(z)
|
307 |
+
bessely(n - 1, z)/2 - bessely(n + 1, z)/2
|
308 |
+
>>> b.rewrite(yn)
|
309 |
+
sqrt(2)*sqrt(z)*yn(n - 1/2, z)/sqrt(pi)
|
310 |
+
|
311 |
+
See Also
|
312 |
+
========
|
313 |
+
|
314 |
+
besselj, besseli, besselk
|
315 |
+
|
316 |
+
References
|
317 |
+
==========
|
318 |
+
|
319 |
+
.. [1] https://functions.wolfram.com/Bessel-TypeFunctions/BesselY/
|
320 |
+
|
321 |
+
"""
|
322 |
+
|
323 |
+
_a = S.One
|
324 |
+
_b = S.One
|
325 |
+
|
326 |
+
@classmethod
|
327 |
+
def eval(cls, nu, z):
|
328 |
+
if z.is_zero:
|
329 |
+
if nu.is_zero:
|
330 |
+
return S.NegativeInfinity
|
331 |
+
elif re(nu).is_zero is False:
|
332 |
+
return S.ComplexInfinity
|
333 |
+
elif re(nu).is_zero:
|
334 |
+
return S.NaN
|
335 |
+
if z in (S.Infinity, S.NegativeInfinity):
|
336 |
+
return S.Zero
|
337 |
+
if z == I*S.Infinity:
|
338 |
+
return exp(I*pi*(nu + 1)/2) * S.Infinity
|
339 |
+
if z == I*S.NegativeInfinity:
|
340 |
+
return exp(-I*pi*(nu + 1)/2) * S.Infinity
|
341 |
+
|
342 |
+
if nu.is_integer:
|
343 |
+
if nu.could_extract_minus_sign():
|
344 |
+
return S.NegativeOne**(-nu)*bessely(-nu, z)
|
345 |
+
|
346 |
+
def _eval_rewrite_as_besselj(self, nu, z, **kwargs):
|
347 |
+
if nu.is_integer is False:
|
348 |
+
return csc(pi*nu)*(cos(pi*nu)*besselj(nu, z) - besselj(-nu, z))
|
349 |
+
|
350 |
+
def _eval_rewrite_as_besseli(self, nu, z, **kwargs):
|
351 |
+
aj = self._eval_rewrite_as_besselj(*self.args)
|
352 |
+
if aj:
|
353 |
+
return aj.rewrite(besseli)
|
354 |
+
|
355 |
+
def _eval_rewrite_as_yn(self, nu, z, **kwargs):
|
356 |
+
return sqrt(2*z/pi) * yn(nu - S.Half, self.argument)
|
357 |
+
|
358 |
+
def _eval_as_leading_term(self, x, logx=None, cdir=0):
|
359 |
+
nu, z = self.args
|
360 |
+
try:
|
361 |
+
arg = z.as_leading_term(x)
|
362 |
+
except NotImplementedError:
|
363 |
+
return self
|
364 |
+
c, e = arg.as_coeff_exponent(x)
|
365 |
+
|
366 |
+
if e.is_positive:
|
367 |
+
term_one = ((2/pi)*log(z/2)*besselj(nu, z))
|
368 |
+
term_two = -(z/2)**(-nu)*factorial(nu - 1)/pi if (nu).is_positive else S.Zero
|
369 |
+
term_three = -(z/2)**nu/(pi*factorial(nu))*(digamma(nu + 1) - S.EulerGamma)
|
370 |
+
arg = Add(*[term_one, term_two, term_three]).as_leading_term(x, logx=logx)
|
371 |
+
return arg
|
372 |
+
elif e.is_negative:
|
373 |
+
cdir = 1 if cdir == 0 else cdir
|
374 |
+
sign = c*cdir**e
|
375 |
+
if not sign.is_negative:
|
376 |
+
# Refer Abramowitz and Stegun 1965, p. 364 for more information on
|
377 |
+
# asymptotic approximation of bessely function.
|
378 |
+
return sqrt(2)*(-sin(pi*nu/2 - z + pi/4) + 3*cos(pi*nu/2 - z + pi/4)/(8*z))*sqrt(1/z)/sqrt(pi)
|
379 |
+
return self
|
380 |
+
|
381 |
+
return super(bessely, self)._eval_as_leading_term(x, logx, cdir)
|
382 |
+
|
383 |
+
def _eval_is_extended_real(self):
|
384 |
+
nu, z = self.args
|
385 |
+
if nu.is_integer and z.is_positive:
|
386 |
+
return True
|
387 |
+
|
388 |
+
def _eval_nseries(self, x, n, logx, cdir=0):
|
389 |
+
# Refer https://functions.wolfram.com/Bessel-TypeFunctions/BesselY/06/01/04/01/02/0008/
|
390 |
+
# for more information on nseries expansion of bessely function.
|
391 |
+
from sympy.series.order import Order
|
392 |
+
nu, z = self.args
|
393 |
+
|
394 |
+
# In case of powers less than 1, number of terms need to be computed
|
395 |
+
# separately to avoid repeated callings of _eval_nseries with wrong n
|
396 |
+
try:
|
397 |
+
_, exp = z.leadterm(x)
|
398 |
+
except (ValueError, NotImplementedError):
|
399 |
+
return self
|
400 |
+
|
401 |
+
if exp.is_positive and nu.is_integer:
|
402 |
+
newn = ceiling(n/exp)
|
403 |
+
bn = besselj(nu, z)
|
404 |
+
a = ((2/pi)*log(z/2)*bn)._eval_nseries(x, n, logx, cdir)
|
405 |
+
|
406 |
+
b, c = [], []
|
407 |
+
o = Order(x**n, x)
|
408 |
+
r = (z/2)._eval_nseries(x, n, logx, cdir).removeO()
|
409 |
+
if r is S.Zero:
|
410 |
+
return o
|
411 |
+
t = (_mexpand(r**2) + o).removeO()
|
412 |
+
|
413 |
+
if nu > S.Zero:
|
414 |
+
term = r**(-nu)*factorial(nu - 1)/pi
|
415 |
+
b.append(term)
|
416 |
+
for k in range(1, nu):
|
417 |
+
denom = (nu - k)*k
|
418 |
+
if denom == S.Zero:
|
419 |
+
term *= t/k
|
420 |
+
else:
|
421 |
+
term *= t/denom
|
422 |
+
term = (_mexpand(term) + o).removeO()
|
423 |
+
b.append(term)
|
424 |
+
|
425 |
+
p = r**nu/(pi*factorial(nu))
|
426 |
+
term = p*(digamma(nu + 1) - S.EulerGamma)
|
427 |
+
c.append(term)
|
428 |
+
for k in range(1, (newn + 1)//2):
|
429 |
+
p *= -t/(k*(k + nu))
|
430 |
+
p = (_mexpand(p) + o).removeO()
|
431 |
+
term = p*(digamma(k + nu + 1) + digamma(k + 1))
|
432 |
+
c.append(term)
|
433 |
+
return a - Add(*b) - Add(*c) # Order term comes from a
|
434 |
+
|
435 |
+
return super(bessely, self)._eval_nseries(x, n, logx, cdir)
|
436 |
+
|
437 |
+
|
438 |
+
class besseli(BesselBase):
|
439 |
+
r"""
|
440 |
+
Modified Bessel function of the first kind.
|
441 |
+
|
442 |
+
Explanation
|
443 |
+
===========
|
444 |
+
|
445 |
+
The Bessel $I$ function is a solution to the modified Bessel equation
|
446 |
+
|
447 |
+
.. math ::
|
448 |
+
z^2 \frac{\mathrm{d}^2 w}{\mathrm{d}z^2}
|
449 |
+
+ z \frac{\mathrm{d}w}{\mathrm{d}z} + (z^2 + \nu^2)^2 w = 0.
|
450 |
+
|
451 |
+
It can be defined as
|
452 |
+
|
453 |
+
.. math ::
|
454 |
+
I_\nu(z) = i^{-\nu} J_\nu(iz),
|
455 |
+
|
456 |
+
where $J_\nu(z)$ is the Bessel function of the first kind.
|
457 |
+
|
458 |
+
Examples
|
459 |
+
========
|
460 |
+
|
461 |
+
>>> from sympy import besseli
|
462 |
+
>>> from sympy.abc import z, n
|
463 |
+
>>> besseli(n, z).diff(z)
|
464 |
+
besseli(n - 1, z)/2 + besseli(n + 1, z)/2
|
465 |
+
|
466 |
+
See Also
|
467 |
+
========
|
468 |
+
|
469 |
+
besselj, bessely, besselk
|
470 |
+
|
471 |
+
References
|
472 |
+
==========
|
473 |
+
|
474 |
+
.. [1] https://functions.wolfram.com/Bessel-TypeFunctions/BesselI/
|
475 |
+
|
476 |
+
"""
|
477 |
+
|
478 |
+
_a = -S.One
|
479 |
+
_b = S.One
|
480 |
+
|
481 |
+
@classmethod
|
482 |
+
def eval(cls, nu, z):
|
483 |
+
if z.is_zero:
|
484 |
+
if nu.is_zero:
|
485 |
+
return S.One
|
486 |
+
elif (nu.is_integer and nu.is_zero is False) or re(nu).is_positive:
|
487 |
+
return S.Zero
|
488 |
+
elif re(nu).is_negative and not (nu.is_integer is True):
|
489 |
+
return S.ComplexInfinity
|
490 |
+
elif nu.is_imaginary:
|
491 |
+
return S.NaN
|
492 |
+
if im(z) in (S.Infinity, S.NegativeInfinity):
|
493 |
+
return S.Zero
|
494 |
+
if z is S.Infinity:
|
495 |
+
return S.Infinity
|
496 |
+
if z is S.NegativeInfinity:
|
497 |
+
return (-1)**nu*S.Infinity
|
498 |
+
|
499 |
+
if z.could_extract_minus_sign():
|
500 |
+
return (z)**nu*(-z)**(-nu)*besseli(nu, -z)
|
501 |
+
if nu.is_integer:
|
502 |
+
if nu.could_extract_minus_sign():
|
503 |
+
return besseli(-nu, z)
|
504 |
+
newz = z.extract_multiplicatively(I)
|
505 |
+
if newz: # NOTE we don't want to change the function if z==0
|
506 |
+
return I**(-nu)*besselj(nu, -newz)
|
507 |
+
|
508 |
+
# branch handling:
|
509 |
+
if nu.is_integer:
|
510 |
+
newz = unpolarify(z)
|
511 |
+
if newz != z:
|
512 |
+
return besseli(nu, newz)
|
513 |
+
else:
|
514 |
+
newz, n = z.extract_branch_factor()
|
515 |
+
if n != 0:
|
516 |
+
return exp(2*n*pi*nu*I)*besseli(nu, newz)
|
517 |
+
nnu = unpolarify(nu)
|
518 |
+
if nu != nnu:
|
519 |
+
return besseli(nnu, z)
|
520 |
+
|
521 |
+
def _eval_rewrite_as_besselj(self, nu, z, **kwargs):
|
522 |
+
return exp(-I*pi*nu/2)*besselj(nu, polar_lift(I)*z)
|
523 |
+
|
524 |
+
def _eval_rewrite_as_bessely(self, nu, z, **kwargs):
|
525 |
+
aj = self._eval_rewrite_as_besselj(*self.args)
|
526 |
+
if aj:
|
527 |
+
return aj.rewrite(bessely)
|
528 |
+
|
529 |
+
def _eval_rewrite_as_jn(self, nu, z, **kwargs):
|
530 |
+
return self._eval_rewrite_as_besselj(*self.args).rewrite(jn)
|
531 |
+
|
532 |
+
def _eval_is_extended_real(self):
|
533 |
+
nu, z = self.args
|
534 |
+
if nu.is_integer and z.is_extended_real:
|
535 |
+
return True
|
536 |
+
|
537 |
+
def _eval_as_leading_term(self, x, logx=None, cdir=0):
|
538 |
+
nu, z = self.args
|
539 |
+
try:
|
540 |
+
arg = z.as_leading_term(x)
|
541 |
+
except NotImplementedError:
|
542 |
+
return self
|
543 |
+
c, e = arg.as_coeff_exponent(x)
|
544 |
+
|
545 |
+
if e.is_positive:
|
546 |
+
return arg**nu/(2**nu*gamma(nu + 1))
|
547 |
+
elif e.is_negative:
|
548 |
+
cdir = 1 if cdir == 0 else cdir
|
549 |
+
sign = c*cdir**e
|
550 |
+
if not sign.is_negative:
|
551 |
+
# Refer Abramowitz and Stegun 1965, p. 377 for more information on
|
552 |
+
# asymptotic approximation of besseli function.
|
553 |
+
return exp(z)/sqrt(2*pi*z)
|
554 |
+
return self
|
555 |
+
|
556 |
+
return super(besseli, self)._eval_as_leading_term(x, logx, cdir)
|
557 |
+
|
558 |
+
def _eval_nseries(self, x, n, logx, cdir=0):
|
559 |
+
# Refer https://functions.wolfram.com/Bessel-TypeFunctions/BesselI/06/01/04/01/01/0003/
|
560 |
+
# for more information on nseries expansion of besseli function.
|
561 |
+
from sympy.series.order import Order
|
562 |
+
nu, z = self.args
|
563 |
+
|
564 |
+
# In case of powers less than 1, number of terms need to be computed
|
565 |
+
# separately to avoid repeated callings of _eval_nseries with wrong n
|
566 |
+
try:
|
567 |
+
_, exp = z.leadterm(x)
|
568 |
+
except (ValueError, NotImplementedError):
|
569 |
+
return self
|
570 |
+
|
571 |
+
if exp.is_positive:
|
572 |
+
newn = ceiling(n/exp)
|
573 |
+
o = Order(x**n, x)
|
574 |
+
r = (z/2)._eval_nseries(x, n, logx, cdir).removeO()
|
575 |
+
if r is S.Zero:
|
576 |
+
return o
|
577 |
+
t = (_mexpand(r**2) + o).removeO()
|
578 |
+
|
579 |
+
term = r**nu/gamma(nu + 1)
|
580 |
+
s = [term]
|
581 |
+
for k in range(1, (newn + 1)//2):
|
582 |
+
term *= t/(k*(nu + k))
|
583 |
+
term = (_mexpand(term) + o).removeO()
|
584 |
+
s.append(term)
|
585 |
+
return Add(*s) + o
|
586 |
+
|
587 |
+
return super(besseli, self)._eval_nseries(x, n, logx, cdir)
|
588 |
+
|
589 |
+
|
590 |
+
class besselk(BesselBase):
|
591 |
+
r"""
|
592 |
+
Modified Bessel function of the second kind.
|
593 |
+
|
594 |
+
Explanation
|
595 |
+
===========
|
596 |
+
|
597 |
+
The Bessel $K$ function of order $\nu$ is defined as
|
598 |
+
|
599 |
+
.. math ::
|
600 |
+
K_\nu(z) = \lim_{\mu \to \nu} \frac{\pi}{2}
|
601 |
+
\frac{I_{-\mu}(z) -I_\mu(z)}{\sin(\pi \mu)},
|
602 |
+
|
603 |
+
where $I_\mu(z)$ is the modified Bessel function of the first kind.
|
604 |
+
|
605 |
+
It is a solution of the modified Bessel equation, and linearly independent
|
606 |
+
from $Y_\nu$.
|
607 |
+
|
608 |
+
Examples
|
609 |
+
========
|
610 |
+
|
611 |
+
>>> from sympy import besselk
|
612 |
+
>>> from sympy.abc import z, n
|
613 |
+
>>> besselk(n, z).diff(z)
|
614 |
+
-besselk(n - 1, z)/2 - besselk(n + 1, z)/2
|
615 |
+
|
616 |
+
See Also
|
617 |
+
========
|
618 |
+
|
619 |
+
besselj, besseli, bessely
|
620 |
+
|
621 |
+
References
|
622 |
+
==========
|
623 |
+
|
624 |
+
.. [1] https://functions.wolfram.com/Bessel-TypeFunctions/BesselK/
|
625 |
+
|
626 |
+
"""
|
627 |
+
|
628 |
+
_a = S.One
|
629 |
+
_b = -S.One
|
630 |
+
|
631 |
+
@classmethod
|
632 |
+
def eval(cls, nu, z):
|
633 |
+
if z.is_zero:
|
634 |
+
if nu.is_zero:
|
635 |
+
return S.Infinity
|
636 |
+
elif re(nu).is_zero is False:
|
637 |
+
return S.ComplexInfinity
|
638 |
+
elif re(nu).is_zero:
|
639 |
+
return S.NaN
|
640 |
+
if z in (S.Infinity, I*S.Infinity, I*S.NegativeInfinity):
|
641 |
+
return S.Zero
|
642 |
+
|
643 |
+
if nu.is_integer:
|
644 |
+
if nu.could_extract_minus_sign():
|
645 |
+
return besselk(-nu, z)
|
646 |
+
|
647 |
+
def _eval_rewrite_as_besseli(self, nu, z, **kwargs):
|
648 |
+
if nu.is_integer is False:
|
649 |
+
return pi*csc(pi*nu)*(besseli(-nu, z) - besseli(nu, z))/2
|
650 |
+
|
651 |
+
def _eval_rewrite_as_besselj(self, nu, z, **kwargs):
|
652 |
+
ai = self._eval_rewrite_as_besseli(*self.args)
|
653 |
+
if ai:
|
654 |
+
return ai.rewrite(besselj)
|
655 |
+
|
656 |
+
def _eval_rewrite_as_bessely(self, nu, z, **kwargs):
|
657 |
+
aj = self._eval_rewrite_as_besselj(*self.args)
|
658 |
+
if aj:
|
659 |
+
return aj.rewrite(bessely)
|
660 |
+
|
661 |
+
def _eval_rewrite_as_yn(self, nu, z, **kwargs):
|
662 |
+
ay = self._eval_rewrite_as_bessely(*self.args)
|
663 |
+
if ay:
|
664 |
+
return ay.rewrite(yn)
|
665 |
+
|
666 |
+
def _eval_is_extended_real(self):
|
667 |
+
nu, z = self.args
|
668 |
+
if nu.is_integer and z.is_positive:
|
669 |
+
return True
|
670 |
+
|
671 |
+
def _eval_as_leading_term(self, x, logx=None, cdir=0):
|
672 |
+
nu, z = self.args
|
673 |
+
try:
|
674 |
+
arg = z.as_leading_term(x)
|
675 |
+
except NotImplementedError:
|
676 |
+
return self
|
677 |
+
_, e = arg.as_coeff_exponent(x)
|
678 |
+
|
679 |
+
if e.is_positive:
|
680 |
+
term_one = ((-1)**(nu -1)*log(z/2)*besseli(nu, z))
|
681 |
+
term_two = (z/2)**(-nu)*factorial(nu - 1)/2 if (nu).is_positive else S.Zero
|
682 |
+
term_three = (-1)**nu*(z/2)**nu/(2*factorial(nu))*(digamma(nu + 1) - S.EulerGamma)
|
683 |
+
arg = Add(*[term_one, term_two, term_three]).as_leading_term(x, logx=logx)
|
684 |
+
return arg
|
685 |
+
elif e.is_negative:
|
686 |
+
# Refer Abramowitz and Stegun 1965, p. 378 for more information on
|
687 |
+
# asymptotic approximation of besselk function.
|
688 |
+
return sqrt(pi)*exp(-z)/sqrt(2*z)
|
689 |
+
|
690 |
+
return super(besselk, self)._eval_as_leading_term(x, logx, cdir)
|
691 |
+
|
692 |
+
def _eval_nseries(self, x, n, logx, cdir=0):
|
693 |
+
# Refer https://functions.wolfram.com/Bessel-TypeFunctions/BesselK/06/01/04/01/02/0008/
|
694 |
+
# for more information on nseries expansion of besselk function.
|
695 |
+
from sympy.series.order import Order
|
696 |
+
nu, z = self.args
|
697 |
+
|
698 |
+
# In case of powers less than 1, number of terms need to be computed
|
699 |
+
# separately to avoid repeated callings of _eval_nseries with wrong n
|
700 |
+
try:
|
701 |
+
_, exp = z.leadterm(x)
|
702 |
+
except (ValueError, NotImplementedError):
|
703 |
+
return self
|
704 |
+
|
705 |
+
if exp.is_positive and nu.is_integer:
|
706 |
+
newn = ceiling(n/exp)
|
707 |
+
bn = besseli(nu, z)
|
708 |
+
a = ((-1)**(nu - 1)*log(z/2)*bn)._eval_nseries(x, n, logx, cdir)
|
709 |
+
|
710 |
+
b, c = [], []
|
711 |
+
o = Order(x**n, x)
|
712 |
+
r = (z/2)._eval_nseries(x, n, logx, cdir).removeO()
|
713 |
+
if r is S.Zero:
|
714 |
+
return o
|
715 |
+
t = (_mexpand(r**2) + o).removeO()
|
716 |
+
|
717 |
+
if nu > S.Zero:
|
718 |
+
term = r**(-nu)*factorial(nu - 1)/2
|
719 |
+
b.append(term)
|
720 |
+
for k in range(1, nu):
|
721 |
+
denom = (k - nu)*k
|
722 |
+
if denom == S.Zero:
|
723 |
+
term *= t/k
|
724 |
+
else:
|
725 |
+
term *= t/denom
|
726 |
+
term = (_mexpand(term) + o).removeO()
|
727 |
+
b.append(term)
|
728 |
+
|
729 |
+
p = r**nu*(-1)**nu/(2*factorial(nu))
|
730 |
+
term = p*(digamma(nu + 1) - S.EulerGamma)
|
731 |
+
c.append(term)
|
732 |
+
for k in range(1, (newn + 1)//2):
|
733 |
+
p *= t/(k*(k + nu))
|
734 |
+
p = (_mexpand(p) + o).removeO()
|
735 |
+
term = p*(digamma(k + nu + 1) + digamma(k + 1))
|
736 |
+
c.append(term)
|
737 |
+
return a + Add(*b) + Add(*c) # Order term comes from a
|
738 |
+
|
739 |
+
return super(besselk, self)._eval_nseries(x, n, logx, cdir)
|
740 |
+
|
741 |
+
|
742 |
+
class hankel1(BesselBase):
|
743 |
+
r"""
|
744 |
+
Hankel function of the first kind.
|
745 |
+
|
746 |
+
Explanation
|
747 |
+
===========
|
748 |
+
|
749 |
+
This function is defined as
|
750 |
+
|
751 |
+
.. math ::
|
752 |
+
H_\nu^{(1)} = J_\nu(z) + iY_\nu(z),
|
753 |
+
|
754 |
+
where $J_\nu(z)$ is the Bessel function of the first kind, and
|
755 |
+
$Y_\nu(z)$ is the Bessel function of the second kind.
|
756 |
+
|
757 |
+
It is a solution to Bessel's equation.
|
758 |
+
|
759 |
+
Examples
|
760 |
+
========
|
761 |
+
|
762 |
+
>>> from sympy import hankel1
|
763 |
+
>>> from sympy.abc import z, n
|
764 |
+
>>> hankel1(n, z).diff(z)
|
765 |
+
hankel1(n - 1, z)/2 - hankel1(n + 1, z)/2
|
766 |
+
|
767 |
+
See Also
|
768 |
+
========
|
769 |
+
|
770 |
+
hankel2, besselj, bessely
|
771 |
+
|
772 |
+
References
|
773 |
+
==========
|
774 |
+
|
775 |
+
.. [1] https://functions.wolfram.com/Bessel-TypeFunctions/HankelH1/
|
776 |
+
|
777 |
+
"""
|
778 |
+
|
779 |
+
_a = S.One
|
780 |
+
_b = S.One
|
781 |
+
|
782 |
+
def _eval_conjugate(self):
|
783 |
+
z = self.argument
|
784 |
+
if z.is_extended_negative is False:
|
785 |
+
return hankel2(self.order.conjugate(), z.conjugate())
|
786 |
+
|
787 |
+
|
788 |
+
class hankel2(BesselBase):
|
789 |
+
r"""
|
790 |
+
Hankel function of the second kind.
|
791 |
+
|
792 |
+
Explanation
|
793 |
+
===========
|
794 |
+
|
795 |
+
This function is defined as
|
796 |
+
|
797 |
+
.. math ::
|
798 |
+
H_\nu^{(2)} = J_\nu(z) - iY_\nu(z),
|
799 |
+
|
800 |
+
where $J_\nu(z)$ is the Bessel function of the first kind, and
|
801 |
+
$Y_\nu(z)$ is the Bessel function of the second kind.
|
802 |
+
|
803 |
+
It is a solution to Bessel's equation, and linearly independent from
|
804 |
+
$H_\nu^{(1)}$.
|
805 |
+
|
806 |
+
Examples
|
807 |
+
========
|
808 |
+
|
809 |
+
>>> from sympy import hankel2
|
810 |
+
>>> from sympy.abc import z, n
|
811 |
+
>>> hankel2(n, z).diff(z)
|
812 |
+
hankel2(n - 1, z)/2 - hankel2(n + 1, z)/2
|
813 |
+
|
814 |
+
See Also
|
815 |
+
========
|
816 |
+
|
817 |
+
hankel1, besselj, bessely
|
818 |
+
|
819 |
+
References
|
820 |
+
==========
|
821 |
+
|
822 |
+
.. [1] https://functions.wolfram.com/Bessel-TypeFunctions/HankelH2/
|
823 |
+
|
824 |
+
"""
|
825 |
+
|
826 |
+
_a = S.One
|
827 |
+
_b = S.One
|
828 |
+
|
829 |
+
def _eval_conjugate(self):
|
830 |
+
z = self.argument
|
831 |
+
if z.is_extended_negative is False:
|
832 |
+
return hankel1(self.order.conjugate(), z.conjugate())
|
833 |
+
|
834 |
+
|
835 |
+
def assume_integer_order(fn):
|
836 |
+
@wraps(fn)
|
837 |
+
def g(self, nu, z):
|
838 |
+
if nu.is_integer:
|
839 |
+
return fn(self, nu, z)
|
840 |
+
return g
|
841 |
+
|
842 |
+
|
843 |
+
class SphericalBesselBase(BesselBase):
|
844 |
+
"""
|
845 |
+
Base class for spherical Bessel functions.
|
846 |
+
|
847 |
+
These are thin wrappers around ordinary Bessel functions,
|
848 |
+
since spherical Bessel functions differ from the ordinary
|
849 |
+
ones just by a slight change in order.
|
850 |
+
|
851 |
+
To use this class, define the ``_eval_evalf()`` and ``_expand()`` methods.
|
852 |
+
|
853 |
+
"""
|
854 |
+
|
855 |
+
def _expand(self, **hints):
|
856 |
+
""" Expand self into a polynomial. Nu is guaranteed to be Integer. """
|
857 |
+
raise NotImplementedError('expansion')
|
858 |
+
|
859 |
+
def _eval_expand_func(self, **hints):
|
860 |
+
if self.order.is_Integer:
|
861 |
+
return self._expand(**hints)
|
862 |
+
return self
|
863 |
+
|
864 |
+
def fdiff(self, argindex=2):
|
865 |
+
if argindex != 2:
|
866 |
+
raise ArgumentIndexError(self, argindex)
|
867 |
+
return self.__class__(self.order - 1, self.argument) - \
|
868 |
+
self * (self.order + 1)/self.argument
|
869 |
+
|
870 |
+
|
871 |
+
def _jn(n, z):
|
872 |
+
return (spherical_bessel_fn(n, z)*sin(z) +
|
873 |
+
S.NegativeOne**(n + 1)*spherical_bessel_fn(-n - 1, z)*cos(z))
|
874 |
+
|
875 |
+
|
876 |
+
def _yn(n, z):
|
877 |
+
# (-1)**(n + 1) * _jn(-n - 1, z)
|
878 |
+
return (S.NegativeOne**(n + 1) * spherical_bessel_fn(-n - 1, z)*sin(z) -
|
879 |
+
spherical_bessel_fn(n, z)*cos(z))
|
880 |
+
|
881 |
+
|
882 |
+
class jn(SphericalBesselBase):
|
883 |
+
r"""
|
884 |
+
Spherical Bessel function of the first kind.
|
885 |
+
|
886 |
+
Explanation
|
887 |
+
===========
|
888 |
+
|
889 |
+
This function is a solution to the spherical Bessel equation
|
890 |
+
|
891 |
+
.. math ::
|
892 |
+
z^2 \frac{\mathrm{d}^2 w}{\mathrm{d}z^2}
|
893 |
+
+ 2z \frac{\mathrm{d}w}{\mathrm{d}z} + (z^2 - \nu(\nu + 1)) w = 0.
|
894 |
+
|
895 |
+
It can be defined as
|
896 |
+
|
897 |
+
.. math ::
|
898 |
+
j_\nu(z) = \sqrt{\frac{\pi}{2z}} J_{\nu + \frac{1}{2}}(z),
|
899 |
+
|
900 |
+
where $J_\nu(z)$ is the Bessel function of the first kind.
|
901 |
+
|
902 |
+
The spherical Bessel functions of integral order are
|
903 |
+
calculated using the formula:
|
904 |
+
|
905 |
+
.. math:: j_n(z) = f_n(z) \sin{z} + (-1)^{n+1} f_{-n-1}(z) \cos{z},
|
906 |
+
|
907 |
+
where the coefficients $f_n(z)$ are available as
|
908 |
+
:func:`sympy.polys.orthopolys.spherical_bessel_fn`.
|
909 |
+
|
910 |
+
Examples
|
911 |
+
========
|
912 |
+
|
913 |
+
>>> from sympy import Symbol, jn, sin, cos, expand_func, besselj, bessely
|
914 |
+
>>> z = Symbol("z")
|
915 |
+
>>> nu = Symbol("nu", integer=True)
|
916 |
+
>>> print(expand_func(jn(0, z)))
|
917 |
+
sin(z)/z
|
918 |
+
>>> expand_func(jn(1, z)) == sin(z)/z**2 - cos(z)/z
|
919 |
+
True
|
920 |
+
>>> expand_func(jn(3, z))
|
921 |
+
(-6/z**2 + 15/z**4)*sin(z) + (1/z - 15/z**3)*cos(z)
|
922 |
+
>>> jn(nu, z).rewrite(besselj)
|
923 |
+
sqrt(2)*sqrt(pi)*sqrt(1/z)*besselj(nu + 1/2, z)/2
|
924 |
+
>>> jn(nu, z).rewrite(bessely)
|
925 |
+
(-1)**nu*sqrt(2)*sqrt(pi)*sqrt(1/z)*bessely(-nu - 1/2, z)/2
|
926 |
+
>>> jn(2, 5.2+0.3j).evalf(20)
|
927 |
+
0.099419756723640344491 - 0.054525080242173562897*I
|
928 |
+
|
929 |
+
See Also
|
930 |
+
========
|
931 |
+
|
932 |
+
besselj, bessely, besselk, yn
|
933 |
+
|
934 |
+
References
|
935 |
+
==========
|
936 |
+
|
937 |
+
.. [1] https://dlmf.nist.gov/10.47
|
938 |
+
|
939 |
+
"""
|
940 |
+
@classmethod
|
941 |
+
def eval(cls, nu, z):
|
942 |
+
if z.is_zero:
|
943 |
+
if nu.is_zero:
|
944 |
+
return S.One
|
945 |
+
elif nu.is_integer:
|
946 |
+
if nu.is_positive:
|
947 |
+
return S.Zero
|
948 |
+
else:
|
949 |
+
return S.ComplexInfinity
|
950 |
+
if z in (S.NegativeInfinity, S.Infinity):
|
951 |
+
return S.Zero
|
952 |
+
|
953 |
+
def _eval_rewrite_as_besselj(self, nu, z, **kwargs):
|
954 |
+
return sqrt(pi/(2*z)) * besselj(nu + S.Half, z)
|
955 |
+
|
956 |
+
def _eval_rewrite_as_bessely(self, nu, z, **kwargs):
|
957 |
+
return S.NegativeOne**nu * sqrt(pi/(2*z)) * bessely(-nu - S.Half, z)
|
958 |
+
|
959 |
+
def _eval_rewrite_as_yn(self, nu, z, **kwargs):
|
960 |
+
return S.NegativeOne**(nu) * yn(-nu - 1, z)
|
961 |
+
|
962 |
+
def _expand(self, **hints):
|
963 |
+
return _jn(self.order, self.argument)
|
964 |
+
|
965 |
+
def _eval_evalf(self, prec):
|
966 |
+
if self.order.is_Integer:
|
967 |
+
return self.rewrite(besselj)._eval_evalf(prec)
|
968 |
+
|
969 |
+
|
970 |
+
class yn(SphericalBesselBase):
|
971 |
+
r"""
|
972 |
+
Spherical Bessel function of the second kind.
|
973 |
+
|
974 |
+
Explanation
|
975 |
+
===========
|
976 |
+
|
977 |
+
This function is another solution to the spherical Bessel equation, and
|
978 |
+
linearly independent from $j_n$. It can be defined as
|
979 |
+
|
980 |
+
.. math ::
|
981 |
+
y_\nu(z) = \sqrt{\frac{\pi}{2z}} Y_{\nu + \frac{1}{2}}(z),
|
982 |
+
|
983 |
+
where $Y_\nu(z)$ is the Bessel function of the second kind.
|
984 |
+
|
985 |
+
For integral orders $n$, $y_n$ is calculated using the formula:
|
986 |
+
|
987 |
+
.. math:: y_n(z) = (-1)^{n+1} j_{-n-1}(z)
|
988 |
+
|
989 |
+
Examples
|
990 |
+
========
|
991 |
+
|
992 |
+
>>> from sympy import Symbol, yn, sin, cos, expand_func, besselj, bessely
|
993 |
+
>>> z = Symbol("z")
|
994 |
+
>>> nu = Symbol("nu", integer=True)
|
995 |
+
>>> print(expand_func(yn(0, z)))
|
996 |
+
-cos(z)/z
|
997 |
+
>>> expand_func(yn(1, z)) == -cos(z)/z**2-sin(z)/z
|
998 |
+
True
|
999 |
+
>>> yn(nu, z).rewrite(besselj)
|
1000 |
+
(-1)**(nu + 1)*sqrt(2)*sqrt(pi)*sqrt(1/z)*besselj(-nu - 1/2, z)/2
|
1001 |
+
>>> yn(nu, z).rewrite(bessely)
|
1002 |
+
sqrt(2)*sqrt(pi)*sqrt(1/z)*bessely(nu + 1/2, z)/2
|
1003 |
+
>>> yn(2, 5.2+0.3j).evalf(20)
|
1004 |
+
0.18525034196069722536 + 0.014895573969924817587*I
|
1005 |
+
|
1006 |
+
See Also
|
1007 |
+
========
|
1008 |
+
|
1009 |
+
besselj, bessely, besselk, jn
|
1010 |
+
|
1011 |
+
References
|
1012 |
+
==========
|
1013 |
+
|
1014 |
+
.. [1] https://dlmf.nist.gov/10.47
|
1015 |
+
|
1016 |
+
"""
|
1017 |
+
@assume_integer_order
|
1018 |
+
def _eval_rewrite_as_besselj(self, nu, z, **kwargs):
|
1019 |
+
return S.NegativeOne**(nu+1) * sqrt(pi/(2*z)) * besselj(-nu - S.Half, z)
|
1020 |
+
|
1021 |
+
@assume_integer_order
|
1022 |
+
def _eval_rewrite_as_bessely(self, nu, z, **kwargs):
|
1023 |
+
return sqrt(pi/(2*z)) * bessely(nu + S.Half, z)
|
1024 |
+
|
1025 |
+
def _eval_rewrite_as_jn(self, nu, z, **kwargs):
|
1026 |
+
return S.NegativeOne**(nu + 1) * jn(-nu - 1, z)
|
1027 |
+
|
1028 |
+
def _expand(self, **hints):
|
1029 |
+
return _yn(self.order, self.argument)
|
1030 |
+
|
1031 |
+
def _eval_evalf(self, prec):
|
1032 |
+
if self.order.is_Integer:
|
1033 |
+
return self.rewrite(bessely)._eval_evalf(prec)
|
1034 |
+
|
1035 |
+
|
1036 |
+
class SphericalHankelBase(SphericalBesselBase):
|
1037 |
+
|
1038 |
+
@assume_integer_order
|
1039 |
+
def _eval_rewrite_as_besselj(self, nu, z, **kwargs):
|
1040 |
+
# jn +- I*yn
|
1041 |
+
# jn as beeselj: sqrt(pi/(2*z)) * besselj(nu + S.Half, z)
|
1042 |
+
# yn as besselj: (-1)**(nu+1) * sqrt(pi/(2*z)) * besselj(-nu - S.Half, z)
|
1043 |
+
hks = self._hankel_kind_sign
|
1044 |
+
return sqrt(pi/(2*z))*(besselj(nu + S.Half, z) +
|
1045 |
+
hks*I*S.NegativeOne**(nu+1)*besselj(-nu - S.Half, z))
|
1046 |
+
|
1047 |
+
@assume_integer_order
|
1048 |
+
def _eval_rewrite_as_bessely(self, nu, z, **kwargs):
|
1049 |
+
# jn +- I*yn
|
1050 |
+
# jn as bessely: (-1)**nu * sqrt(pi/(2*z)) * bessely(-nu - S.Half, z)
|
1051 |
+
# yn as bessely: sqrt(pi/(2*z)) * bessely(nu + S.Half, z)
|
1052 |
+
hks = self._hankel_kind_sign
|
1053 |
+
return sqrt(pi/(2*z))*(S.NegativeOne**nu*bessely(-nu - S.Half, z) +
|
1054 |
+
hks*I*bessely(nu + S.Half, z))
|
1055 |
+
|
1056 |
+
def _eval_rewrite_as_yn(self, nu, z, **kwargs):
|
1057 |
+
hks = self._hankel_kind_sign
|
1058 |
+
return jn(nu, z).rewrite(yn) + hks*I*yn(nu, z)
|
1059 |
+
|
1060 |
+
def _eval_rewrite_as_jn(self, nu, z, **kwargs):
|
1061 |
+
hks = self._hankel_kind_sign
|
1062 |
+
return jn(nu, z) + hks*I*yn(nu, z).rewrite(jn)
|
1063 |
+
|
1064 |
+
def _eval_expand_func(self, **hints):
|
1065 |
+
if self.order.is_Integer:
|
1066 |
+
return self._expand(**hints)
|
1067 |
+
else:
|
1068 |
+
nu = self.order
|
1069 |
+
z = self.argument
|
1070 |
+
hks = self._hankel_kind_sign
|
1071 |
+
return jn(nu, z) + hks*I*yn(nu, z)
|
1072 |
+
|
1073 |
+
def _expand(self, **hints):
|
1074 |
+
n = self.order
|
1075 |
+
z = self.argument
|
1076 |
+
hks = self._hankel_kind_sign
|
1077 |
+
|
1078 |
+
# fully expanded version
|
1079 |
+
# return ((fn(n, z) * sin(z) +
|
1080 |
+
# (-1)**(n + 1) * fn(-n - 1, z) * cos(z)) + # jn
|
1081 |
+
# (hks * I * (-1)**(n + 1) *
|
1082 |
+
# (fn(-n - 1, z) * hk * I * sin(z) +
|
1083 |
+
# (-1)**(-n) * fn(n, z) * I * cos(z))) # +-I*yn
|
1084 |
+
# )
|
1085 |
+
|
1086 |
+
return (_jn(n, z) + hks*I*_yn(n, z)).expand()
|
1087 |
+
|
1088 |
+
def _eval_evalf(self, prec):
|
1089 |
+
if self.order.is_Integer:
|
1090 |
+
return self.rewrite(besselj)._eval_evalf(prec)
|
1091 |
+
|
1092 |
+
|
1093 |
+
class hn1(SphericalHankelBase):
|
1094 |
+
r"""
|
1095 |
+
Spherical Hankel function of the first kind.
|
1096 |
+
|
1097 |
+
Explanation
|
1098 |
+
===========
|
1099 |
+
|
1100 |
+
This function is defined as
|
1101 |
+
|
1102 |
+
.. math:: h_\nu^(1)(z) = j_\nu(z) + i y_\nu(z),
|
1103 |
+
|
1104 |
+
where $j_\nu(z)$ and $y_\nu(z)$ are the spherical
|
1105 |
+
Bessel function of the first and second kinds.
|
1106 |
+
|
1107 |
+
For integral orders $n$, $h_n^(1)$ is calculated using the formula:
|
1108 |
+
|
1109 |
+
.. math:: h_n^(1)(z) = j_{n}(z) + i (-1)^{n+1} j_{-n-1}(z)
|
1110 |
+
|
1111 |
+
Examples
|
1112 |
+
========
|
1113 |
+
|
1114 |
+
>>> from sympy import Symbol, hn1, hankel1, expand_func, yn, jn
|
1115 |
+
>>> z = Symbol("z")
|
1116 |
+
>>> nu = Symbol("nu", integer=True)
|
1117 |
+
>>> print(expand_func(hn1(nu, z)))
|
1118 |
+
jn(nu, z) + I*yn(nu, z)
|
1119 |
+
>>> print(expand_func(hn1(0, z)))
|
1120 |
+
sin(z)/z - I*cos(z)/z
|
1121 |
+
>>> print(expand_func(hn1(1, z)))
|
1122 |
+
-I*sin(z)/z - cos(z)/z + sin(z)/z**2 - I*cos(z)/z**2
|
1123 |
+
>>> hn1(nu, z).rewrite(jn)
|
1124 |
+
(-1)**(nu + 1)*I*jn(-nu - 1, z) + jn(nu, z)
|
1125 |
+
>>> hn1(nu, z).rewrite(yn)
|
1126 |
+
(-1)**nu*yn(-nu - 1, z) + I*yn(nu, z)
|
1127 |
+
>>> hn1(nu, z).rewrite(hankel1)
|
1128 |
+
sqrt(2)*sqrt(pi)*sqrt(1/z)*hankel1(nu, z)/2
|
1129 |
+
|
1130 |
+
See Also
|
1131 |
+
========
|
1132 |
+
|
1133 |
+
hn2, jn, yn, hankel1, hankel2
|
1134 |
+
|
1135 |
+
References
|
1136 |
+
==========
|
1137 |
+
|
1138 |
+
.. [1] https://dlmf.nist.gov/10.47
|
1139 |
+
|
1140 |
+
"""
|
1141 |
+
|
1142 |
+
_hankel_kind_sign = S.One
|
1143 |
+
|
1144 |
+
@assume_integer_order
|
1145 |
+
def _eval_rewrite_as_hankel1(self, nu, z, **kwargs):
|
1146 |
+
return sqrt(pi/(2*z))*hankel1(nu, z)
|
1147 |
+
|
1148 |
+
|
1149 |
+
class hn2(SphericalHankelBase):
|
1150 |
+
r"""
|
1151 |
+
Spherical Hankel function of the second kind.
|
1152 |
+
|
1153 |
+
Explanation
|
1154 |
+
===========
|
1155 |
+
|
1156 |
+
This function is defined as
|
1157 |
+
|
1158 |
+
.. math:: h_\nu^(2)(z) = j_\nu(z) - i y_\nu(z),
|
1159 |
+
|
1160 |
+
where $j_\nu(z)$ and $y_\nu(z)$ are the spherical
|
1161 |
+
Bessel function of the first and second kinds.
|
1162 |
+
|
1163 |
+
For integral orders $n$, $h_n^(2)$ is calculated using the formula:
|
1164 |
+
|
1165 |
+
.. math:: h_n^(2)(z) = j_{n} - i (-1)^{n+1} j_{-n-1}(z)
|
1166 |
+
|
1167 |
+
Examples
|
1168 |
+
========
|
1169 |
+
|
1170 |
+
>>> from sympy import Symbol, hn2, hankel2, expand_func, jn, yn
|
1171 |
+
>>> z = Symbol("z")
|
1172 |
+
>>> nu = Symbol("nu", integer=True)
|
1173 |
+
>>> print(expand_func(hn2(nu, z)))
|
1174 |
+
jn(nu, z) - I*yn(nu, z)
|
1175 |
+
>>> print(expand_func(hn2(0, z)))
|
1176 |
+
sin(z)/z + I*cos(z)/z
|
1177 |
+
>>> print(expand_func(hn2(1, z)))
|
1178 |
+
I*sin(z)/z - cos(z)/z + sin(z)/z**2 + I*cos(z)/z**2
|
1179 |
+
>>> hn2(nu, z).rewrite(hankel2)
|
1180 |
+
sqrt(2)*sqrt(pi)*sqrt(1/z)*hankel2(nu, z)/2
|
1181 |
+
>>> hn2(nu, z).rewrite(jn)
|
1182 |
+
-(-1)**(nu + 1)*I*jn(-nu - 1, z) + jn(nu, z)
|
1183 |
+
>>> hn2(nu, z).rewrite(yn)
|
1184 |
+
(-1)**nu*yn(-nu - 1, z) - I*yn(nu, z)
|
1185 |
+
|
1186 |
+
See Also
|
1187 |
+
========
|
1188 |
+
|
1189 |
+
hn1, jn, yn, hankel1, hankel2
|
1190 |
+
|
1191 |
+
References
|
1192 |
+
==========
|
1193 |
+
|
1194 |
+
.. [1] https://dlmf.nist.gov/10.47
|
1195 |
+
|
1196 |
+
"""
|
1197 |
+
|
1198 |
+
_hankel_kind_sign = -S.One
|
1199 |
+
|
1200 |
+
@assume_integer_order
|
1201 |
+
def _eval_rewrite_as_hankel2(self, nu, z, **kwargs):
|
1202 |
+
return sqrt(pi/(2*z))*hankel2(nu, z)
|
1203 |
+
|
1204 |
+
|
1205 |
+
def jn_zeros(n, k, method="sympy", dps=15):
|
1206 |
+
"""
|
1207 |
+
Zeros of the spherical Bessel function of the first kind.
|
1208 |
+
|
1209 |
+
Explanation
|
1210 |
+
===========
|
1211 |
+
|
1212 |
+
This returns an array of zeros of $jn$ up to the $k$-th zero.
|
1213 |
+
|
1214 |
+
* method = "sympy": uses `mpmath.besseljzero
|
1215 |
+
<https://mpmath.org/doc/current/functions/bessel.html#mpmath.besseljzero>`_
|
1216 |
+
* method = "scipy": uses the
|
1217 |
+
`SciPy's sph_jn <https://docs.scipy.org/doc/scipy/reference/generated/scipy.special.jn_zeros.html>`_
|
1218 |
+
and
|
1219 |
+
`newton <https://docs.scipy.org/doc/scipy/reference/generated/scipy.optimize.newton.html>`_
|
1220 |
+
to find all
|
1221 |
+
roots, which is faster than computing the zeros using a general
|
1222 |
+
numerical solver, but it requires SciPy and only works with low
|
1223 |
+
precision floating point numbers. (The function used with
|
1224 |
+
method="sympy" is a recent addition to mpmath; before that a general
|
1225 |
+
solver was used.)
|
1226 |
+
|
1227 |
+
Examples
|
1228 |
+
========
|
1229 |
+
|
1230 |
+
>>> from sympy import jn_zeros
|
1231 |
+
>>> jn_zeros(2, 4, dps=5)
|
1232 |
+
[5.7635, 9.095, 12.323, 15.515]
|
1233 |
+
|
1234 |
+
See Also
|
1235 |
+
========
|
1236 |
+
|
1237 |
+
jn, yn, besselj, besselk, bessely
|
1238 |
+
|
1239 |
+
Parameters
|
1240 |
+
==========
|
1241 |
+
|
1242 |
+
n : integer
|
1243 |
+
order of Bessel function
|
1244 |
+
|
1245 |
+
k : integer
|
1246 |
+
number of zeros to return
|
1247 |
+
|
1248 |
+
|
1249 |
+
"""
|
1250 |
+
from math import pi as math_pi
|
1251 |
+
|
1252 |
+
if method == "sympy":
|
1253 |
+
from mpmath import besseljzero
|
1254 |
+
from mpmath.libmp.libmpf import dps_to_prec
|
1255 |
+
prec = dps_to_prec(dps)
|
1256 |
+
return [Expr._from_mpmath(besseljzero(S(n + 0.5)._to_mpmath(prec),
|
1257 |
+
int(l)), prec)
|
1258 |
+
for l in range(1, k + 1)]
|
1259 |
+
elif method == "scipy":
|
1260 |
+
from scipy.optimize import newton
|
1261 |
+
try:
|
1262 |
+
from scipy.special import spherical_jn
|
1263 |
+
f = lambda x: spherical_jn(n, x)
|
1264 |
+
except ImportError:
|
1265 |
+
from scipy.special import sph_jn
|
1266 |
+
f = lambda x: sph_jn(n, x)[0][-1]
|
1267 |
+
else:
|
1268 |
+
raise NotImplementedError("Unknown method.")
|
1269 |
+
|
1270 |
+
def solver(f, x):
|
1271 |
+
if method == "scipy":
|
1272 |
+
root = newton(f, x)
|
1273 |
+
else:
|
1274 |
+
raise NotImplementedError("Unknown method.")
|
1275 |
+
return root
|
1276 |
+
|
1277 |
+
# we need to approximate the position of the first root:
|
1278 |
+
root = n + math_pi
|
1279 |
+
# determine the first root exactly:
|
1280 |
+
root = solver(f, root)
|
1281 |
+
roots = [root]
|
1282 |
+
for i in range(k - 1):
|
1283 |
+
# estimate the position of the next root using the last root + pi:
|
1284 |
+
root = solver(f, root + math_pi)
|
1285 |
+
roots.append(root)
|
1286 |
+
return roots
|
1287 |
+
|
1288 |
+
|
1289 |
+
class AiryBase(Function):
|
1290 |
+
"""
|
1291 |
+
Abstract base class for Airy functions.
|
1292 |
+
|
1293 |
+
This class is meant to reduce code duplication.
|
1294 |
+
|
1295 |
+
"""
|
1296 |
+
|
1297 |
+
def _eval_conjugate(self):
|
1298 |
+
return self.func(self.args[0].conjugate())
|
1299 |
+
|
1300 |
+
def _eval_is_extended_real(self):
|
1301 |
+
return self.args[0].is_extended_real
|
1302 |
+
|
1303 |
+
def as_real_imag(self, deep=True, **hints):
|
1304 |
+
z = self.args[0]
|
1305 |
+
zc = z.conjugate()
|
1306 |
+
f = self.func
|
1307 |
+
u = (f(z)+f(zc))/2
|
1308 |
+
v = I*(f(zc)-f(z))/2
|
1309 |
+
return u, v
|
1310 |
+
|
1311 |
+
def _eval_expand_complex(self, deep=True, **hints):
|
1312 |
+
re_part, im_part = self.as_real_imag(deep=deep, **hints)
|
1313 |
+
return re_part + im_part*I
|
1314 |
+
|
1315 |
+
|
1316 |
+
class airyai(AiryBase):
|
1317 |
+
r"""
|
1318 |
+
The Airy function $\operatorname{Ai}$ of the first kind.
|
1319 |
+
|
1320 |
+
Explanation
|
1321 |
+
===========
|
1322 |
+
|
1323 |
+
The Airy function $\operatorname{Ai}(z)$ is defined to be the function
|
1324 |
+
satisfying Airy's differential equation
|
1325 |
+
|
1326 |
+
.. math::
|
1327 |
+
\frac{\mathrm{d}^2 w(z)}{\mathrm{d}z^2} - z w(z) = 0.
|
1328 |
+
|
1329 |
+
Equivalently, for real $z$
|
1330 |
+
|
1331 |
+
.. math::
|
1332 |
+
\operatorname{Ai}(z) := \frac{1}{\pi}
|
1333 |
+
\int_0^\infty \cos\left(\frac{t^3}{3} + z t\right) \mathrm{d}t.
|
1334 |
+
|
1335 |
+
Examples
|
1336 |
+
========
|
1337 |
+
|
1338 |
+
Create an Airy function object:
|
1339 |
+
|
1340 |
+
>>> from sympy import airyai
|
1341 |
+
>>> from sympy.abc import z
|
1342 |
+
|
1343 |
+
>>> airyai(z)
|
1344 |
+
airyai(z)
|
1345 |
+
|
1346 |
+
Several special values are known:
|
1347 |
+
|
1348 |
+
>>> airyai(0)
|
1349 |
+
3**(1/3)/(3*gamma(2/3))
|
1350 |
+
>>> from sympy import oo
|
1351 |
+
>>> airyai(oo)
|
1352 |
+
0
|
1353 |
+
>>> airyai(-oo)
|
1354 |
+
0
|
1355 |
+
|
1356 |
+
The Airy function obeys the mirror symmetry:
|
1357 |
+
|
1358 |
+
>>> from sympy import conjugate
|
1359 |
+
>>> conjugate(airyai(z))
|
1360 |
+
airyai(conjugate(z))
|
1361 |
+
|
1362 |
+
Differentiation with respect to $z$ is supported:
|
1363 |
+
|
1364 |
+
>>> from sympy import diff
|
1365 |
+
>>> diff(airyai(z), z)
|
1366 |
+
airyaiprime(z)
|
1367 |
+
>>> diff(airyai(z), z, 2)
|
1368 |
+
z*airyai(z)
|
1369 |
+
|
1370 |
+
Series expansion is also supported:
|
1371 |
+
|
1372 |
+
>>> from sympy import series
|
1373 |
+
>>> series(airyai(z), z, 0, 3)
|
1374 |
+
3**(5/6)*gamma(1/3)/(6*pi) - 3**(1/6)*z*gamma(2/3)/(2*pi) + O(z**3)
|
1375 |
+
|
1376 |
+
We can numerically evaluate the Airy function to arbitrary precision
|
1377 |
+
on the whole complex plane:
|
1378 |
+
|
1379 |
+
>>> airyai(-2).evalf(50)
|
1380 |
+
0.22740742820168557599192443603787379946077222541710
|
1381 |
+
|
1382 |
+
Rewrite $\operatorname{Ai}(z)$ in terms of hypergeometric functions:
|
1383 |
+
|
1384 |
+
>>> from sympy import hyper
|
1385 |
+
>>> airyai(z).rewrite(hyper)
|
1386 |
+
-3**(2/3)*z*hyper((), (4/3,), z**3/9)/(3*gamma(1/3)) + 3**(1/3)*hyper((), (2/3,), z**3/9)/(3*gamma(2/3))
|
1387 |
+
|
1388 |
+
See Also
|
1389 |
+
========
|
1390 |
+
|
1391 |
+
airybi: Airy function of the second kind.
|
1392 |
+
airyaiprime: Derivative of the Airy function of the first kind.
|
1393 |
+
airybiprime: Derivative of the Airy function of the second kind.
|
1394 |
+
|
1395 |
+
References
|
1396 |
+
==========
|
1397 |
+
|
1398 |
+
.. [1] https://en.wikipedia.org/wiki/Airy_function
|
1399 |
+
.. [2] https://dlmf.nist.gov/9
|
1400 |
+
.. [3] https://encyclopediaofmath.org/wiki/Airy_functions
|
1401 |
+
.. [4] https://mathworld.wolfram.com/AiryFunctions.html
|
1402 |
+
|
1403 |
+
"""
|
1404 |
+
|
1405 |
+
nargs = 1
|
1406 |
+
unbranched = True
|
1407 |
+
|
1408 |
+
@classmethod
|
1409 |
+
def eval(cls, arg):
|
1410 |
+
if arg.is_Number:
|
1411 |
+
if arg is S.NaN:
|
1412 |
+
return S.NaN
|
1413 |
+
elif arg is S.Infinity:
|
1414 |
+
return S.Zero
|
1415 |
+
elif arg is S.NegativeInfinity:
|
1416 |
+
return S.Zero
|
1417 |
+
elif arg.is_zero:
|
1418 |
+
return S.One / (3**Rational(2, 3) * gamma(Rational(2, 3)))
|
1419 |
+
if arg.is_zero:
|
1420 |
+
return S.One / (3**Rational(2, 3) * gamma(Rational(2, 3)))
|
1421 |
+
|
1422 |
+
def fdiff(self, argindex=1):
|
1423 |
+
if argindex == 1:
|
1424 |
+
return airyaiprime(self.args[0])
|
1425 |
+
else:
|
1426 |
+
raise ArgumentIndexError(self, argindex)
|
1427 |
+
|
1428 |
+
@staticmethod
|
1429 |
+
@cacheit
|
1430 |
+
def taylor_term(n, x, *previous_terms):
|
1431 |
+
if n < 0:
|
1432 |
+
return S.Zero
|
1433 |
+
else:
|
1434 |
+
x = sympify(x)
|
1435 |
+
if len(previous_terms) > 1:
|
1436 |
+
p = previous_terms[-1]
|
1437 |
+
return ((cbrt(3)*x)**(-n)*(cbrt(3)*x)**(n + 1)*sin(pi*(n*Rational(2, 3) + Rational(4, 3)))*factorial(n) *
|
1438 |
+
gamma(n/3 + Rational(2, 3))/(sin(pi*(n*Rational(2, 3) + Rational(2, 3)))*factorial(n + 1)*gamma(n/3 + Rational(1, 3))) * p)
|
1439 |
+
else:
|
1440 |
+
return (S.One/(3**Rational(2, 3)*pi) * gamma((n+S.One)/S(3)) * sin(Rational(2, 3)*pi*(n+S.One)) /
|
1441 |
+
factorial(n) * (cbrt(3)*x)**n)
|
1442 |
+
|
1443 |
+
def _eval_rewrite_as_besselj(self, z, **kwargs):
|
1444 |
+
ot = Rational(1, 3)
|
1445 |
+
tt = Rational(2, 3)
|
1446 |
+
a = Pow(-z, Rational(3, 2))
|
1447 |
+
if re(z).is_negative:
|
1448 |
+
return ot*sqrt(-z) * (besselj(-ot, tt*a) + besselj(ot, tt*a))
|
1449 |
+
|
1450 |
+
def _eval_rewrite_as_besseli(self, z, **kwargs):
|
1451 |
+
ot = Rational(1, 3)
|
1452 |
+
tt = Rational(2, 3)
|
1453 |
+
a = Pow(z, Rational(3, 2))
|
1454 |
+
if re(z).is_positive:
|
1455 |
+
return ot*sqrt(z) * (besseli(-ot, tt*a) - besseli(ot, tt*a))
|
1456 |
+
else:
|
1457 |
+
return ot*(Pow(a, ot)*besseli(-ot, tt*a) - z*Pow(a, -ot)*besseli(ot, tt*a))
|
1458 |
+
|
1459 |
+
def _eval_rewrite_as_hyper(self, z, **kwargs):
|
1460 |
+
pf1 = S.One / (3**Rational(2, 3)*gamma(Rational(2, 3)))
|
1461 |
+
pf2 = z / (root(3, 3)*gamma(Rational(1, 3)))
|
1462 |
+
return pf1 * hyper([], [Rational(2, 3)], z**3/9) - pf2 * hyper([], [Rational(4, 3)], z**3/9)
|
1463 |
+
|
1464 |
+
def _eval_expand_func(self, **hints):
|
1465 |
+
arg = self.args[0]
|
1466 |
+
symbs = arg.free_symbols
|
1467 |
+
|
1468 |
+
if len(symbs) == 1:
|
1469 |
+
z = symbs.pop()
|
1470 |
+
c = Wild("c", exclude=[z])
|
1471 |
+
d = Wild("d", exclude=[z])
|
1472 |
+
m = Wild("m", exclude=[z])
|
1473 |
+
n = Wild("n", exclude=[z])
|
1474 |
+
M = arg.match(c*(d*z**n)**m)
|
1475 |
+
if M is not None:
|
1476 |
+
m = M[m]
|
1477 |
+
# The transformation is given by 03.05.16.0001.01
|
1478 |
+
# https://functions.wolfram.com/Bessel-TypeFunctions/AiryAi/16/01/01/0001/
|
1479 |
+
if (3*m).is_integer:
|
1480 |
+
c = M[c]
|
1481 |
+
d = M[d]
|
1482 |
+
n = M[n]
|
1483 |
+
pf = (d * z**n)**m / (d**m * z**(m*n))
|
1484 |
+
newarg = c * d**m * z**(m*n)
|
1485 |
+
return S.Half * ((pf + S.One)*airyai(newarg) - (pf - S.One)/sqrt(3)*airybi(newarg))
|
1486 |
+
|
1487 |
+
|
1488 |
+
class airybi(AiryBase):
|
1489 |
+
r"""
|
1490 |
+
The Airy function $\operatorname{Bi}$ of the second kind.
|
1491 |
+
|
1492 |
+
Explanation
|
1493 |
+
===========
|
1494 |
+
|
1495 |
+
The Airy function $\operatorname{Bi}(z)$ is defined to be the function
|
1496 |
+
satisfying Airy's differential equation
|
1497 |
+
|
1498 |
+
.. math::
|
1499 |
+
\frac{\mathrm{d}^2 w(z)}{\mathrm{d}z^2} - z w(z) = 0.
|
1500 |
+
|
1501 |
+
Equivalently, for real $z$
|
1502 |
+
|
1503 |
+
.. math::
|
1504 |
+
\operatorname{Bi}(z) := \frac{1}{\pi}
|
1505 |
+
\int_0^\infty
|
1506 |
+
\exp\left(-\frac{t^3}{3} + z t\right)
|
1507 |
+
+ \sin\left(\frac{t^3}{3} + z t\right) \mathrm{d}t.
|
1508 |
+
|
1509 |
+
Examples
|
1510 |
+
========
|
1511 |
+
|
1512 |
+
Create an Airy function object:
|
1513 |
+
|
1514 |
+
>>> from sympy import airybi
|
1515 |
+
>>> from sympy.abc import z
|
1516 |
+
|
1517 |
+
>>> airybi(z)
|
1518 |
+
airybi(z)
|
1519 |
+
|
1520 |
+
Several special values are known:
|
1521 |
+
|
1522 |
+
>>> airybi(0)
|
1523 |
+
3**(5/6)/(3*gamma(2/3))
|
1524 |
+
>>> from sympy import oo
|
1525 |
+
>>> airybi(oo)
|
1526 |
+
oo
|
1527 |
+
>>> airybi(-oo)
|
1528 |
+
0
|
1529 |
+
|
1530 |
+
The Airy function obeys the mirror symmetry:
|
1531 |
+
|
1532 |
+
>>> from sympy import conjugate
|
1533 |
+
>>> conjugate(airybi(z))
|
1534 |
+
airybi(conjugate(z))
|
1535 |
+
|
1536 |
+
Differentiation with respect to $z$ is supported:
|
1537 |
+
|
1538 |
+
>>> from sympy import diff
|
1539 |
+
>>> diff(airybi(z), z)
|
1540 |
+
airybiprime(z)
|
1541 |
+
>>> diff(airybi(z), z, 2)
|
1542 |
+
z*airybi(z)
|
1543 |
+
|
1544 |
+
Series expansion is also supported:
|
1545 |
+
|
1546 |
+
>>> from sympy import series
|
1547 |
+
>>> series(airybi(z), z, 0, 3)
|
1548 |
+
3**(1/3)*gamma(1/3)/(2*pi) + 3**(2/3)*z*gamma(2/3)/(2*pi) + O(z**3)
|
1549 |
+
|
1550 |
+
We can numerically evaluate the Airy function to arbitrary precision
|
1551 |
+
on the whole complex plane:
|
1552 |
+
|
1553 |
+
>>> airybi(-2).evalf(50)
|
1554 |
+
-0.41230258795639848808323405461146104203453483447240
|
1555 |
+
|
1556 |
+
Rewrite $\operatorname{Bi}(z)$ in terms of hypergeometric functions:
|
1557 |
+
|
1558 |
+
>>> from sympy import hyper
|
1559 |
+
>>> airybi(z).rewrite(hyper)
|
1560 |
+
3**(1/6)*z*hyper((), (4/3,), z**3/9)/gamma(1/3) + 3**(5/6)*hyper((), (2/3,), z**3/9)/(3*gamma(2/3))
|
1561 |
+
|
1562 |
+
See Also
|
1563 |
+
========
|
1564 |
+
|
1565 |
+
airyai: Airy function of the first kind.
|
1566 |
+
airyaiprime: Derivative of the Airy function of the first kind.
|
1567 |
+
airybiprime: Derivative of the Airy function of the second kind.
|
1568 |
+
|
1569 |
+
References
|
1570 |
+
==========
|
1571 |
+
|
1572 |
+
.. [1] https://en.wikipedia.org/wiki/Airy_function
|
1573 |
+
.. [2] https://dlmf.nist.gov/9
|
1574 |
+
.. [3] https://encyclopediaofmath.org/wiki/Airy_functions
|
1575 |
+
.. [4] https://mathworld.wolfram.com/AiryFunctions.html
|
1576 |
+
|
1577 |
+
"""
|
1578 |
+
|
1579 |
+
nargs = 1
|
1580 |
+
unbranched = True
|
1581 |
+
|
1582 |
+
@classmethod
|
1583 |
+
def eval(cls, arg):
|
1584 |
+
if arg.is_Number:
|
1585 |
+
if arg is S.NaN:
|
1586 |
+
return S.NaN
|
1587 |
+
elif arg is S.Infinity:
|
1588 |
+
return S.Infinity
|
1589 |
+
elif arg is S.NegativeInfinity:
|
1590 |
+
return S.Zero
|
1591 |
+
elif arg.is_zero:
|
1592 |
+
return S.One / (3**Rational(1, 6) * gamma(Rational(2, 3)))
|
1593 |
+
|
1594 |
+
if arg.is_zero:
|
1595 |
+
return S.One / (3**Rational(1, 6) * gamma(Rational(2, 3)))
|
1596 |
+
|
1597 |
+
def fdiff(self, argindex=1):
|
1598 |
+
if argindex == 1:
|
1599 |
+
return airybiprime(self.args[0])
|
1600 |
+
else:
|
1601 |
+
raise ArgumentIndexError(self, argindex)
|
1602 |
+
|
1603 |
+
@staticmethod
|
1604 |
+
@cacheit
|
1605 |
+
def taylor_term(n, x, *previous_terms):
|
1606 |
+
if n < 0:
|
1607 |
+
return S.Zero
|
1608 |
+
else:
|
1609 |
+
x = sympify(x)
|
1610 |
+
if len(previous_terms) > 1:
|
1611 |
+
p = previous_terms[-1]
|
1612 |
+
return (cbrt(3)*x * Abs(sin(Rational(2, 3)*pi*(n + S.One))) * factorial((n - S.One)/S(3)) /
|
1613 |
+
((n + S.One) * Abs(cos(Rational(2, 3)*pi*(n + S.Half))) * factorial((n - 2)/S(3))) * p)
|
1614 |
+
else:
|
1615 |
+
return (S.One/(root(3, 6)*pi) * gamma((n + S.One)/S(3)) * Abs(sin(Rational(2, 3)*pi*(n + S.One))) /
|
1616 |
+
factorial(n) * (cbrt(3)*x)**n)
|
1617 |
+
|
1618 |
+
def _eval_rewrite_as_besselj(self, z, **kwargs):
|
1619 |
+
ot = Rational(1, 3)
|
1620 |
+
tt = Rational(2, 3)
|
1621 |
+
a = Pow(-z, Rational(3, 2))
|
1622 |
+
if re(z).is_negative:
|
1623 |
+
return sqrt(-z/3) * (besselj(-ot, tt*a) - besselj(ot, tt*a))
|
1624 |
+
|
1625 |
+
def _eval_rewrite_as_besseli(self, z, **kwargs):
|
1626 |
+
ot = Rational(1, 3)
|
1627 |
+
tt = Rational(2, 3)
|
1628 |
+
a = Pow(z, Rational(3, 2))
|
1629 |
+
if re(z).is_positive:
|
1630 |
+
return sqrt(z)/sqrt(3) * (besseli(-ot, tt*a) + besseli(ot, tt*a))
|
1631 |
+
else:
|
1632 |
+
b = Pow(a, ot)
|
1633 |
+
c = Pow(a, -ot)
|
1634 |
+
return sqrt(ot)*(b*besseli(-ot, tt*a) + z*c*besseli(ot, tt*a))
|
1635 |
+
|
1636 |
+
def _eval_rewrite_as_hyper(self, z, **kwargs):
|
1637 |
+
pf1 = S.One / (root(3, 6)*gamma(Rational(2, 3)))
|
1638 |
+
pf2 = z*root(3, 6) / gamma(Rational(1, 3))
|
1639 |
+
return pf1 * hyper([], [Rational(2, 3)], z**3/9) + pf2 * hyper([], [Rational(4, 3)], z**3/9)
|
1640 |
+
|
1641 |
+
def _eval_expand_func(self, **hints):
|
1642 |
+
arg = self.args[0]
|
1643 |
+
symbs = arg.free_symbols
|
1644 |
+
|
1645 |
+
if len(symbs) == 1:
|
1646 |
+
z = symbs.pop()
|
1647 |
+
c = Wild("c", exclude=[z])
|
1648 |
+
d = Wild("d", exclude=[z])
|
1649 |
+
m = Wild("m", exclude=[z])
|
1650 |
+
n = Wild("n", exclude=[z])
|
1651 |
+
M = arg.match(c*(d*z**n)**m)
|
1652 |
+
if M is not None:
|
1653 |
+
m = M[m]
|
1654 |
+
# The transformation is given by 03.06.16.0001.01
|
1655 |
+
# https://functions.wolfram.com/Bessel-TypeFunctions/AiryBi/16/01/01/0001/
|
1656 |
+
if (3*m).is_integer:
|
1657 |
+
c = M[c]
|
1658 |
+
d = M[d]
|
1659 |
+
n = M[n]
|
1660 |
+
pf = (d * z**n)**m / (d**m * z**(m*n))
|
1661 |
+
newarg = c * d**m * z**(m*n)
|
1662 |
+
return S.Half * (sqrt(3)*(S.One - pf)*airyai(newarg) + (S.One + pf)*airybi(newarg))
|
1663 |
+
|
1664 |
+
|
1665 |
+
class airyaiprime(AiryBase):
|
1666 |
+
r"""
|
1667 |
+
The derivative $\operatorname{Ai}^\prime$ of the Airy function of the first
|
1668 |
+
kind.
|
1669 |
+
|
1670 |
+
Explanation
|
1671 |
+
===========
|
1672 |
+
|
1673 |
+
The Airy function $\operatorname{Ai}^\prime(z)$ is defined to be the
|
1674 |
+
function
|
1675 |
+
|
1676 |
+
.. math::
|
1677 |
+
\operatorname{Ai}^\prime(z) := \frac{\mathrm{d} \operatorname{Ai}(z)}{\mathrm{d} z}.
|
1678 |
+
|
1679 |
+
Examples
|
1680 |
+
========
|
1681 |
+
|
1682 |
+
Create an Airy function object:
|
1683 |
+
|
1684 |
+
>>> from sympy import airyaiprime
|
1685 |
+
>>> from sympy.abc import z
|
1686 |
+
|
1687 |
+
>>> airyaiprime(z)
|
1688 |
+
airyaiprime(z)
|
1689 |
+
|
1690 |
+
Several special values are known:
|
1691 |
+
|
1692 |
+
>>> airyaiprime(0)
|
1693 |
+
-3**(2/3)/(3*gamma(1/3))
|
1694 |
+
>>> from sympy import oo
|
1695 |
+
>>> airyaiprime(oo)
|
1696 |
+
0
|
1697 |
+
|
1698 |
+
The Airy function obeys the mirror symmetry:
|
1699 |
+
|
1700 |
+
>>> from sympy import conjugate
|
1701 |
+
>>> conjugate(airyaiprime(z))
|
1702 |
+
airyaiprime(conjugate(z))
|
1703 |
+
|
1704 |
+
Differentiation with respect to $z$ is supported:
|
1705 |
+
|
1706 |
+
>>> from sympy import diff
|
1707 |
+
>>> diff(airyaiprime(z), z)
|
1708 |
+
z*airyai(z)
|
1709 |
+
>>> diff(airyaiprime(z), z, 2)
|
1710 |
+
z*airyaiprime(z) + airyai(z)
|
1711 |
+
|
1712 |
+
Series expansion is also supported:
|
1713 |
+
|
1714 |
+
>>> from sympy import series
|
1715 |
+
>>> series(airyaiprime(z), z, 0, 3)
|
1716 |
+
-3**(2/3)/(3*gamma(1/3)) + 3**(1/3)*z**2/(6*gamma(2/3)) + O(z**3)
|
1717 |
+
|
1718 |
+
We can numerically evaluate the Airy function to arbitrary precision
|
1719 |
+
on the whole complex plane:
|
1720 |
+
|
1721 |
+
>>> airyaiprime(-2).evalf(50)
|
1722 |
+
0.61825902074169104140626429133247528291577794512415
|
1723 |
+
|
1724 |
+
Rewrite $\operatorname{Ai}^\prime(z)$ in terms of hypergeometric functions:
|
1725 |
+
|
1726 |
+
>>> from sympy import hyper
|
1727 |
+
>>> airyaiprime(z).rewrite(hyper)
|
1728 |
+
3**(1/3)*z**2*hyper((), (5/3,), z**3/9)/(6*gamma(2/3)) - 3**(2/3)*hyper((), (1/3,), z**3/9)/(3*gamma(1/3))
|
1729 |
+
|
1730 |
+
See Also
|
1731 |
+
========
|
1732 |
+
|
1733 |
+
airyai: Airy function of the first kind.
|
1734 |
+
airybi: Airy function of the second kind.
|
1735 |
+
airybiprime: Derivative of the Airy function of the second kind.
|
1736 |
+
|
1737 |
+
References
|
1738 |
+
==========
|
1739 |
+
|
1740 |
+
.. [1] https://en.wikipedia.org/wiki/Airy_function
|
1741 |
+
.. [2] https://dlmf.nist.gov/9
|
1742 |
+
.. [3] https://encyclopediaofmath.org/wiki/Airy_functions
|
1743 |
+
.. [4] https://mathworld.wolfram.com/AiryFunctions.html
|
1744 |
+
|
1745 |
+
"""
|
1746 |
+
|
1747 |
+
nargs = 1
|
1748 |
+
unbranched = True
|
1749 |
+
|
1750 |
+
@classmethod
|
1751 |
+
def eval(cls, arg):
|
1752 |
+
if arg.is_Number:
|
1753 |
+
if arg is S.NaN:
|
1754 |
+
return S.NaN
|
1755 |
+
elif arg is S.Infinity:
|
1756 |
+
return S.Zero
|
1757 |
+
|
1758 |
+
if arg.is_zero:
|
1759 |
+
return S.NegativeOne / (3**Rational(1, 3) * gamma(Rational(1, 3)))
|
1760 |
+
|
1761 |
+
def fdiff(self, argindex=1):
|
1762 |
+
if argindex == 1:
|
1763 |
+
return self.args[0]*airyai(self.args[0])
|
1764 |
+
else:
|
1765 |
+
raise ArgumentIndexError(self, argindex)
|
1766 |
+
|
1767 |
+
def _eval_evalf(self, prec):
|
1768 |
+
z = self.args[0]._to_mpmath(prec)
|
1769 |
+
with workprec(prec):
|
1770 |
+
res = mp.airyai(z, derivative=1)
|
1771 |
+
return Expr._from_mpmath(res, prec)
|
1772 |
+
|
1773 |
+
def _eval_rewrite_as_besselj(self, z, **kwargs):
|
1774 |
+
tt = Rational(2, 3)
|
1775 |
+
a = Pow(-z, Rational(3, 2))
|
1776 |
+
if re(z).is_negative:
|
1777 |
+
return z/3 * (besselj(-tt, tt*a) - besselj(tt, tt*a))
|
1778 |
+
|
1779 |
+
def _eval_rewrite_as_besseli(self, z, **kwargs):
|
1780 |
+
ot = Rational(1, 3)
|
1781 |
+
tt = Rational(2, 3)
|
1782 |
+
a = tt * Pow(z, Rational(3, 2))
|
1783 |
+
if re(z).is_positive:
|
1784 |
+
return z/3 * (besseli(tt, a) - besseli(-tt, a))
|
1785 |
+
else:
|
1786 |
+
a = Pow(z, Rational(3, 2))
|
1787 |
+
b = Pow(a, tt)
|
1788 |
+
c = Pow(a, -tt)
|
1789 |
+
return ot * (z**2*c*besseli(tt, tt*a) - b*besseli(-ot, tt*a))
|
1790 |
+
|
1791 |
+
def _eval_rewrite_as_hyper(self, z, **kwargs):
|
1792 |
+
pf1 = z**2 / (2*3**Rational(2, 3)*gamma(Rational(2, 3)))
|
1793 |
+
pf2 = 1 / (root(3, 3)*gamma(Rational(1, 3)))
|
1794 |
+
return pf1 * hyper([], [Rational(5, 3)], z**3/9) - pf2 * hyper([], [Rational(1, 3)], z**3/9)
|
1795 |
+
|
1796 |
+
def _eval_expand_func(self, **hints):
|
1797 |
+
arg = self.args[0]
|
1798 |
+
symbs = arg.free_symbols
|
1799 |
+
|
1800 |
+
if len(symbs) == 1:
|
1801 |
+
z = symbs.pop()
|
1802 |
+
c = Wild("c", exclude=[z])
|
1803 |
+
d = Wild("d", exclude=[z])
|
1804 |
+
m = Wild("m", exclude=[z])
|
1805 |
+
n = Wild("n", exclude=[z])
|
1806 |
+
M = arg.match(c*(d*z**n)**m)
|
1807 |
+
if M is not None:
|
1808 |
+
m = M[m]
|
1809 |
+
# The transformation is in principle
|
1810 |
+
# given by 03.07.16.0001.01 but note
|
1811 |
+
# that there is an error in this formula.
|
1812 |
+
# https://functions.wolfram.com/Bessel-TypeFunctions/AiryAiPrime/16/01/01/0001/
|
1813 |
+
if (3*m).is_integer:
|
1814 |
+
c = M[c]
|
1815 |
+
d = M[d]
|
1816 |
+
n = M[n]
|
1817 |
+
pf = (d**m * z**(n*m)) / (d * z**n)**m
|
1818 |
+
newarg = c * d**m * z**(n*m)
|
1819 |
+
return S.Half * ((pf + S.One)*airyaiprime(newarg) + (pf - S.One)/sqrt(3)*airybiprime(newarg))
|
1820 |
+
|
1821 |
+
|
1822 |
+
class airybiprime(AiryBase):
|
1823 |
+
r"""
|
1824 |
+
The derivative $\operatorname{Bi}^\prime$ of the Airy function of the first
|
1825 |
+
kind.
|
1826 |
+
|
1827 |
+
Explanation
|
1828 |
+
===========
|
1829 |
+
|
1830 |
+
The Airy function $\operatorname{Bi}^\prime(z)$ is defined to be the
|
1831 |
+
function
|
1832 |
+
|
1833 |
+
.. math::
|
1834 |
+
\operatorname{Bi}^\prime(z) := \frac{\mathrm{d} \operatorname{Bi}(z)}{\mathrm{d} z}.
|
1835 |
+
|
1836 |
+
Examples
|
1837 |
+
========
|
1838 |
+
|
1839 |
+
Create an Airy function object:
|
1840 |
+
|
1841 |
+
>>> from sympy import airybiprime
|
1842 |
+
>>> from sympy.abc import z
|
1843 |
+
|
1844 |
+
>>> airybiprime(z)
|
1845 |
+
airybiprime(z)
|
1846 |
+
|
1847 |
+
Several special values are known:
|
1848 |
+
|
1849 |
+
>>> airybiprime(0)
|
1850 |
+
3**(1/6)/gamma(1/3)
|
1851 |
+
>>> from sympy import oo
|
1852 |
+
>>> airybiprime(oo)
|
1853 |
+
oo
|
1854 |
+
>>> airybiprime(-oo)
|
1855 |
+
0
|
1856 |
+
|
1857 |
+
The Airy function obeys the mirror symmetry:
|
1858 |
+
|
1859 |
+
>>> from sympy import conjugate
|
1860 |
+
>>> conjugate(airybiprime(z))
|
1861 |
+
airybiprime(conjugate(z))
|
1862 |
+
|
1863 |
+
Differentiation with respect to $z$ is supported:
|
1864 |
+
|
1865 |
+
>>> from sympy import diff
|
1866 |
+
>>> diff(airybiprime(z), z)
|
1867 |
+
z*airybi(z)
|
1868 |
+
>>> diff(airybiprime(z), z, 2)
|
1869 |
+
z*airybiprime(z) + airybi(z)
|
1870 |
+
|
1871 |
+
Series expansion is also supported:
|
1872 |
+
|
1873 |
+
>>> from sympy import series
|
1874 |
+
>>> series(airybiprime(z), z, 0, 3)
|
1875 |
+
3**(1/6)/gamma(1/3) + 3**(5/6)*z**2/(6*gamma(2/3)) + O(z**3)
|
1876 |
+
|
1877 |
+
We can numerically evaluate the Airy function to arbitrary precision
|
1878 |
+
on the whole complex plane:
|
1879 |
+
|
1880 |
+
>>> airybiprime(-2).evalf(50)
|
1881 |
+
0.27879516692116952268509756941098324140300059345163
|
1882 |
+
|
1883 |
+
Rewrite $\operatorname{Bi}^\prime(z)$ in terms of hypergeometric functions:
|
1884 |
+
|
1885 |
+
>>> from sympy import hyper
|
1886 |
+
>>> airybiprime(z).rewrite(hyper)
|
1887 |
+
3**(5/6)*z**2*hyper((), (5/3,), z**3/9)/(6*gamma(2/3)) + 3**(1/6)*hyper((), (1/3,), z**3/9)/gamma(1/3)
|
1888 |
+
|
1889 |
+
See Also
|
1890 |
+
========
|
1891 |
+
|
1892 |
+
airyai: Airy function of the first kind.
|
1893 |
+
airybi: Airy function of the second kind.
|
1894 |
+
airyaiprime: Derivative of the Airy function of the first kind.
|
1895 |
+
|
1896 |
+
References
|
1897 |
+
==========
|
1898 |
+
|
1899 |
+
.. [1] https://en.wikipedia.org/wiki/Airy_function
|
1900 |
+
.. [2] https://dlmf.nist.gov/9
|
1901 |
+
.. [3] https://encyclopediaofmath.org/wiki/Airy_functions
|
1902 |
+
.. [4] https://mathworld.wolfram.com/AiryFunctions.html
|
1903 |
+
|
1904 |
+
"""
|
1905 |
+
|
1906 |
+
nargs = 1
|
1907 |
+
unbranched = True
|
1908 |
+
|
1909 |
+
@classmethod
|
1910 |
+
def eval(cls, arg):
|
1911 |
+
if arg.is_Number:
|
1912 |
+
if arg is S.NaN:
|
1913 |
+
return S.NaN
|
1914 |
+
elif arg is S.Infinity:
|
1915 |
+
return S.Infinity
|
1916 |
+
elif arg is S.NegativeInfinity:
|
1917 |
+
return S.Zero
|
1918 |
+
elif arg.is_zero:
|
1919 |
+
return 3**Rational(1, 6) / gamma(Rational(1, 3))
|
1920 |
+
|
1921 |
+
if arg.is_zero:
|
1922 |
+
return 3**Rational(1, 6) / gamma(Rational(1, 3))
|
1923 |
+
|
1924 |
+
|
1925 |
+
def fdiff(self, argindex=1):
|
1926 |
+
if argindex == 1:
|
1927 |
+
return self.args[0]*airybi(self.args[0])
|
1928 |
+
else:
|
1929 |
+
raise ArgumentIndexError(self, argindex)
|
1930 |
+
|
1931 |
+
def _eval_evalf(self, prec):
|
1932 |
+
z = self.args[0]._to_mpmath(prec)
|
1933 |
+
with workprec(prec):
|
1934 |
+
res = mp.airybi(z, derivative=1)
|
1935 |
+
return Expr._from_mpmath(res, prec)
|
1936 |
+
|
1937 |
+
def _eval_rewrite_as_besselj(self, z, **kwargs):
|
1938 |
+
tt = Rational(2, 3)
|
1939 |
+
a = tt * Pow(-z, Rational(3, 2))
|
1940 |
+
if re(z).is_negative:
|
1941 |
+
return -z/sqrt(3) * (besselj(-tt, a) + besselj(tt, a))
|
1942 |
+
|
1943 |
+
def _eval_rewrite_as_besseli(self, z, **kwargs):
|
1944 |
+
ot = Rational(1, 3)
|
1945 |
+
tt = Rational(2, 3)
|
1946 |
+
a = tt * Pow(z, Rational(3, 2))
|
1947 |
+
if re(z).is_positive:
|
1948 |
+
return z/sqrt(3) * (besseli(-tt, a) + besseli(tt, a))
|
1949 |
+
else:
|
1950 |
+
a = Pow(z, Rational(3, 2))
|
1951 |
+
b = Pow(a, tt)
|
1952 |
+
c = Pow(a, -tt)
|
1953 |
+
return sqrt(ot) * (b*besseli(-tt, tt*a) + z**2*c*besseli(tt, tt*a))
|
1954 |
+
|
1955 |
+
def _eval_rewrite_as_hyper(self, z, **kwargs):
|
1956 |
+
pf1 = z**2 / (2*root(3, 6)*gamma(Rational(2, 3)))
|
1957 |
+
pf2 = root(3, 6) / gamma(Rational(1, 3))
|
1958 |
+
return pf1 * hyper([], [Rational(5, 3)], z**3/9) + pf2 * hyper([], [Rational(1, 3)], z**3/9)
|
1959 |
+
|
1960 |
+
def _eval_expand_func(self, **hints):
|
1961 |
+
arg = self.args[0]
|
1962 |
+
symbs = arg.free_symbols
|
1963 |
+
|
1964 |
+
if len(symbs) == 1:
|
1965 |
+
z = symbs.pop()
|
1966 |
+
c = Wild("c", exclude=[z])
|
1967 |
+
d = Wild("d", exclude=[z])
|
1968 |
+
m = Wild("m", exclude=[z])
|
1969 |
+
n = Wild("n", exclude=[z])
|
1970 |
+
M = arg.match(c*(d*z**n)**m)
|
1971 |
+
if M is not None:
|
1972 |
+
m = M[m]
|
1973 |
+
# The transformation is in principle
|
1974 |
+
# given by 03.08.16.0001.01 but note
|
1975 |
+
# that there is an error in this formula.
|
1976 |
+
# https://functions.wolfram.com/Bessel-TypeFunctions/AiryBiPrime/16/01/01/0001/
|
1977 |
+
if (3*m).is_integer:
|
1978 |
+
c = M[c]
|
1979 |
+
d = M[d]
|
1980 |
+
n = M[n]
|
1981 |
+
pf = (d**m * z**(n*m)) / (d * z**n)**m
|
1982 |
+
newarg = c * d**m * z**(n*m)
|
1983 |
+
return S.Half * (sqrt(3)*(pf - S.One)*airyaiprime(newarg) + (pf + S.One)*airybiprime(newarg))
|
1984 |
+
|
1985 |
+
|
1986 |
+
class marcumq(Function):
|
1987 |
+
r"""
|
1988 |
+
The Marcum Q-function.
|
1989 |
+
|
1990 |
+
Explanation
|
1991 |
+
===========
|
1992 |
+
|
1993 |
+
The Marcum Q-function is defined by the meromorphic continuation of
|
1994 |
+
|
1995 |
+
.. math::
|
1996 |
+
Q_m(a, b) = a^{- m + 1} \int_{b}^{\infty} x^{m} e^{- \frac{a^{2}}{2} - \frac{x^{2}}{2}} I_{m - 1}\left(a x\right)\, dx
|
1997 |
+
|
1998 |
+
Examples
|
1999 |
+
========
|
2000 |
+
|
2001 |
+
>>> from sympy import marcumq
|
2002 |
+
>>> from sympy.abc import m, a, b
|
2003 |
+
>>> marcumq(m, a, b)
|
2004 |
+
marcumq(m, a, b)
|
2005 |
+
|
2006 |
+
Special values:
|
2007 |
+
|
2008 |
+
>>> marcumq(m, 0, b)
|
2009 |
+
uppergamma(m, b**2/2)/gamma(m)
|
2010 |
+
>>> marcumq(0, 0, 0)
|
2011 |
+
0
|
2012 |
+
>>> marcumq(0, a, 0)
|
2013 |
+
1 - exp(-a**2/2)
|
2014 |
+
>>> marcumq(1, a, a)
|
2015 |
+
1/2 + exp(-a**2)*besseli(0, a**2)/2
|
2016 |
+
>>> marcumq(2, a, a)
|
2017 |
+
1/2 + exp(-a**2)*besseli(0, a**2)/2 + exp(-a**2)*besseli(1, a**2)
|
2018 |
+
|
2019 |
+
Differentiation with respect to $a$ and $b$ is supported:
|
2020 |
+
|
2021 |
+
>>> from sympy import diff
|
2022 |
+
>>> diff(marcumq(m, a, b), a)
|
2023 |
+
a*(-marcumq(m, a, b) + marcumq(m + 1, a, b))
|
2024 |
+
>>> diff(marcumq(m, a, b), b)
|
2025 |
+
-a**(1 - m)*b**m*exp(-a**2/2 - b**2/2)*besseli(m - 1, a*b)
|
2026 |
+
|
2027 |
+
References
|
2028 |
+
==========
|
2029 |
+
|
2030 |
+
.. [1] https://en.wikipedia.org/wiki/Marcum_Q-function
|
2031 |
+
.. [2] https://mathworld.wolfram.com/MarcumQ-Function.html
|
2032 |
+
|
2033 |
+
"""
|
2034 |
+
|
2035 |
+
@classmethod
|
2036 |
+
def eval(cls, m, a, b):
|
2037 |
+
if a is S.Zero:
|
2038 |
+
if m is S.Zero and b is S.Zero:
|
2039 |
+
return S.Zero
|
2040 |
+
return uppergamma(m, b**2 * S.Half) / gamma(m)
|
2041 |
+
|
2042 |
+
if m is S.Zero and b is S.Zero:
|
2043 |
+
return 1 - 1 / exp(a**2 * S.Half)
|
2044 |
+
|
2045 |
+
if a == b:
|
2046 |
+
if m is S.One:
|
2047 |
+
return (1 + exp(-a**2) * besseli(0, a**2))*S.Half
|
2048 |
+
if m == 2:
|
2049 |
+
return S.Half + S.Half * exp(-a**2) * besseli(0, a**2) + exp(-a**2) * besseli(1, a**2)
|
2050 |
+
|
2051 |
+
if a.is_zero:
|
2052 |
+
if m.is_zero and b.is_zero:
|
2053 |
+
return S.Zero
|
2054 |
+
return uppergamma(m, b**2*S.Half) / gamma(m)
|
2055 |
+
|
2056 |
+
if m.is_zero and b.is_zero:
|
2057 |
+
return 1 - 1 / exp(a**2*S.Half)
|
2058 |
+
|
2059 |
+
def fdiff(self, argindex=2):
|
2060 |
+
m, a, b = self.args
|
2061 |
+
if argindex == 2:
|
2062 |
+
return a * (-marcumq(m, a, b) + marcumq(1+m, a, b))
|
2063 |
+
elif argindex == 3:
|
2064 |
+
return (-b**m / a**(m-1)) * exp(-(a**2 + b**2)/2) * besseli(m-1, a*b)
|
2065 |
+
else:
|
2066 |
+
raise ArgumentIndexError(self, argindex)
|
2067 |
+
|
2068 |
+
def _eval_rewrite_as_Integral(self, m, a, b, **kwargs):
|
2069 |
+
from sympy.integrals.integrals import Integral
|
2070 |
+
x = kwargs.get('x', Dummy('x'))
|
2071 |
+
return a ** (1 - m) * \
|
2072 |
+
Integral(x**m * exp(-(x**2 + a**2)/2) * besseli(m-1, a*x), [x, b, S.Infinity])
|
2073 |
+
|
2074 |
+
def _eval_rewrite_as_Sum(self, m, a, b, **kwargs):
|
2075 |
+
from sympy.concrete.summations import Sum
|
2076 |
+
k = kwargs.get('k', Dummy('k'))
|
2077 |
+
return exp(-(a**2 + b**2) / 2) * Sum((a/b)**k * besseli(k, a*b), [k, 1-m, S.Infinity])
|
2078 |
+
|
2079 |
+
def _eval_rewrite_as_besseli(self, m, a, b, **kwargs):
|
2080 |
+
if a == b:
|
2081 |
+
if m == 1:
|
2082 |
+
return (1 + exp(-a**2) * besseli(0, a**2)) / 2
|
2083 |
+
if m.is_Integer and m >= 2:
|
2084 |
+
s = sum([besseli(i, a**2) for i in range(1, m)])
|
2085 |
+
return S.Half + exp(-a**2) * besseli(0, a**2) / 2 + exp(-a**2) * s
|
2086 |
+
|
2087 |
+
def _eval_is_zero(self):
|
2088 |
+
if all(arg.is_zero for arg in self.args):
|
2089 |
+
return True
|
venv/lib/python3.10/site-packages/sympy/functions/special/beta_functions.py
ADDED
@@ -0,0 +1,389 @@
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|
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|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
1 |
+
from sympy.core import S
|
2 |
+
from sympy.core.function import Function, ArgumentIndexError
|
3 |
+
from sympy.core.symbol import Dummy
|
4 |
+
from sympy.functions.special.gamma_functions import gamma, digamma
|
5 |
+
from sympy.functions.combinatorial.numbers import catalan
|
6 |
+
from sympy.functions.elementary.complexes import conjugate
|
7 |
+
|
8 |
+
# See mpmath #569 and SymPy #20569
|
9 |
+
def betainc_mpmath_fix(a, b, x1, x2, reg=0):
|
10 |
+
from mpmath import betainc, mpf
|
11 |
+
if x1 == x2:
|
12 |
+
return mpf(0)
|
13 |
+
else:
|
14 |
+
return betainc(a, b, x1, x2, reg)
|
15 |
+
|
16 |
+
###############################################################################
|
17 |
+
############################ COMPLETE BETA FUNCTION ##########################
|
18 |
+
###############################################################################
|
19 |
+
|
20 |
+
class beta(Function):
|
21 |
+
r"""
|
22 |
+
The beta integral is called the Eulerian integral of the first kind by
|
23 |
+
Legendre:
|
24 |
+
|
25 |
+
.. math::
|
26 |
+
\mathrm{B}(x,y) \int^{1}_{0} t^{x-1} (1-t)^{y-1} \mathrm{d}t.
|
27 |
+
|
28 |
+
Explanation
|
29 |
+
===========
|
30 |
+
|
31 |
+
The Beta function or Euler's first integral is closely associated
|
32 |
+
with the gamma function. The Beta function is often used in probability
|
33 |
+
theory and mathematical statistics. It satisfies properties like:
|
34 |
+
|
35 |
+
.. math::
|
36 |
+
\mathrm{B}(a,1) = \frac{1}{a} \\
|
37 |
+
\mathrm{B}(a,b) = \mathrm{B}(b,a) \\
|
38 |
+
\mathrm{B}(a,b) = \frac{\Gamma(a) \Gamma(b)}{\Gamma(a+b)}
|
39 |
+
|
40 |
+
Therefore for integral values of $a$ and $b$:
|
41 |
+
|
42 |
+
.. math::
|
43 |
+
\mathrm{B} = \frac{(a-1)! (b-1)!}{(a+b-1)!}
|
44 |
+
|
45 |
+
A special case of the Beta function when `x = y` is the
|
46 |
+
Central Beta function. It satisfies properties like:
|
47 |
+
|
48 |
+
.. math::
|
49 |
+
\mathrm{B}(x) = 2^{1 - 2x}\mathrm{B}(x, \frac{1}{2})
|
50 |
+
\mathrm{B}(x) = 2^{1 - 2x} cos(\pi x) \mathrm{B}(\frac{1}{2} - x, x)
|
51 |
+
\mathrm{B}(x) = \int_{0}^{1} \frac{t^x}{(1 + t)^{2x}} dt
|
52 |
+
\mathrm{B}(x) = \frac{2}{x} \prod_{n = 1}^{\infty} \frac{n(n + 2x)}{(n + x)^2}
|
53 |
+
|
54 |
+
Examples
|
55 |
+
========
|
56 |
+
|
57 |
+
>>> from sympy import I, pi
|
58 |
+
>>> from sympy.abc import x, y
|
59 |
+
|
60 |
+
The Beta function obeys the mirror symmetry:
|
61 |
+
|
62 |
+
>>> from sympy import beta, conjugate
|
63 |
+
>>> conjugate(beta(x, y))
|
64 |
+
beta(conjugate(x), conjugate(y))
|
65 |
+
|
66 |
+
Differentiation with respect to both $x$ and $y$ is supported:
|
67 |
+
|
68 |
+
>>> from sympy import beta, diff
|
69 |
+
>>> diff(beta(x, y), x)
|
70 |
+
(polygamma(0, x) - polygamma(0, x + y))*beta(x, y)
|
71 |
+
|
72 |
+
>>> diff(beta(x, y), y)
|
73 |
+
(polygamma(0, y) - polygamma(0, x + y))*beta(x, y)
|
74 |
+
|
75 |
+
>>> diff(beta(x), x)
|
76 |
+
2*(polygamma(0, x) - polygamma(0, 2*x))*beta(x, x)
|
77 |
+
|
78 |
+
We can numerically evaluate the Beta function to
|
79 |
+
arbitrary precision for any complex numbers x and y:
|
80 |
+
|
81 |
+
>>> from sympy import beta
|
82 |
+
>>> beta(pi).evalf(40)
|
83 |
+
0.02671848900111377452242355235388489324562
|
84 |
+
|
85 |
+
>>> beta(1 + I).evalf(20)
|
86 |
+
-0.2112723729365330143 - 0.7655283165378005676*I
|
87 |
+
|
88 |
+
See Also
|
89 |
+
========
|
90 |
+
|
91 |
+
gamma: Gamma function.
|
92 |
+
uppergamma: Upper incomplete gamma function.
|
93 |
+
lowergamma: Lower incomplete gamma function.
|
94 |
+
polygamma: Polygamma function.
|
95 |
+
loggamma: Log Gamma function.
|
96 |
+
digamma: Digamma function.
|
97 |
+
trigamma: Trigamma function.
|
98 |
+
|
99 |
+
References
|
100 |
+
==========
|
101 |
+
|
102 |
+
.. [1] https://en.wikipedia.org/wiki/Beta_function
|
103 |
+
.. [2] https://mathworld.wolfram.com/BetaFunction.html
|
104 |
+
.. [3] https://dlmf.nist.gov/5.12
|
105 |
+
|
106 |
+
"""
|
107 |
+
unbranched = True
|
108 |
+
|
109 |
+
def fdiff(self, argindex):
|
110 |
+
x, y = self.args
|
111 |
+
if argindex == 1:
|
112 |
+
# Diff wrt x
|
113 |
+
return beta(x, y)*(digamma(x) - digamma(x + y))
|
114 |
+
elif argindex == 2:
|
115 |
+
# Diff wrt y
|
116 |
+
return beta(x, y)*(digamma(y) - digamma(x + y))
|
117 |
+
else:
|
118 |
+
raise ArgumentIndexError(self, argindex)
|
119 |
+
|
120 |
+
@classmethod
|
121 |
+
def eval(cls, x, y=None):
|
122 |
+
if y is None:
|
123 |
+
return beta(x, x)
|
124 |
+
if x.is_Number and y.is_Number:
|
125 |
+
return beta(x, y, evaluate=False).doit()
|
126 |
+
|
127 |
+
def doit(self, **hints):
|
128 |
+
x = xold = self.args[0]
|
129 |
+
# Deal with unevaluated single argument beta
|
130 |
+
single_argument = len(self.args) == 1
|
131 |
+
y = yold = self.args[0] if single_argument else self.args[1]
|
132 |
+
if hints.get('deep', True):
|
133 |
+
x = x.doit(**hints)
|
134 |
+
y = y.doit(**hints)
|
135 |
+
if y.is_zero or x.is_zero:
|
136 |
+
return S.ComplexInfinity
|
137 |
+
if y is S.One:
|
138 |
+
return 1/x
|
139 |
+
if x is S.One:
|
140 |
+
return 1/y
|
141 |
+
if y == x + 1:
|
142 |
+
return 1/(x*y*catalan(x))
|
143 |
+
s = x + y
|
144 |
+
if (s.is_integer and s.is_negative and x.is_integer is False and
|
145 |
+
y.is_integer is False):
|
146 |
+
return S.Zero
|
147 |
+
if x == xold and y == yold and not single_argument:
|
148 |
+
return self
|
149 |
+
return beta(x, y)
|
150 |
+
|
151 |
+
def _eval_expand_func(self, **hints):
|
152 |
+
x, y = self.args
|
153 |
+
return gamma(x)*gamma(y) / gamma(x + y)
|
154 |
+
|
155 |
+
def _eval_is_real(self):
|
156 |
+
return self.args[0].is_real and self.args[1].is_real
|
157 |
+
|
158 |
+
def _eval_conjugate(self):
|
159 |
+
return self.func(self.args[0].conjugate(), self.args[1].conjugate())
|
160 |
+
|
161 |
+
def _eval_rewrite_as_gamma(self, x, y, piecewise=True, **kwargs):
|
162 |
+
return self._eval_expand_func(**kwargs)
|
163 |
+
|
164 |
+
def _eval_rewrite_as_Integral(self, x, y, **kwargs):
|
165 |
+
from sympy.integrals.integrals import Integral
|
166 |
+
t = Dummy('t')
|
167 |
+
return Integral(t**(x - 1)*(1 - t)**(y - 1), (t, 0, 1))
|
168 |
+
|
169 |
+
###############################################################################
|
170 |
+
########################## INCOMPLETE BETA FUNCTION ###########################
|
171 |
+
###############################################################################
|
172 |
+
|
173 |
+
class betainc(Function):
|
174 |
+
r"""
|
175 |
+
The Generalized Incomplete Beta function is defined as
|
176 |
+
|
177 |
+
.. math::
|
178 |
+
\mathrm{B}_{(x_1, x_2)}(a, b) = \int_{x_1}^{x_2} t^{a - 1} (1 - t)^{b - 1} dt
|
179 |
+
|
180 |
+
The Incomplete Beta function is a special case
|
181 |
+
of the Generalized Incomplete Beta function :
|
182 |
+
|
183 |
+
.. math:: \mathrm{B}_z (a, b) = \mathrm{B}_{(0, z)}(a, b)
|
184 |
+
|
185 |
+
The Incomplete Beta function satisfies :
|
186 |
+
|
187 |
+
.. math:: \mathrm{B}_z (a, b) = (-1)^a \mathrm{B}_{\frac{z}{z - 1}} (a, 1 - a - b)
|
188 |
+
|
189 |
+
The Beta function is a special case of the Incomplete Beta function :
|
190 |
+
|
191 |
+
.. math:: \mathrm{B}(a, b) = \mathrm{B}_{1}(a, b)
|
192 |
+
|
193 |
+
Examples
|
194 |
+
========
|
195 |
+
|
196 |
+
>>> from sympy import betainc, symbols, conjugate
|
197 |
+
>>> a, b, x, x1, x2 = symbols('a b x x1 x2')
|
198 |
+
|
199 |
+
The Generalized Incomplete Beta function is given by:
|
200 |
+
|
201 |
+
>>> betainc(a, b, x1, x2)
|
202 |
+
betainc(a, b, x1, x2)
|
203 |
+
|
204 |
+
The Incomplete Beta function can be obtained as follows:
|
205 |
+
|
206 |
+
>>> betainc(a, b, 0, x)
|
207 |
+
betainc(a, b, 0, x)
|
208 |
+
|
209 |
+
The Incomplete Beta function obeys the mirror symmetry:
|
210 |
+
|
211 |
+
>>> conjugate(betainc(a, b, x1, x2))
|
212 |
+
betainc(conjugate(a), conjugate(b), conjugate(x1), conjugate(x2))
|
213 |
+
|
214 |
+
We can numerically evaluate the Incomplete Beta function to
|
215 |
+
arbitrary precision for any complex numbers a, b, x1 and x2:
|
216 |
+
|
217 |
+
>>> from sympy import betainc, I
|
218 |
+
>>> betainc(2, 3, 4, 5).evalf(10)
|
219 |
+
56.08333333
|
220 |
+
>>> betainc(0.75, 1 - 4*I, 0, 2 + 3*I).evalf(25)
|
221 |
+
0.2241657956955709603655887 + 0.3619619242700451992411724*I
|
222 |
+
|
223 |
+
The Generalized Incomplete Beta function can be expressed
|
224 |
+
in terms of the Generalized Hypergeometric function.
|
225 |
+
|
226 |
+
>>> from sympy import hyper
|
227 |
+
>>> betainc(a, b, x1, x2).rewrite(hyper)
|
228 |
+
(-x1**a*hyper((a, 1 - b), (a + 1,), x1) + x2**a*hyper((a, 1 - b), (a + 1,), x2))/a
|
229 |
+
|
230 |
+
See Also
|
231 |
+
========
|
232 |
+
|
233 |
+
beta: Beta function
|
234 |
+
hyper: Generalized Hypergeometric function
|
235 |
+
|
236 |
+
References
|
237 |
+
==========
|
238 |
+
|
239 |
+
.. [1] https://en.wikipedia.org/wiki/Beta_function#Incomplete_beta_function
|
240 |
+
.. [2] https://dlmf.nist.gov/8.17
|
241 |
+
.. [3] https://functions.wolfram.com/GammaBetaErf/Beta4/
|
242 |
+
.. [4] https://functions.wolfram.com/GammaBetaErf/BetaRegularized4/02/
|
243 |
+
|
244 |
+
"""
|
245 |
+
nargs = 4
|
246 |
+
unbranched = True
|
247 |
+
|
248 |
+
def fdiff(self, argindex):
|
249 |
+
a, b, x1, x2 = self.args
|
250 |
+
if argindex == 3:
|
251 |
+
# Diff wrt x1
|
252 |
+
return -(1 - x1)**(b - 1)*x1**(a - 1)
|
253 |
+
elif argindex == 4:
|
254 |
+
# Diff wrt x2
|
255 |
+
return (1 - x2)**(b - 1)*x2**(a - 1)
|
256 |
+
else:
|
257 |
+
raise ArgumentIndexError(self, argindex)
|
258 |
+
|
259 |
+
def _eval_mpmath(self):
|
260 |
+
return betainc_mpmath_fix, self.args
|
261 |
+
|
262 |
+
def _eval_is_real(self):
|
263 |
+
if all(arg.is_real for arg in self.args):
|
264 |
+
return True
|
265 |
+
|
266 |
+
def _eval_conjugate(self):
|
267 |
+
return self.func(*map(conjugate, self.args))
|
268 |
+
|
269 |
+
def _eval_rewrite_as_Integral(self, a, b, x1, x2, **kwargs):
|
270 |
+
from sympy.integrals.integrals import Integral
|
271 |
+
t = Dummy('t')
|
272 |
+
return Integral(t**(a - 1)*(1 - t)**(b - 1), (t, x1, x2))
|
273 |
+
|
274 |
+
def _eval_rewrite_as_hyper(self, a, b, x1, x2, **kwargs):
|
275 |
+
from sympy.functions.special.hyper import hyper
|
276 |
+
return (x2**a * hyper((a, 1 - b), (a + 1,), x2) - x1**a * hyper((a, 1 - b), (a + 1,), x1)) / a
|
277 |
+
|
278 |
+
###############################################################################
|
279 |
+
#################### REGULARIZED INCOMPLETE BETA FUNCTION #####################
|
280 |
+
###############################################################################
|
281 |
+
|
282 |
+
class betainc_regularized(Function):
|
283 |
+
r"""
|
284 |
+
The Generalized Regularized Incomplete Beta function is given by
|
285 |
+
|
286 |
+
.. math::
|
287 |
+
\mathrm{I}_{(x_1, x_2)}(a, b) = \frac{\mathrm{B}_{(x_1, x_2)}(a, b)}{\mathrm{B}(a, b)}
|
288 |
+
|
289 |
+
The Regularized Incomplete Beta function is a special case
|
290 |
+
of the Generalized Regularized Incomplete Beta function :
|
291 |
+
|
292 |
+
.. math:: \mathrm{I}_z (a, b) = \mathrm{I}_{(0, z)}(a, b)
|
293 |
+
|
294 |
+
The Regularized Incomplete Beta function is the cumulative distribution
|
295 |
+
function of the beta distribution.
|
296 |
+
|
297 |
+
Examples
|
298 |
+
========
|
299 |
+
|
300 |
+
>>> from sympy import betainc_regularized, symbols, conjugate
|
301 |
+
>>> a, b, x, x1, x2 = symbols('a b x x1 x2')
|
302 |
+
|
303 |
+
The Generalized Regularized Incomplete Beta
|
304 |
+
function is given by:
|
305 |
+
|
306 |
+
>>> betainc_regularized(a, b, x1, x2)
|
307 |
+
betainc_regularized(a, b, x1, x2)
|
308 |
+
|
309 |
+
The Regularized Incomplete Beta function
|
310 |
+
can be obtained as follows:
|
311 |
+
|
312 |
+
>>> betainc_regularized(a, b, 0, x)
|
313 |
+
betainc_regularized(a, b, 0, x)
|
314 |
+
|
315 |
+
The Regularized Incomplete Beta function
|
316 |
+
obeys the mirror symmetry:
|
317 |
+
|
318 |
+
>>> conjugate(betainc_regularized(a, b, x1, x2))
|
319 |
+
betainc_regularized(conjugate(a), conjugate(b), conjugate(x1), conjugate(x2))
|
320 |
+
|
321 |
+
We can numerically evaluate the Regularized Incomplete Beta function
|
322 |
+
to arbitrary precision for any complex numbers a, b, x1 and x2:
|
323 |
+
|
324 |
+
>>> from sympy import betainc_regularized, pi, E
|
325 |
+
>>> betainc_regularized(1, 2, 0, 0.25).evalf(10)
|
326 |
+
0.4375000000
|
327 |
+
>>> betainc_regularized(pi, E, 0, 1).evalf(5)
|
328 |
+
1.00000
|
329 |
+
|
330 |
+
The Generalized Regularized Incomplete Beta function can be
|
331 |
+
expressed in terms of the Generalized Hypergeometric function.
|
332 |
+
|
333 |
+
>>> from sympy import hyper
|
334 |
+
>>> betainc_regularized(a, b, x1, x2).rewrite(hyper)
|
335 |
+
(-x1**a*hyper((a, 1 - b), (a + 1,), x1) + x2**a*hyper((a, 1 - b), (a + 1,), x2))/(a*beta(a, b))
|
336 |
+
|
337 |
+
See Also
|
338 |
+
========
|
339 |
+
|
340 |
+
beta: Beta function
|
341 |
+
hyper: Generalized Hypergeometric function
|
342 |
+
|
343 |
+
References
|
344 |
+
==========
|
345 |
+
|
346 |
+
.. [1] https://en.wikipedia.org/wiki/Beta_function#Incomplete_beta_function
|
347 |
+
.. [2] https://dlmf.nist.gov/8.17
|
348 |
+
.. [3] https://functions.wolfram.com/GammaBetaErf/Beta4/
|
349 |
+
.. [4] https://functions.wolfram.com/GammaBetaErf/BetaRegularized4/02/
|
350 |
+
|
351 |
+
"""
|
352 |
+
nargs = 4
|
353 |
+
unbranched = True
|
354 |
+
|
355 |
+
def __new__(cls, a, b, x1, x2):
|
356 |
+
return Function.__new__(cls, a, b, x1, x2)
|
357 |
+
|
358 |
+
def _eval_mpmath(self):
|
359 |
+
return betainc_mpmath_fix, (*self.args, S(1))
|
360 |
+
|
361 |
+
def fdiff(self, argindex):
|
362 |
+
a, b, x1, x2 = self.args
|
363 |
+
if argindex == 3:
|
364 |
+
# Diff wrt x1
|
365 |
+
return -(1 - x1)**(b - 1)*x1**(a - 1) / beta(a, b)
|
366 |
+
elif argindex == 4:
|
367 |
+
# Diff wrt x2
|
368 |
+
return (1 - x2)**(b - 1)*x2**(a - 1) / beta(a, b)
|
369 |
+
else:
|
370 |
+
raise ArgumentIndexError(self, argindex)
|
371 |
+
|
372 |
+
def _eval_is_real(self):
|
373 |
+
if all(arg.is_real for arg in self.args):
|
374 |
+
return True
|
375 |
+
|
376 |
+
def _eval_conjugate(self):
|
377 |
+
return self.func(*map(conjugate, self.args))
|
378 |
+
|
379 |
+
def _eval_rewrite_as_Integral(self, a, b, x1, x2, **kwargs):
|
380 |
+
from sympy.integrals.integrals import Integral
|
381 |
+
t = Dummy('t')
|
382 |
+
integrand = t**(a - 1)*(1 - t)**(b - 1)
|
383 |
+
expr = Integral(integrand, (t, x1, x2))
|
384 |
+
return expr / Integral(integrand, (t, 0, 1))
|
385 |
+
|
386 |
+
def _eval_rewrite_as_hyper(self, a, b, x1, x2, **kwargs):
|
387 |
+
from sympy.functions.special.hyper import hyper
|
388 |
+
expr = (x2**a * hyper((a, 1 - b), (a + 1,), x2) - x1**a * hyper((a, 1 - b), (a + 1,), x1)) / a
|
389 |
+
return expr / beta(a, b)
|
venv/lib/python3.10/site-packages/sympy/functions/special/bsplines.py
ADDED
@@ -0,0 +1,351 @@
|
|
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|
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|
|
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|
|
|
|
|
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|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
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|
1 |
+
from sympy.core import S, sympify
|
2 |
+
from sympy.core.symbol import (Dummy, symbols)
|
3 |
+
from sympy.functions import Piecewise, piecewise_fold
|
4 |
+
from sympy.logic.boolalg import And
|
5 |
+
from sympy.sets.sets import Interval
|
6 |
+
|
7 |
+
from functools import lru_cache
|
8 |
+
|
9 |
+
|
10 |
+
def _ivl(cond, x):
|
11 |
+
"""return the interval corresponding to the condition
|
12 |
+
|
13 |
+
Conditions in spline's Piecewise give the range over
|
14 |
+
which an expression is valid like (lo <= x) & (x <= hi).
|
15 |
+
This function returns (lo, hi).
|
16 |
+
"""
|
17 |
+
if isinstance(cond, And) and len(cond.args) == 2:
|
18 |
+
a, b = cond.args
|
19 |
+
if a.lts == x:
|
20 |
+
a, b = b, a
|
21 |
+
return a.lts, b.gts
|
22 |
+
raise TypeError('unexpected cond type: %s' % cond)
|
23 |
+
|
24 |
+
|
25 |
+
def _add_splines(c, b1, d, b2, x):
|
26 |
+
"""Construct c*b1 + d*b2."""
|
27 |
+
|
28 |
+
if S.Zero in (b1, c):
|
29 |
+
rv = piecewise_fold(d * b2)
|
30 |
+
elif S.Zero in (b2, d):
|
31 |
+
rv = piecewise_fold(c * b1)
|
32 |
+
else:
|
33 |
+
new_args = []
|
34 |
+
# Just combining the Piecewise without any fancy optimization
|
35 |
+
p1 = piecewise_fold(c * b1)
|
36 |
+
p2 = piecewise_fold(d * b2)
|
37 |
+
|
38 |
+
# Search all Piecewise arguments except (0, True)
|
39 |
+
p2args = list(p2.args[:-1])
|
40 |
+
|
41 |
+
# This merging algorithm assumes the conditions in
|
42 |
+
# p1 and p2 are sorted
|
43 |
+
for arg in p1.args[:-1]:
|
44 |
+
expr = arg.expr
|
45 |
+
cond = arg.cond
|
46 |
+
|
47 |
+
lower = _ivl(cond, x)[0]
|
48 |
+
|
49 |
+
# Check p2 for matching conditions that can be merged
|
50 |
+
for i, arg2 in enumerate(p2args):
|
51 |
+
expr2 = arg2.expr
|
52 |
+
cond2 = arg2.cond
|
53 |
+
|
54 |
+
lower_2, upper_2 = _ivl(cond2, x)
|
55 |
+
if cond2 == cond:
|
56 |
+
# Conditions match, join expressions
|
57 |
+
expr += expr2
|
58 |
+
# Remove matching element
|
59 |
+
del p2args[i]
|
60 |
+
# No need to check the rest
|
61 |
+
break
|
62 |
+
elif lower_2 < lower and upper_2 <= lower:
|
63 |
+
# Check if arg2 condition smaller than arg1,
|
64 |
+
# add to new_args by itself (no match expected
|
65 |
+
# in p1)
|
66 |
+
new_args.append(arg2)
|
67 |
+
del p2args[i]
|
68 |
+
break
|
69 |
+
|
70 |
+
# Checked all, add expr and cond
|
71 |
+
new_args.append((expr, cond))
|
72 |
+
|
73 |
+
# Add remaining items from p2args
|
74 |
+
new_args.extend(p2args)
|
75 |
+
|
76 |
+
# Add final (0, True)
|
77 |
+
new_args.append((0, True))
|
78 |
+
|
79 |
+
rv = Piecewise(*new_args, evaluate=False)
|
80 |
+
|
81 |
+
return rv.expand()
|
82 |
+
|
83 |
+
|
84 |
+
@lru_cache(maxsize=128)
|
85 |
+
def bspline_basis(d, knots, n, x):
|
86 |
+
"""
|
87 |
+
The $n$-th B-spline at $x$ of degree $d$ with knots.
|
88 |
+
|
89 |
+
Explanation
|
90 |
+
===========
|
91 |
+
|
92 |
+
B-Splines are piecewise polynomials of degree $d$. They are defined on a
|
93 |
+
set of knots, which is a sequence of integers or floats.
|
94 |
+
|
95 |
+
Examples
|
96 |
+
========
|
97 |
+
|
98 |
+
The 0th degree splines have a value of 1 on a single interval:
|
99 |
+
|
100 |
+
>>> from sympy import bspline_basis
|
101 |
+
>>> from sympy.abc import x
|
102 |
+
>>> d = 0
|
103 |
+
>>> knots = tuple(range(5))
|
104 |
+
>>> bspline_basis(d, knots, 0, x)
|
105 |
+
Piecewise((1, (x >= 0) & (x <= 1)), (0, True))
|
106 |
+
|
107 |
+
For a given ``(d, knots)`` there are ``len(knots)-d-1`` B-splines
|
108 |
+
defined, that are indexed by ``n`` (starting at 0).
|
109 |
+
|
110 |
+
Here is an example of a cubic B-spline:
|
111 |
+
|
112 |
+
>>> bspline_basis(3, tuple(range(5)), 0, x)
|
113 |
+
Piecewise((x**3/6, (x >= 0) & (x <= 1)),
|
114 |
+
(-x**3/2 + 2*x**2 - 2*x + 2/3,
|
115 |
+
(x >= 1) & (x <= 2)),
|
116 |
+
(x**3/2 - 4*x**2 + 10*x - 22/3,
|
117 |
+
(x >= 2) & (x <= 3)),
|
118 |
+
(-x**3/6 + 2*x**2 - 8*x + 32/3,
|
119 |
+
(x >= 3) & (x <= 4)),
|
120 |
+
(0, True))
|
121 |
+
|
122 |
+
By repeating knot points, you can introduce discontinuities in the
|
123 |
+
B-splines and their derivatives:
|
124 |
+
|
125 |
+
>>> d = 1
|
126 |
+
>>> knots = (0, 0, 2, 3, 4)
|
127 |
+
>>> bspline_basis(d, knots, 0, x)
|
128 |
+
Piecewise((1 - x/2, (x >= 0) & (x <= 2)), (0, True))
|
129 |
+
|
130 |
+
It is quite time consuming to construct and evaluate B-splines. If
|
131 |
+
you need to evaluate a B-spline many times, it is best to lambdify them
|
132 |
+
first:
|
133 |
+
|
134 |
+
>>> from sympy import lambdify
|
135 |
+
>>> d = 3
|
136 |
+
>>> knots = tuple(range(10))
|
137 |
+
>>> b0 = bspline_basis(d, knots, 0, x)
|
138 |
+
>>> f = lambdify(x, b0)
|
139 |
+
>>> y = f(0.5)
|
140 |
+
|
141 |
+
Parameters
|
142 |
+
==========
|
143 |
+
|
144 |
+
d : integer
|
145 |
+
degree of bspline
|
146 |
+
|
147 |
+
knots : list of integer values
|
148 |
+
list of knots points of bspline
|
149 |
+
|
150 |
+
n : integer
|
151 |
+
$n$-th B-spline
|
152 |
+
|
153 |
+
x : symbol
|
154 |
+
|
155 |
+
See Also
|
156 |
+
========
|
157 |
+
|
158 |
+
bspline_basis_set
|
159 |
+
|
160 |
+
References
|
161 |
+
==========
|
162 |
+
|
163 |
+
.. [1] https://en.wikipedia.org/wiki/B-spline
|
164 |
+
|
165 |
+
"""
|
166 |
+
# make sure x has no assumptions so conditions don't evaluate
|
167 |
+
xvar = x
|
168 |
+
x = Dummy()
|
169 |
+
|
170 |
+
knots = tuple(sympify(k) for k in knots)
|
171 |
+
d = int(d)
|
172 |
+
n = int(n)
|
173 |
+
n_knots = len(knots)
|
174 |
+
n_intervals = n_knots - 1
|
175 |
+
if n + d + 1 > n_intervals:
|
176 |
+
raise ValueError("n + d + 1 must not exceed len(knots) - 1")
|
177 |
+
if d == 0:
|
178 |
+
result = Piecewise(
|
179 |
+
(S.One, Interval(knots[n], knots[n + 1]).contains(x)), (0, True)
|
180 |
+
)
|
181 |
+
elif d > 0:
|
182 |
+
denom = knots[n + d + 1] - knots[n + 1]
|
183 |
+
if denom != S.Zero:
|
184 |
+
B = (knots[n + d + 1] - x) / denom
|
185 |
+
b2 = bspline_basis(d - 1, knots, n + 1, x)
|
186 |
+
else:
|
187 |
+
b2 = B = S.Zero
|
188 |
+
|
189 |
+
denom = knots[n + d] - knots[n]
|
190 |
+
if denom != S.Zero:
|
191 |
+
A = (x - knots[n]) / denom
|
192 |
+
b1 = bspline_basis(d - 1, knots, n, x)
|
193 |
+
else:
|
194 |
+
b1 = A = S.Zero
|
195 |
+
|
196 |
+
result = _add_splines(A, b1, B, b2, x)
|
197 |
+
else:
|
198 |
+
raise ValueError("degree must be non-negative: %r" % n)
|
199 |
+
|
200 |
+
# return result with user-given x
|
201 |
+
return result.xreplace({x: xvar})
|
202 |
+
|
203 |
+
|
204 |
+
def bspline_basis_set(d, knots, x):
|
205 |
+
"""
|
206 |
+
Return the ``len(knots)-d-1`` B-splines at *x* of degree *d*
|
207 |
+
with *knots*.
|
208 |
+
|
209 |
+
Explanation
|
210 |
+
===========
|
211 |
+
|
212 |
+
This function returns a list of piecewise polynomials that are the
|
213 |
+
``len(knots)-d-1`` B-splines of degree *d* for the given knots.
|
214 |
+
This function calls ``bspline_basis(d, knots, n, x)`` for different
|
215 |
+
values of *n*.
|
216 |
+
|
217 |
+
Examples
|
218 |
+
========
|
219 |
+
|
220 |
+
>>> from sympy import bspline_basis_set
|
221 |
+
>>> from sympy.abc import x
|
222 |
+
>>> d = 2
|
223 |
+
>>> knots = range(5)
|
224 |
+
>>> splines = bspline_basis_set(d, knots, x)
|
225 |
+
>>> splines
|
226 |
+
[Piecewise((x**2/2, (x >= 0) & (x <= 1)),
|
227 |
+
(-x**2 + 3*x - 3/2, (x >= 1) & (x <= 2)),
|
228 |
+
(x**2/2 - 3*x + 9/2, (x >= 2) & (x <= 3)),
|
229 |
+
(0, True)),
|
230 |
+
Piecewise((x**2/2 - x + 1/2, (x >= 1) & (x <= 2)),
|
231 |
+
(-x**2 + 5*x - 11/2, (x >= 2) & (x <= 3)),
|
232 |
+
(x**2/2 - 4*x + 8, (x >= 3) & (x <= 4)),
|
233 |
+
(0, True))]
|
234 |
+
|
235 |
+
Parameters
|
236 |
+
==========
|
237 |
+
|
238 |
+
d : integer
|
239 |
+
degree of bspline
|
240 |
+
|
241 |
+
knots : list of integers
|
242 |
+
list of knots points of bspline
|
243 |
+
|
244 |
+
x : symbol
|
245 |
+
|
246 |
+
See Also
|
247 |
+
========
|
248 |
+
|
249 |
+
bspline_basis
|
250 |
+
|
251 |
+
"""
|
252 |
+
n_splines = len(knots) - d - 1
|
253 |
+
return [bspline_basis(d, tuple(knots), i, x) for i in range(n_splines)]
|
254 |
+
|
255 |
+
|
256 |
+
def interpolating_spline(d, x, X, Y):
|
257 |
+
"""
|
258 |
+
Return spline of degree *d*, passing through the given *X*
|
259 |
+
and *Y* values.
|
260 |
+
|
261 |
+
Explanation
|
262 |
+
===========
|
263 |
+
|
264 |
+
This function returns a piecewise function such that each part is
|
265 |
+
a polynomial of degree not greater than *d*. The value of *d*
|
266 |
+
must be 1 or greater and the values of *X* must be strictly
|
267 |
+
increasing.
|
268 |
+
|
269 |
+
Examples
|
270 |
+
========
|
271 |
+
|
272 |
+
>>> from sympy import interpolating_spline
|
273 |
+
>>> from sympy.abc import x
|
274 |
+
>>> interpolating_spline(1, x, [1, 2, 4, 7], [3, 6, 5, 7])
|
275 |
+
Piecewise((3*x, (x >= 1) & (x <= 2)),
|
276 |
+
(7 - x/2, (x >= 2) & (x <= 4)),
|
277 |
+
(2*x/3 + 7/3, (x >= 4) & (x <= 7)))
|
278 |
+
>>> interpolating_spline(3, x, [-2, 0, 1, 3, 4], [4, 2, 1, 1, 3])
|
279 |
+
Piecewise((7*x**3/117 + 7*x**2/117 - 131*x/117 + 2, (x >= -2) & (x <= 1)),
|
280 |
+
(10*x**3/117 - 2*x**2/117 - 122*x/117 + 77/39, (x >= 1) & (x <= 4)))
|
281 |
+
|
282 |
+
Parameters
|
283 |
+
==========
|
284 |
+
|
285 |
+
d : integer
|
286 |
+
Degree of Bspline strictly greater than equal to one
|
287 |
+
|
288 |
+
x : symbol
|
289 |
+
|
290 |
+
X : list of strictly increasing real values
|
291 |
+
list of X coordinates through which the spline passes
|
292 |
+
|
293 |
+
Y : list of real values
|
294 |
+
list of corresponding Y coordinates through which the spline passes
|
295 |
+
|
296 |
+
See Also
|
297 |
+
========
|
298 |
+
|
299 |
+
bspline_basis_set, interpolating_poly
|
300 |
+
|
301 |
+
"""
|
302 |
+
from sympy.solvers.solveset import linsolve
|
303 |
+
from sympy.matrices.dense import Matrix
|
304 |
+
|
305 |
+
# Input sanitization
|
306 |
+
d = sympify(d)
|
307 |
+
if not (d.is_Integer and d.is_positive):
|
308 |
+
raise ValueError("Spline degree must be a positive integer, not %s." % d)
|
309 |
+
if len(X) != len(Y):
|
310 |
+
raise ValueError("Number of X and Y coordinates must be the same.")
|
311 |
+
if len(X) < d + 1:
|
312 |
+
raise ValueError("Degree must be less than the number of control points.")
|
313 |
+
if not all(a < b for a, b in zip(X, X[1:])):
|
314 |
+
raise ValueError("The x-coordinates must be strictly increasing.")
|
315 |
+
X = [sympify(i) for i in X]
|
316 |
+
|
317 |
+
# Evaluating knots value
|
318 |
+
if d.is_odd:
|
319 |
+
j = (d + 1) // 2
|
320 |
+
interior_knots = X[j:-j]
|
321 |
+
else:
|
322 |
+
j = d // 2
|
323 |
+
interior_knots = [
|
324 |
+
(a + b)/2 for a, b in zip(X[j : -j - 1], X[j + 1 : -j])
|
325 |
+
]
|
326 |
+
|
327 |
+
knots = [X[0]] * (d + 1) + list(interior_knots) + [X[-1]] * (d + 1)
|
328 |
+
|
329 |
+
basis = bspline_basis_set(d, knots, x)
|
330 |
+
|
331 |
+
A = [[b.subs(x, v) for b in basis] for v in X]
|
332 |
+
|
333 |
+
coeff = linsolve((Matrix(A), Matrix(Y)), symbols("c0:{}".format(len(X)), cls=Dummy))
|
334 |
+
coeff = list(coeff)[0]
|
335 |
+
intervals = {c for b in basis for (e, c) in b.args if c != True}
|
336 |
+
|
337 |
+
# Sorting the intervals
|
338 |
+
# ival contains the end-points of each interval
|
339 |
+
ival = [_ivl(c, x) for c in intervals]
|
340 |
+
com = zip(ival, intervals)
|
341 |
+
com = sorted(com, key=lambda x: x[0])
|
342 |
+
intervals = [y for x, y in com]
|
343 |
+
|
344 |
+
basis_dicts = [{c: e for (e, c) in b.args} for b in basis]
|
345 |
+
spline = []
|
346 |
+
for i in intervals:
|
347 |
+
piece = sum(
|
348 |
+
[c * d.get(i, S.Zero) for (c, d) in zip(coeff, basis_dicts)], S.Zero
|
349 |
+
)
|
350 |
+
spline.append((piece, i))
|
351 |
+
return Piecewise(*spline)
|
venv/lib/python3.10/site-packages/sympy/functions/special/delta_functions.py
ADDED
@@ -0,0 +1,664 @@
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|
|
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|
|
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|
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|
|
|
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|
|
|
|
|
|
|
|
|
|
|
|
1 |
+
from sympy.core import S, diff
|
2 |
+
from sympy.core.function import Function, ArgumentIndexError
|
3 |
+
from sympy.core.logic import fuzzy_not
|
4 |
+
from sympy.core.relational import Eq, Ne
|
5 |
+
from sympy.functions.elementary.complexes import im, sign
|
6 |
+
from sympy.functions.elementary.piecewise import Piecewise
|
7 |
+
from sympy.polys.polyerrors import PolynomialError
|
8 |
+
from sympy.polys.polyroots import roots
|
9 |
+
from sympy.utilities.misc import filldedent
|
10 |
+
|
11 |
+
|
12 |
+
###############################################################################
|
13 |
+
################################ DELTA FUNCTION ###############################
|
14 |
+
###############################################################################
|
15 |
+
|
16 |
+
|
17 |
+
class DiracDelta(Function):
|
18 |
+
r"""
|
19 |
+
The DiracDelta function and its derivatives.
|
20 |
+
|
21 |
+
Explanation
|
22 |
+
===========
|
23 |
+
|
24 |
+
DiracDelta is not an ordinary function. It can be rigorously defined either
|
25 |
+
as a distribution or as a measure.
|
26 |
+
|
27 |
+
DiracDelta only makes sense in definite integrals, and in particular,
|
28 |
+
integrals of the form ``Integral(f(x)*DiracDelta(x - x0), (x, a, b))``,
|
29 |
+
where it equals ``f(x0)`` if ``a <= x0 <= b`` and ``0`` otherwise. Formally,
|
30 |
+
DiracDelta acts in some ways like a function that is ``0`` everywhere except
|
31 |
+
at ``0``, but in many ways it also does not. It can often be useful to treat
|
32 |
+
DiracDelta in formal ways, building up and manipulating expressions with
|
33 |
+
delta functions (which may eventually be integrated), but care must be taken
|
34 |
+
to not treat it as a real function. SymPy's ``oo`` is similar. It only
|
35 |
+
truly makes sense formally in certain contexts (such as integration limits),
|
36 |
+
but SymPy allows its use everywhere, and it tries to be consistent with
|
37 |
+
operations on it (like ``1/oo``), but it is easy to get into trouble and get
|
38 |
+
wrong results if ``oo`` is treated too much like a number. Similarly, if
|
39 |
+
DiracDelta is treated too much like a function, it is easy to get wrong or
|
40 |
+
nonsensical results.
|
41 |
+
|
42 |
+
DiracDelta function has the following properties:
|
43 |
+
|
44 |
+
1) $\frac{d}{d x} \theta(x) = \delta(x)$
|
45 |
+
2) $\int_{-\infty}^\infty \delta(x - a)f(x)\, dx = f(a)$ and $\int_{a-
|
46 |
+
\epsilon}^{a+\epsilon} \delta(x - a)f(x)\, dx = f(a)$
|
47 |
+
3) $\delta(x) = 0$ for all $x \neq 0$
|
48 |
+
4) $\delta(g(x)) = \sum_i \frac{\delta(x - x_i)}{\|g'(x_i)\|}$ where $x_i$
|
49 |
+
are the roots of $g$
|
50 |
+
5) $\delta(-x) = \delta(x)$
|
51 |
+
|
52 |
+
Derivatives of ``k``-th order of DiracDelta have the following properties:
|
53 |
+
|
54 |
+
6) $\delta(x, k) = 0$ for all $x \neq 0$
|
55 |
+
7) $\delta(-x, k) = -\delta(x, k)$ for odd $k$
|
56 |
+
8) $\delta(-x, k) = \delta(x, k)$ for even $k$
|
57 |
+
|
58 |
+
Examples
|
59 |
+
========
|
60 |
+
|
61 |
+
>>> from sympy import DiracDelta, diff, pi
|
62 |
+
>>> from sympy.abc import x, y
|
63 |
+
|
64 |
+
>>> DiracDelta(x)
|
65 |
+
DiracDelta(x)
|
66 |
+
>>> DiracDelta(1)
|
67 |
+
0
|
68 |
+
>>> DiracDelta(-1)
|
69 |
+
0
|
70 |
+
>>> DiracDelta(pi)
|
71 |
+
0
|
72 |
+
>>> DiracDelta(x - 4).subs(x, 4)
|
73 |
+
DiracDelta(0)
|
74 |
+
>>> diff(DiracDelta(x))
|
75 |
+
DiracDelta(x, 1)
|
76 |
+
>>> diff(DiracDelta(x - 1), x, 2)
|
77 |
+
DiracDelta(x - 1, 2)
|
78 |
+
>>> diff(DiracDelta(x**2 - 1), x, 2)
|
79 |
+
2*(2*x**2*DiracDelta(x**2 - 1, 2) + DiracDelta(x**2 - 1, 1))
|
80 |
+
>>> DiracDelta(3*x).is_simple(x)
|
81 |
+
True
|
82 |
+
>>> DiracDelta(x**2).is_simple(x)
|
83 |
+
False
|
84 |
+
>>> DiracDelta((x**2 - 1)*y).expand(diracdelta=True, wrt=x)
|
85 |
+
DiracDelta(x - 1)/(2*Abs(y)) + DiracDelta(x + 1)/(2*Abs(y))
|
86 |
+
|
87 |
+
See Also
|
88 |
+
========
|
89 |
+
|
90 |
+
Heaviside
|
91 |
+
sympy.simplify.simplify.simplify, is_simple
|
92 |
+
sympy.functions.special.tensor_functions.KroneckerDelta
|
93 |
+
|
94 |
+
References
|
95 |
+
==========
|
96 |
+
|
97 |
+
.. [1] https://mathworld.wolfram.com/DeltaFunction.html
|
98 |
+
|
99 |
+
"""
|
100 |
+
|
101 |
+
is_real = True
|
102 |
+
|
103 |
+
def fdiff(self, argindex=1):
|
104 |
+
"""
|
105 |
+
Returns the first derivative of a DiracDelta Function.
|
106 |
+
|
107 |
+
Explanation
|
108 |
+
===========
|
109 |
+
|
110 |
+
The difference between ``diff()`` and ``fdiff()`` is: ``diff()`` is the
|
111 |
+
user-level function and ``fdiff()`` is an object method. ``fdiff()`` is
|
112 |
+
a convenience method available in the ``Function`` class. It returns
|
113 |
+
the derivative of the function without considering the chain rule.
|
114 |
+
``diff(function, x)`` calls ``Function._eval_derivative`` which in turn
|
115 |
+
calls ``fdiff()`` internally to compute the derivative of the function.
|
116 |
+
|
117 |
+
Examples
|
118 |
+
========
|
119 |
+
|
120 |
+
>>> from sympy import DiracDelta, diff
|
121 |
+
>>> from sympy.abc import x
|
122 |
+
|
123 |
+
>>> DiracDelta(x).fdiff()
|
124 |
+
DiracDelta(x, 1)
|
125 |
+
|
126 |
+
>>> DiracDelta(x, 1).fdiff()
|
127 |
+
DiracDelta(x, 2)
|
128 |
+
|
129 |
+
>>> DiracDelta(x**2 - 1).fdiff()
|
130 |
+
DiracDelta(x**2 - 1, 1)
|
131 |
+
|
132 |
+
>>> diff(DiracDelta(x, 1)).fdiff()
|
133 |
+
DiracDelta(x, 3)
|
134 |
+
|
135 |
+
Parameters
|
136 |
+
==========
|
137 |
+
|
138 |
+
argindex : integer
|
139 |
+
degree of derivative
|
140 |
+
|
141 |
+
"""
|
142 |
+
if argindex == 1:
|
143 |
+
#I didn't know if there is a better way to handle default arguments
|
144 |
+
k = 0
|
145 |
+
if len(self.args) > 1:
|
146 |
+
k = self.args[1]
|
147 |
+
return self.func(self.args[0], k + 1)
|
148 |
+
else:
|
149 |
+
raise ArgumentIndexError(self, argindex)
|
150 |
+
|
151 |
+
@classmethod
|
152 |
+
def eval(cls, arg, k=S.Zero):
|
153 |
+
"""
|
154 |
+
Returns a simplified form or a value of DiracDelta depending on the
|
155 |
+
argument passed by the DiracDelta object.
|
156 |
+
|
157 |
+
Explanation
|
158 |
+
===========
|
159 |
+
|
160 |
+
The ``eval()`` method is automatically called when the ``DiracDelta``
|
161 |
+
class is about to be instantiated and it returns either some simplified
|
162 |
+
instance or the unevaluated instance depending on the argument passed.
|
163 |
+
In other words, ``eval()`` method is not needed to be called explicitly,
|
164 |
+
it is being called and evaluated once the object is called.
|
165 |
+
|
166 |
+
Examples
|
167 |
+
========
|
168 |
+
|
169 |
+
>>> from sympy import DiracDelta, S
|
170 |
+
>>> from sympy.abc import x
|
171 |
+
|
172 |
+
>>> DiracDelta(x)
|
173 |
+
DiracDelta(x)
|
174 |
+
|
175 |
+
>>> DiracDelta(-x, 1)
|
176 |
+
-DiracDelta(x, 1)
|
177 |
+
|
178 |
+
>>> DiracDelta(1)
|
179 |
+
0
|
180 |
+
|
181 |
+
>>> DiracDelta(5, 1)
|
182 |
+
0
|
183 |
+
|
184 |
+
>>> DiracDelta(0)
|
185 |
+
DiracDelta(0)
|
186 |
+
|
187 |
+
>>> DiracDelta(-1)
|
188 |
+
0
|
189 |
+
|
190 |
+
>>> DiracDelta(S.NaN)
|
191 |
+
nan
|
192 |
+
|
193 |
+
>>> DiracDelta(x - 100).subs(x, 5)
|
194 |
+
0
|
195 |
+
|
196 |
+
>>> DiracDelta(x - 100).subs(x, 100)
|
197 |
+
DiracDelta(0)
|
198 |
+
|
199 |
+
Parameters
|
200 |
+
==========
|
201 |
+
|
202 |
+
k : integer
|
203 |
+
order of derivative
|
204 |
+
|
205 |
+
arg : argument passed to DiracDelta
|
206 |
+
|
207 |
+
"""
|
208 |
+
if not k.is_Integer or k.is_negative:
|
209 |
+
raise ValueError("Error: the second argument of DiracDelta must be \
|
210 |
+
a non-negative integer, %s given instead." % (k,))
|
211 |
+
if arg is S.NaN:
|
212 |
+
return S.NaN
|
213 |
+
if arg.is_nonzero:
|
214 |
+
return S.Zero
|
215 |
+
if fuzzy_not(im(arg).is_zero):
|
216 |
+
raise ValueError(filldedent('''
|
217 |
+
Function defined only for Real Values.
|
218 |
+
Complex part: %s found in %s .''' % (
|
219 |
+
repr(im(arg)), repr(arg))))
|
220 |
+
c, nc = arg.args_cnc()
|
221 |
+
if c and c[0] is S.NegativeOne:
|
222 |
+
# keep this fast and simple instead of using
|
223 |
+
# could_extract_minus_sign
|
224 |
+
if k.is_odd:
|
225 |
+
return -cls(-arg, k)
|
226 |
+
elif k.is_even:
|
227 |
+
return cls(-arg, k) if k else cls(-arg)
|
228 |
+
elif k.is_zero:
|
229 |
+
return cls(arg, evaluate=False)
|
230 |
+
|
231 |
+
def _eval_expand_diracdelta(self, **hints):
|
232 |
+
"""
|
233 |
+
Compute a simplified representation of the function using
|
234 |
+
property number 4. Pass ``wrt`` as a hint to expand the expression
|
235 |
+
with respect to a particular variable.
|
236 |
+
|
237 |
+
Explanation
|
238 |
+
===========
|
239 |
+
|
240 |
+
``wrt`` is:
|
241 |
+
|
242 |
+
- a variable with respect to which a DiracDelta expression will
|
243 |
+
get expanded.
|
244 |
+
|
245 |
+
Examples
|
246 |
+
========
|
247 |
+
|
248 |
+
>>> from sympy import DiracDelta
|
249 |
+
>>> from sympy.abc import x, y
|
250 |
+
|
251 |
+
>>> DiracDelta(x*y).expand(diracdelta=True, wrt=x)
|
252 |
+
DiracDelta(x)/Abs(y)
|
253 |
+
>>> DiracDelta(x*y).expand(diracdelta=True, wrt=y)
|
254 |
+
DiracDelta(y)/Abs(x)
|
255 |
+
|
256 |
+
>>> DiracDelta(x**2 + x - 2).expand(diracdelta=True, wrt=x)
|
257 |
+
DiracDelta(x - 1)/3 + DiracDelta(x + 2)/3
|
258 |
+
|
259 |
+
See Also
|
260 |
+
========
|
261 |
+
|
262 |
+
is_simple, Diracdelta
|
263 |
+
|
264 |
+
"""
|
265 |
+
wrt = hints.get('wrt', None)
|
266 |
+
if wrt is None:
|
267 |
+
free = self.free_symbols
|
268 |
+
if len(free) == 1:
|
269 |
+
wrt = free.pop()
|
270 |
+
else:
|
271 |
+
raise TypeError(filldedent('''
|
272 |
+
When there is more than 1 free symbol or variable in the expression,
|
273 |
+
the 'wrt' keyword is required as a hint to expand when using the
|
274 |
+
DiracDelta hint.'''))
|
275 |
+
|
276 |
+
if not self.args[0].has(wrt) or (len(self.args) > 1 and self.args[1] != 0 ):
|
277 |
+
return self
|
278 |
+
try:
|
279 |
+
argroots = roots(self.args[0], wrt)
|
280 |
+
result = 0
|
281 |
+
valid = True
|
282 |
+
darg = abs(diff(self.args[0], wrt))
|
283 |
+
for r, m in argroots.items():
|
284 |
+
if r.is_real is not False and m == 1:
|
285 |
+
result += self.func(wrt - r)/darg.subs(wrt, r)
|
286 |
+
else:
|
287 |
+
# don't handle non-real and if m != 1 then
|
288 |
+
# a polynomial will have a zero in the derivative (darg)
|
289 |
+
# at r
|
290 |
+
valid = False
|
291 |
+
break
|
292 |
+
if valid:
|
293 |
+
return result
|
294 |
+
except PolynomialError:
|
295 |
+
pass
|
296 |
+
return self
|
297 |
+
|
298 |
+
def is_simple(self, x):
|
299 |
+
"""
|
300 |
+
Tells whether the argument(args[0]) of DiracDelta is a linear
|
301 |
+
expression in *x*.
|
302 |
+
|
303 |
+
Examples
|
304 |
+
========
|
305 |
+
|
306 |
+
>>> from sympy import DiracDelta, cos
|
307 |
+
>>> from sympy.abc import x, y
|
308 |
+
|
309 |
+
>>> DiracDelta(x*y).is_simple(x)
|
310 |
+
True
|
311 |
+
>>> DiracDelta(x*y).is_simple(y)
|
312 |
+
True
|
313 |
+
|
314 |
+
>>> DiracDelta(x**2 + x - 2).is_simple(x)
|
315 |
+
False
|
316 |
+
|
317 |
+
>>> DiracDelta(cos(x)).is_simple(x)
|
318 |
+
False
|
319 |
+
|
320 |
+
Parameters
|
321 |
+
==========
|
322 |
+
|
323 |
+
x : can be a symbol
|
324 |
+
|
325 |
+
See Also
|
326 |
+
========
|
327 |
+
|
328 |
+
sympy.simplify.simplify.simplify, DiracDelta
|
329 |
+
|
330 |
+
"""
|
331 |
+
p = self.args[0].as_poly(x)
|
332 |
+
if p:
|
333 |
+
return p.degree() == 1
|
334 |
+
return False
|
335 |
+
|
336 |
+
def _eval_rewrite_as_Piecewise(self, *args, **kwargs):
|
337 |
+
"""
|
338 |
+
Represents DiracDelta in a piecewise form.
|
339 |
+
|
340 |
+
Examples
|
341 |
+
========
|
342 |
+
|
343 |
+
>>> from sympy import DiracDelta, Piecewise, Symbol
|
344 |
+
>>> x = Symbol('x')
|
345 |
+
|
346 |
+
>>> DiracDelta(x).rewrite(Piecewise)
|
347 |
+
Piecewise((DiracDelta(0), Eq(x, 0)), (0, True))
|
348 |
+
|
349 |
+
>>> DiracDelta(x - 5).rewrite(Piecewise)
|
350 |
+
Piecewise((DiracDelta(0), Eq(x, 5)), (0, True))
|
351 |
+
|
352 |
+
>>> DiracDelta(x**2 - 5).rewrite(Piecewise)
|
353 |
+
Piecewise((DiracDelta(0), Eq(x**2, 5)), (0, True))
|
354 |
+
|
355 |
+
>>> DiracDelta(x - 5, 4).rewrite(Piecewise)
|
356 |
+
DiracDelta(x - 5, 4)
|
357 |
+
|
358 |
+
"""
|
359 |
+
if len(args) == 1:
|
360 |
+
return Piecewise((DiracDelta(0), Eq(args[0], 0)), (0, True))
|
361 |
+
|
362 |
+
def _eval_rewrite_as_SingularityFunction(self, *args, **kwargs):
|
363 |
+
"""
|
364 |
+
Returns the DiracDelta expression written in the form of Singularity
|
365 |
+
Functions.
|
366 |
+
|
367 |
+
"""
|
368 |
+
from sympy.solvers import solve
|
369 |
+
from sympy.functions.special.singularity_functions import SingularityFunction
|
370 |
+
if self == DiracDelta(0):
|
371 |
+
return SingularityFunction(0, 0, -1)
|
372 |
+
if self == DiracDelta(0, 1):
|
373 |
+
return SingularityFunction(0, 0, -2)
|
374 |
+
free = self.free_symbols
|
375 |
+
if len(free) == 1:
|
376 |
+
x = (free.pop())
|
377 |
+
if len(args) == 1:
|
378 |
+
return SingularityFunction(x, solve(args[0], x)[0], -1)
|
379 |
+
return SingularityFunction(x, solve(args[0], x)[0], -args[1] - 1)
|
380 |
+
else:
|
381 |
+
# I don't know how to handle the case for DiracDelta expressions
|
382 |
+
# having arguments with more than one variable.
|
383 |
+
raise TypeError(filldedent('''
|
384 |
+
rewrite(SingularityFunction) does not support
|
385 |
+
arguments with more that one variable.'''))
|
386 |
+
|
387 |
+
|
388 |
+
###############################################################################
|
389 |
+
############################## HEAVISIDE FUNCTION #############################
|
390 |
+
###############################################################################
|
391 |
+
|
392 |
+
|
393 |
+
class Heaviside(Function):
|
394 |
+
r"""
|
395 |
+
Heaviside step function.
|
396 |
+
|
397 |
+
Explanation
|
398 |
+
===========
|
399 |
+
|
400 |
+
The Heaviside step function has the following properties:
|
401 |
+
|
402 |
+
1) $\frac{d}{d x} \theta(x) = \delta(x)$
|
403 |
+
2) $\theta(x) = \begin{cases} 0 & \text{for}\: x < 0 \\ \frac{1}{2} &
|
404 |
+
\text{for}\: x = 0 \\1 & \text{for}\: x > 0 \end{cases}$
|
405 |
+
3) $\frac{d}{d x} \max(x, 0) = \theta(x)$
|
406 |
+
|
407 |
+
Heaviside(x) is printed as $\theta(x)$ with the SymPy LaTeX printer.
|
408 |
+
|
409 |
+
The value at 0 is set differently in different fields. SymPy uses 1/2,
|
410 |
+
which is a convention from electronics and signal processing, and is
|
411 |
+
consistent with solving improper integrals by Fourier transform and
|
412 |
+
convolution.
|
413 |
+
|
414 |
+
To specify a different value of Heaviside at ``x=0``, a second argument
|
415 |
+
can be given. Using ``Heaviside(x, nan)`` gives an expression that will
|
416 |
+
evaluate to nan for x=0.
|
417 |
+
|
418 |
+
.. versionchanged:: 1.9 ``Heaviside(0)`` now returns 1/2 (before: undefined)
|
419 |
+
|
420 |
+
Examples
|
421 |
+
========
|
422 |
+
|
423 |
+
>>> from sympy import Heaviside, nan
|
424 |
+
>>> from sympy.abc import x
|
425 |
+
>>> Heaviside(9)
|
426 |
+
1
|
427 |
+
>>> Heaviside(-9)
|
428 |
+
0
|
429 |
+
>>> Heaviside(0)
|
430 |
+
1/2
|
431 |
+
>>> Heaviside(0, nan)
|
432 |
+
nan
|
433 |
+
>>> (Heaviside(x) + 1).replace(Heaviside(x), Heaviside(x, 1))
|
434 |
+
Heaviside(x, 1) + 1
|
435 |
+
|
436 |
+
See Also
|
437 |
+
========
|
438 |
+
|
439 |
+
DiracDelta
|
440 |
+
|
441 |
+
References
|
442 |
+
==========
|
443 |
+
|
444 |
+
.. [1] https://mathworld.wolfram.com/HeavisideStepFunction.html
|
445 |
+
.. [2] https://dlmf.nist.gov/1.16#iv
|
446 |
+
|
447 |
+
"""
|
448 |
+
|
449 |
+
is_real = True
|
450 |
+
|
451 |
+
def fdiff(self, argindex=1):
|
452 |
+
"""
|
453 |
+
Returns the first derivative of a Heaviside Function.
|
454 |
+
|
455 |
+
Examples
|
456 |
+
========
|
457 |
+
|
458 |
+
>>> from sympy import Heaviside, diff
|
459 |
+
>>> from sympy.abc import x
|
460 |
+
|
461 |
+
>>> Heaviside(x).fdiff()
|
462 |
+
DiracDelta(x)
|
463 |
+
|
464 |
+
>>> Heaviside(x**2 - 1).fdiff()
|
465 |
+
DiracDelta(x**2 - 1)
|
466 |
+
|
467 |
+
>>> diff(Heaviside(x)).fdiff()
|
468 |
+
DiracDelta(x, 1)
|
469 |
+
|
470 |
+
Parameters
|
471 |
+
==========
|
472 |
+
|
473 |
+
argindex : integer
|
474 |
+
order of derivative
|
475 |
+
|
476 |
+
"""
|
477 |
+
if argindex == 1:
|
478 |
+
return DiracDelta(self.args[0])
|
479 |
+
else:
|
480 |
+
raise ArgumentIndexError(self, argindex)
|
481 |
+
|
482 |
+
def __new__(cls, arg, H0=S.Half, **options):
|
483 |
+
if isinstance(H0, Heaviside) and len(H0.args) == 1:
|
484 |
+
H0 = S.Half
|
485 |
+
return super(cls, cls).__new__(cls, arg, H0, **options)
|
486 |
+
|
487 |
+
@property
|
488 |
+
def pargs(self):
|
489 |
+
"""Args without default S.Half"""
|
490 |
+
args = self.args
|
491 |
+
if args[1] is S.Half:
|
492 |
+
args = args[:1]
|
493 |
+
return args
|
494 |
+
|
495 |
+
@classmethod
|
496 |
+
def eval(cls, arg, H0=S.Half):
|
497 |
+
"""
|
498 |
+
Returns a simplified form or a value of Heaviside depending on the
|
499 |
+
argument passed by the Heaviside object.
|
500 |
+
|
501 |
+
Explanation
|
502 |
+
===========
|
503 |
+
|
504 |
+
The ``eval()`` method is automatically called when the ``Heaviside``
|
505 |
+
class is about to be instantiated and it returns either some simplified
|
506 |
+
instance or the unevaluated instance depending on the argument passed.
|
507 |
+
In other words, ``eval()`` method is not needed to be called explicitly,
|
508 |
+
it is being called and evaluated once the object is called.
|
509 |
+
|
510 |
+
Examples
|
511 |
+
========
|
512 |
+
|
513 |
+
>>> from sympy import Heaviside, S
|
514 |
+
>>> from sympy.abc import x
|
515 |
+
|
516 |
+
>>> Heaviside(x)
|
517 |
+
Heaviside(x)
|
518 |
+
|
519 |
+
>>> Heaviside(19)
|
520 |
+
1
|
521 |
+
|
522 |
+
>>> Heaviside(0)
|
523 |
+
1/2
|
524 |
+
|
525 |
+
>>> Heaviside(0, 1)
|
526 |
+
1
|
527 |
+
|
528 |
+
>>> Heaviside(-5)
|
529 |
+
0
|
530 |
+
|
531 |
+
>>> Heaviside(S.NaN)
|
532 |
+
nan
|
533 |
+
|
534 |
+
>>> Heaviside(x - 100).subs(x, 5)
|
535 |
+
0
|
536 |
+
|
537 |
+
>>> Heaviside(x - 100).subs(x, 105)
|
538 |
+
1
|
539 |
+
|
540 |
+
Parameters
|
541 |
+
==========
|
542 |
+
|
543 |
+
arg : argument passed by Heaviside object
|
544 |
+
|
545 |
+
H0 : value of Heaviside(0)
|
546 |
+
|
547 |
+
"""
|
548 |
+
if arg.is_extended_negative:
|
549 |
+
return S.Zero
|
550 |
+
elif arg.is_extended_positive:
|
551 |
+
return S.One
|
552 |
+
elif arg.is_zero:
|
553 |
+
return H0
|
554 |
+
elif arg is S.NaN:
|
555 |
+
return S.NaN
|
556 |
+
elif fuzzy_not(im(arg).is_zero):
|
557 |
+
raise ValueError("Function defined only for Real Values. Complex part: %s found in %s ." % (repr(im(arg)), repr(arg)) )
|
558 |
+
|
559 |
+
def _eval_rewrite_as_Piecewise(self, arg, H0=None, **kwargs):
|
560 |
+
"""
|
561 |
+
Represents Heaviside in a Piecewise form.
|
562 |
+
|
563 |
+
Examples
|
564 |
+
========
|
565 |
+
|
566 |
+
>>> from sympy import Heaviside, Piecewise, Symbol, nan
|
567 |
+
>>> x = Symbol('x')
|
568 |
+
|
569 |
+
>>> Heaviside(x).rewrite(Piecewise)
|
570 |
+
Piecewise((0, x < 0), (1/2, Eq(x, 0)), (1, True))
|
571 |
+
|
572 |
+
>>> Heaviside(x,nan).rewrite(Piecewise)
|
573 |
+
Piecewise((0, x < 0), (nan, Eq(x, 0)), (1, True))
|
574 |
+
|
575 |
+
>>> Heaviside(x - 5).rewrite(Piecewise)
|
576 |
+
Piecewise((0, x < 5), (1/2, Eq(x, 5)), (1, True))
|
577 |
+
|
578 |
+
>>> Heaviside(x**2 - 1).rewrite(Piecewise)
|
579 |
+
Piecewise((0, x**2 < 1), (1/2, Eq(x**2, 1)), (1, True))
|
580 |
+
|
581 |
+
"""
|
582 |
+
if H0 == 0:
|
583 |
+
return Piecewise((0, arg <= 0), (1, True))
|
584 |
+
if H0 == 1:
|
585 |
+
return Piecewise((0, arg < 0), (1, True))
|
586 |
+
return Piecewise((0, arg < 0), (H0, Eq(arg, 0)), (1, True))
|
587 |
+
|
588 |
+
def _eval_rewrite_as_sign(self, arg, H0=S.Half, **kwargs):
|
589 |
+
"""
|
590 |
+
Represents the Heaviside function in the form of sign function.
|
591 |
+
|
592 |
+
Explanation
|
593 |
+
===========
|
594 |
+
|
595 |
+
The value of Heaviside(0) must be 1/2 for rewriting as sign to be
|
596 |
+
strictly equivalent. For easier usage, we also allow this rewriting
|
597 |
+
when Heaviside(0) is undefined.
|
598 |
+
|
599 |
+
Examples
|
600 |
+
========
|
601 |
+
|
602 |
+
>>> from sympy import Heaviside, Symbol, sign, nan
|
603 |
+
>>> x = Symbol('x', real=True)
|
604 |
+
>>> y = Symbol('y')
|
605 |
+
|
606 |
+
>>> Heaviside(x).rewrite(sign)
|
607 |
+
sign(x)/2 + 1/2
|
608 |
+
|
609 |
+
>>> Heaviside(x, 0).rewrite(sign)
|
610 |
+
Piecewise((sign(x)/2 + 1/2, Ne(x, 0)), (0, True))
|
611 |
+
|
612 |
+
>>> Heaviside(x, nan).rewrite(sign)
|
613 |
+
Piecewise((sign(x)/2 + 1/2, Ne(x, 0)), (nan, True))
|
614 |
+
|
615 |
+
>>> Heaviside(x - 2).rewrite(sign)
|
616 |
+
sign(x - 2)/2 + 1/2
|
617 |
+
|
618 |
+
>>> Heaviside(x**2 - 2*x + 1).rewrite(sign)
|
619 |
+
sign(x**2 - 2*x + 1)/2 + 1/2
|
620 |
+
|
621 |
+
>>> Heaviside(y).rewrite(sign)
|
622 |
+
Heaviside(y)
|
623 |
+
|
624 |
+
>>> Heaviside(y**2 - 2*y + 1).rewrite(sign)
|
625 |
+
Heaviside(y**2 - 2*y + 1)
|
626 |
+
|
627 |
+
See Also
|
628 |
+
========
|
629 |
+
|
630 |
+
sign
|
631 |
+
|
632 |
+
"""
|
633 |
+
if arg.is_extended_real:
|
634 |
+
pw1 = Piecewise(
|
635 |
+
((sign(arg) + 1)/2, Ne(arg, 0)),
|
636 |
+
(Heaviside(0, H0=H0), True))
|
637 |
+
pw2 = Piecewise(
|
638 |
+
((sign(arg) + 1)/2, Eq(Heaviside(0, H0=H0), S.Half)),
|
639 |
+
(pw1, True))
|
640 |
+
return pw2
|
641 |
+
|
642 |
+
def _eval_rewrite_as_SingularityFunction(self, args, H0=S.Half, **kwargs):
|
643 |
+
"""
|
644 |
+
Returns the Heaviside expression written in the form of Singularity
|
645 |
+
Functions.
|
646 |
+
|
647 |
+
"""
|
648 |
+
from sympy.solvers import solve
|
649 |
+
from sympy.functions.special.singularity_functions import SingularityFunction
|
650 |
+
if self == Heaviside(0):
|
651 |
+
return SingularityFunction(0, 0, 0)
|
652 |
+
free = self.free_symbols
|
653 |
+
if len(free) == 1:
|
654 |
+
x = (free.pop())
|
655 |
+
return SingularityFunction(x, solve(args, x)[0], 0)
|
656 |
+
# TODO
|
657 |
+
# ((x - 5)**3*Heaviside(x - 5)).rewrite(SingularityFunction) should output
|
658 |
+
# SingularityFunction(x, 5, 0) instead of (x - 5)**3*SingularityFunction(x, 5, 0)
|
659 |
+
else:
|
660 |
+
# I don't know how to handle the case for Heaviside expressions
|
661 |
+
# having arguments with more than one variable.
|
662 |
+
raise TypeError(filldedent('''
|
663 |
+
rewrite(SingularityFunction) does not
|
664 |
+
support arguments with more that one variable.'''))
|
venv/lib/python3.10/site-packages/sympy/functions/special/elliptic_integrals.py
ADDED
@@ -0,0 +1,445 @@
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|
|
|
|
|
|
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|
|
|
|
|
|
|
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|
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|
|
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|
|
|
|
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|
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|
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|
|
|
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|
|
|
|
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|
|
|
|
|
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|
|
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|
|
|
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|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
1 |
+
""" Elliptic Integrals. """
|
2 |
+
|
3 |
+
from sympy.core import S, pi, I, Rational
|
4 |
+
from sympy.core.function import Function, ArgumentIndexError
|
5 |
+
from sympy.core.symbol import Dummy
|
6 |
+
from sympy.functions.elementary.complexes import sign
|
7 |
+
from sympy.functions.elementary.hyperbolic import atanh
|
8 |
+
from sympy.functions.elementary.miscellaneous import sqrt
|
9 |
+
from sympy.functions.elementary.trigonometric import sin, tan
|
10 |
+
from sympy.functions.special.gamma_functions import gamma
|
11 |
+
from sympy.functions.special.hyper import hyper, meijerg
|
12 |
+
|
13 |
+
class elliptic_k(Function):
|
14 |
+
r"""
|
15 |
+
The complete elliptic integral of the first kind, defined by
|
16 |
+
|
17 |
+
.. math:: K(m) = F\left(\tfrac{\pi}{2}\middle| m\right)
|
18 |
+
|
19 |
+
where $F\left(z\middle| m\right)$ is the Legendre incomplete
|
20 |
+
elliptic integral of the first kind.
|
21 |
+
|
22 |
+
Explanation
|
23 |
+
===========
|
24 |
+
|
25 |
+
The function $K(m)$ is a single-valued function on the complex
|
26 |
+
plane with branch cut along the interval $(1, \infty)$.
|
27 |
+
|
28 |
+
Note that our notation defines the incomplete elliptic integral
|
29 |
+
in terms of the parameter $m$ instead of the elliptic modulus
|
30 |
+
(eccentricity) $k$.
|
31 |
+
In this case, the parameter $m$ is defined as $m=k^2$.
|
32 |
+
|
33 |
+
Examples
|
34 |
+
========
|
35 |
+
|
36 |
+
>>> from sympy import elliptic_k, I
|
37 |
+
>>> from sympy.abc import m
|
38 |
+
>>> elliptic_k(0)
|
39 |
+
pi/2
|
40 |
+
>>> elliptic_k(1.0 + I)
|
41 |
+
1.50923695405127 + 0.625146415202697*I
|
42 |
+
>>> elliptic_k(m).series(n=3)
|
43 |
+
pi/2 + pi*m/8 + 9*pi*m**2/128 + O(m**3)
|
44 |
+
|
45 |
+
See Also
|
46 |
+
========
|
47 |
+
|
48 |
+
elliptic_f
|
49 |
+
|
50 |
+
References
|
51 |
+
==========
|
52 |
+
|
53 |
+
.. [1] https://en.wikipedia.org/wiki/Elliptic_integrals
|
54 |
+
.. [2] https://functions.wolfram.com/EllipticIntegrals/EllipticK
|
55 |
+
|
56 |
+
"""
|
57 |
+
|
58 |
+
@classmethod
|
59 |
+
def eval(cls, m):
|
60 |
+
if m.is_zero:
|
61 |
+
return pi*S.Half
|
62 |
+
elif m is S.Half:
|
63 |
+
return 8*pi**Rational(3, 2)/gamma(Rational(-1, 4))**2
|
64 |
+
elif m is S.One:
|
65 |
+
return S.ComplexInfinity
|
66 |
+
elif m is S.NegativeOne:
|
67 |
+
return gamma(Rational(1, 4))**2/(4*sqrt(2*pi))
|
68 |
+
elif m in (S.Infinity, S.NegativeInfinity, I*S.Infinity,
|
69 |
+
I*S.NegativeInfinity, S.ComplexInfinity):
|
70 |
+
return S.Zero
|
71 |
+
|
72 |
+
def fdiff(self, argindex=1):
|
73 |
+
m = self.args[0]
|
74 |
+
return (elliptic_e(m) - (1 - m)*elliptic_k(m))/(2*m*(1 - m))
|
75 |
+
|
76 |
+
def _eval_conjugate(self):
|
77 |
+
m = self.args[0]
|
78 |
+
if (m.is_real and (m - 1).is_positive) is False:
|
79 |
+
return self.func(m.conjugate())
|
80 |
+
|
81 |
+
def _eval_nseries(self, x, n, logx, cdir=0):
|
82 |
+
from sympy.simplify import hyperexpand
|
83 |
+
return hyperexpand(self.rewrite(hyper)._eval_nseries(x, n=n, logx=logx))
|
84 |
+
|
85 |
+
def _eval_rewrite_as_hyper(self, m, **kwargs):
|
86 |
+
return pi*S.Half*hyper((S.Half, S.Half), (S.One,), m)
|
87 |
+
|
88 |
+
def _eval_rewrite_as_meijerg(self, m, **kwargs):
|
89 |
+
return meijerg(((S.Half, S.Half), []), ((S.Zero,), (S.Zero,)), -m)/2
|
90 |
+
|
91 |
+
def _eval_is_zero(self):
|
92 |
+
m = self.args[0]
|
93 |
+
if m.is_infinite:
|
94 |
+
return True
|
95 |
+
|
96 |
+
def _eval_rewrite_as_Integral(self, *args):
|
97 |
+
from sympy.integrals.integrals import Integral
|
98 |
+
t = Dummy('t')
|
99 |
+
m = self.args[0]
|
100 |
+
return Integral(1/sqrt(1 - m*sin(t)**2), (t, 0, pi/2))
|
101 |
+
|
102 |
+
|
103 |
+
class elliptic_f(Function):
|
104 |
+
r"""
|
105 |
+
The Legendre incomplete elliptic integral of the first
|
106 |
+
kind, defined by
|
107 |
+
|
108 |
+
.. math:: F\left(z\middle| m\right) =
|
109 |
+
\int_0^z \frac{dt}{\sqrt{1 - m \sin^2 t}}
|
110 |
+
|
111 |
+
Explanation
|
112 |
+
===========
|
113 |
+
|
114 |
+
This function reduces to a complete elliptic integral of
|
115 |
+
the first kind, $K(m)$, when $z = \pi/2$.
|
116 |
+
|
117 |
+
Note that our notation defines the incomplete elliptic integral
|
118 |
+
in terms of the parameter $m$ instead of the elliptic modulus
|
119 |
+
(eccentricity) $k$.
|
120 |
+
In this case, the parameter $m$ is defined as $m=k^2$.
|
121 |
+
|
122 |
+
Examples
|
123 |
+
========
|
124 |
+
|
125 |
+
>>> from sympy import elliptic_f, I
|
126 |
+
>>> from sympy.abc import z, m
|
127 |
+
>>> elliptic_f(z, m).series(z)
|
128 |
+
z + z**5*(3*m**2/40 - m/30) + m*z**3/6 + O(z**6)
|
129 |
+
>>> elliptic_f(3.0 + I/2, 1.0 + I)
|
130 |
+
2.909449841483 + 1.74720545502474*I
|
131 |
+
|
132 |
+
See Also
|
133 |
+
========
|
134 |
+
|
135 |
+
elliptic_k
|
136 |
+
|
137 |
+
References
|
138 |
+
==========
|
139 |
+
|
140 |
+
.. [1] https://en.wikipedia.org/wiki/Elliptic_integrals
|
141 |
+
.. [2] https://functions.wolfram.com/EllipticIntegrals/EllipticF
|
142 |
+
|
143 |
+
"""
|
144 |
+
|
145 |
+
@classmethod
|
146 |
+
def eval(cls, z, m):
|
147 |
+
if z.is_zero:
|
148 |
+
return S.Zero
|
149 |
+
if m.is_zero:
|
150 |
+
return z
|
151 |
+
k = 2*z/pi
|
152 |
+
if k.is_integer:
|
153 |
+
return k*elliptic_k(m)
|
154 |
+
elif m in (S.Infinity, S.NegativeInfinity):
|
155 |
+
return S.Zero
|
156 |
+
elif z.could_extract_minus_sign():
|
157 |
+
return -elliptic_f(-z, m)
|
158 |
+
|
159 |
+
def fdiff(self, argindex=1):
|
160 |
+
z, m = self.args
|
161 |
+
fm = sqrt(1 - m*sin(z)**2)
|
162 |
+
if argindex == 1:
|
163 |
+
return 1/fm
|
164 |
+
elif argindex == 2:
|
165 |
+
return (elliptic_e(z, m)/(2*m*(1 - m)) - elliptic_f(z, m)/(2*m) -
|
166 |
+
sin(2*z)/(4*(1 - m)*fm))
|
167 |
+
raise ArgumentIndexError(self, argindex)
|
168 |
+
|
169 |
+
def _eval_conjugate(self):
|
170 |
+
z, m = self.args
|
171 |
+
if (m.is_real and (m - 1).is_positive) is False:
|
172 |
+
return self.func(z.conjugate(), m.conjugate())
|
173 |
+
|
174 |
+
def _eval_rewrite_as_Integral(self, *args):
|
175 |
+
from sympy.integrals.integrals import Integral
|
176 |
+
t = Dummy('t')
|
177 |
+
z, m = self.args[0], self.args[1]
|
178 |
+
return Integral(1/(sqrt(1 - m*sin(t)**2)), (t, 0, z))
|
179 |
+
|
180 |
+
def _eval_is_zero(self):
|
181 |
+
z, m = self.args
|
182 |
+
if z.is_zero:
|
183 |
+
return True
|
184 |
+
if m.is_extended_real and m.is_infinite:
|
185 |
+
return True
|
186 |
+
|
187 |
+
|
188 |
+
class elliptic_e(Function):
|
189 |
+
r"""
|
190 |
+
Called with two arguments $z$ and $m$, evaluates the
|
191 |
+
incomplete elliptic integral of the second kind, defined by
|
192 |
+
|
193 |
+
.. math:: E\left(z\middle| m\right) = \int_0^z \sqrt{1 - m \sin^2 t} dt
|
194 |
+
|
195 |
+
Called with a single argument $m$, evaluates the Legendre complete
|
196 |
+
elliptic integral of the second kind
|
197 |
+
|
198 |
+
.. math:: E(m) = E\left(\tfrac{\pi}{2}\middle| m\right)
|
199 |
+
|
200 |
+
Explanation
|
201 |
+
===========
|
202 |
+
|
203 |
+
The function $E(m)$ is a single-valued function on the complex
|
204 |
+
plane with branch cut along the interval $(1, \infty)$.
|
205 |
+
|
206 |
+
Note that our notation defines the incomplete elliptic integral
|
207 |
+
in terms of the parameter $m$ instead of the elliptic modulus
|
208 |
+
(eccentricity) $k$.
|
209 |
+
In this case, the parameter $m$ is defined as $m=k^2$.
|
210 |
+
|
211 |
+
Examples
|
212 |
+
========
|
213 |
+
|
214 |
+
>>> from sympy import elliptic_e, I
|
215 |
+
>>> from sympy.abc import z, m
|
216 |
+
>>> elliptic_e(z, m).series(z)
|
217 |
+
z + z**5*(-m**2/40 + m/30) - m*z**3/6 + O(z**6)
|
218 |
+
>>> elliptic_e(m).series(n=4)
|
219 |
+
pi/2 - pi*m/8 - 3*pi*m**2/128 - 5*pi*m**3/512 + O(m**4)
|
220 |
+
>>> elliptic_e(1 + I, 2 - I/2).n()
|
221 |
+
1.55203744279187 + 0.290764986058437*I
|
222 |
+
>>> elliptic_e(0)
|
223 |
+
pi/2
|
224 |
+
>>> elliptic_e(2.0 - I)
|
225 |
+
0.991052601328069 + 0.81879421395609*I
|
226 |
+
|
227 |
+
References
|
228 |
+
==========
|
229 |
+
|
230 |
+
.. [1] https://en.wikipedia.org/wiki/Elliptic_integrals
|
231 |
+
.. [2] https://functions.wolfram.com/EllipticIntegrals/EllipticE2
|
232 |
+
.. [3] https://functions.wolfram.com/EllipticIntegrals/EllipticE
|
233 |
+
|
234 |
+
"""
|
235 |
+
|
236 |
+
@classmethod
|
237 |
+
def eval(cls, m, z=None):
|
238 |
+
if z is not None:
|
239 |
+
z, m = m, z
|
240 |
+
k = 2*z/pi
|
241 |
+
if m.is_zero:
|
242 |
+
return z
|
243 |
+
if z.is_zero:
|
244 |
+
return S.Zero
|
245 |
+
elif k.is_integer:
|
246 |
+
return k*elliptic_e(m)
|
247 |
+
elif m in (S.Infinity, S.NegativeInfinity):
|
248 |
+
return S.ComplexInfinity
|
249 |
+
elif z.could_extract_minus_sign():
|
250 |
+
return -elliptic_e(-z, m)
|
251 |
+
else:
|
252 |
+
if m.is_zero:
|
253 |
+
return pi/2
|
254 |
+
elif m is S.One:
|
255 |
+
return S.One
|
256 |
+
elif m is S.Infinity:
|
257 |
+
return I*S.Infinity
|
258 |
+
elif m is S.NegativeInfinity:
|
259 |
+
return S.Infinity
|
260 |
+
elif m is S.ComplexInfinity:
|
261 |
+
return S.ComplexInfinity
|
262 |
+
|
263 |
+
def fdiff(self, argindex=1):
|
264 |
+
if len(self.args) == 2:
|
265 |
+
z, m = self.args
|
266 |
+
if argindex == 1:
|
267 |
+
return sqrt(1 - m*sin(z)**2)
|
268 |
+
elif argindex == 2:
|
269 |
+
return (elliptic_e(z, m) - elliptic_f(z, m))/(2*m)
|
270 |
+
else:
|
271 |
+
m = self.args[0]
|
272 |
+
if argindex == 1:
|
273 |
+
return (elliptic_e(m) - elliptic_k(m))/(2*m)
|
274 |
+
raise ArgumentIndexError(self, argindex)
|
275 |
+
|
276 |
+
def _eval_conjugate(self):
|
277 |
+
if len(self.args) == 2:
|
278 |
+
z, m = self.args
|
279 |
+
if (m.is_real and (m - 1).is_positive) is False:
|
280 |
+
return self.func(z.conjugate(), m.conjugate())
|
281 |
+
else:
|
282 |
+
m = self.args[0]
|
283 |
+
if (m.is_real and (m - 1).is_positive) is False:
|
284 |
+
return self.func(m.conjugate())
|
285 |
+
|
286 |
+
def _eval_nseries(self, x, n, logx, cdir=0):
|
287 |
+
from sympy.simplify import hyperexpand
|
288 |
+
if len(self.args) == 1:
|
289 |
+
return hyperexpand(self.rewrite(hyper)._eval_nseries(x, n=n, logx=logx))
|
290 |
+
return super()._eval_nseries(x, n=n, logx=logx)
|
291 |
+
|
292 |
+
def _eval_rewrite_as_hyper(self, *args, **kwargs):
|
293 |
+
if len(args) == 1:
|
294 |
+
m = args[0]
|
295 |
+
return (pi/2)*hyper((Rational(-1, 2), S.Half), (S.One,), m)
|
296 |
+
|
297 |
+
def _eval_rewrite_as_meijerg(self, *args, **kwargs):
|
298 |
+
if len(args) == 1:
|
299 |
+
m = args[0]
|
300 |
+
return -meijerg(((S.Half, Rational(3, 2)), []), \
|
301 |
+
((S.Zero,), (S.Zero,)), -m)/4
|
302 |
+
|
303 |
+
def _eval_rewrite_as_Integral(self, *args):
|
304 |
+
from sympy.integrals.integrals import Integral
|
305 |
+
z, m = (pi/2, self.args[0]) if len(self.args) == 1 else self.args
|
306 |
+
t = Dummy('t')
|
307 |
+
return Integral(sqrt(1 - m*sin(t)**2), (t, 0, z))
|
308 |
+
|
309 |
+
|
310 |
+
class elliptic_pi(Function):
|
311 |
+
r"""
|
312 |
+
Called with three arguments $n$, $z$ and $m$, evaluates the
|
313 |
+
Legendre incomplete elliptic integral of the third kind, defined by
|
314 |
+
|
315 |
+
.. math:: \Pi\left(n; z\middle| m\right) = \int_0^z \frac{dt}
|
316 |
+
{\left(1 - n \sin^2 t\right) \sqrt{1 - m \sin^2 t}}
|
317 |
+
|
318 |
+
Called with two arguments $n$ and $m$, evaluates the complete
|
319 |
+
elliptic integral of the third kind:
|
320 |
+
|
321 |
+
.. math:: \Pi\left(n\middle| m\right) =
|
322 |
+
\Pi\left(n; \tfrac{\pi}{2}\middle| m\right)
|
323 |
+
|
324 |
+
Explanation
|
325 |
+
===========
|
326 |
+
|
327 |
+
Note that our notation defines the incomplete elliptic integral
|
328 |
+
in terms of the parameter $m$ instead of the elliptic modulus
|
329 |
+
(eccentricity) $k$.
|
330 |
+
In this case, the parameter $m$ is defined as $m=k^2$.
|
331 |
+
|
332 |
+
Examples
|
333 |
+
========
|
334 |
+
|
335 |
+
>>> from sympy import elliptic_pi, I
|
336 |
+
>>> from sympy.abc import z, n, m
|
337 |
+
>>> elliptic_pi(n, z, m).series(z, n=4)
|
338 |
+
z + z**3*(m/6 + n/3) + O(z**4)
|
339 |
+
>>> elliptic_pi(0.5 + I, 1.0 - I, 1.2)
|
340 |
+
2.50232379629182 - 0.760939574180767*I
|
341 |
+
>>> elliptic_pi(0, 0)
|
342 |
+
pi/2
|
343 |
+
>>> elliptic_pi(1.0 - I/3, 2.0 + I)
|
344 |
+
3.29136443417283 + 0.32555634906645*I
|
345 |
+
|
346 |
+
References
|
347 |
+
==========
|
348 |
+
|
349 |
+
.. [1] https://en.wikipedia.org/wiki/Elliptic_integrals
|
350 |
+
.. [2] https://functions.wolfram.com/EllipticIntegrals/EllipticPi3
|
351 |
+
.. [3] https://functions.wolfram.com/EllipticIntegrals/EllipticPi
|
352 |
+
|
353 |
+
"""
|
354 |
+
|
355 |
+
@classmethod
|
356 |
+
def eval(cls, n, m, z=None):
|
357 |
+
if z is not None:
|
358 |
+
n, z, m = n, m, z
|
359 |
+
if n.is_zero:
|
360 |
+
return elliptic_f(z, m)
|
361 |
+
elif n is S.One:
|
362 |
+
return (elliptic_f(z, m) +
|
363 |
+
(sqrt(1 - m*sin(z)**2)*tan(z) -
|
364 |
+
elliptic_e(z, m))/(1 - m))
|
365 |
+
k = 2*z/pi
|
366 |
+
if k.is_integer:
|
367 |
+
return k*elliptic_pi(n, m)
|
368 |
+
elif m.is_zero:
|
369 |
+
return atanh(sqrt(n - 1)*tan(z))/sqrt(n - 1)
|
370 |
+
elif n == m:
|
371 |
+
return (elliptic_f(z, n) - elliptic_pi(1, z, n) +
|
372 |
+
tan(z)/sqrt(1 - n*sin(z)**2))
|
373 |
+
elif n in (S.Infinity, S.NegativeInfinity):
|
374 |
+
return S.Zero
|
375 |
+
elif m in (S.Infinity, S.NegativeInfinity):
|
376 |
+
return S.Zero
|
377 |
+
elif z.could_extract_minus_sign():
|
378 |
+
return -elliptic_pi(n, -z, m)
|
379 |
+
if n.is_zero:
|
380 |
+
return elliptic_f(z, m)
|
381 |
+
if m.is_extended_real and m.is_infinite or \
|
382 |
+
n.is_extended_real and n.is_infinite:
|
383 |
+
return S.Zero
|
384 |
+
else:
|
385 |
+
if n.is_zero:
|
386 |
+
return elliptic_k(m)
|
387 |
+
elif n is S.One:
|
388 |
+
return S.ComplexInfinity
|
389 |
+
elif m.is_zero:
|
390 |
+
return pi/(2*sqrt(1 - n))
|
391 |
+
elif m == S.One:
|
392 |
+
return S.NegativeInfinity/sign(n - 1)
|
393 |
+
elif n == m:
|
394 |
+
return elliptic_e(n)/(1 - n)
|
395 |
+
elif n in (S.Infinity, S.NegativeInfinity):
|
396 |
+
return S.Zero
|
397 |
+
elif m in (S.Infinity, S.NegativeInfinity):
|
398 |
+
return S.Zero
|
399 |
+
if n.is_zero:
|
400 |
+
return elliptic_k(m)
|
401 |
+
if m.is_extended_real and m.is_infinite or \
|
402 |
+
n.is_extended_real and n.is_infinite:
|
403 |
+
return S.Zero
|
404 |
+
|
405 |
+
def _eval_conjugate(self):
|
406 |
+
if len(self.args) == 3:
|
407 |
+
n, z, m = self.args
|
408 |
+
if (n.is_real and (n - 1).is_positive) is False and \
|
409 |
+
(m.is_real and (m - 1).is_positive) is False:
|
410 |
+
return self.func(n.conjugate(), z.conjugate(), m.conjugate())
|
411 |
+
else:
|
412 |
+
n, m = self.args
|
413 |
+
return self.func(n.conjugate(), m.conjugate())
|
414 |
+
|
415 |
+
def fdiff(self, argindex=1):
|
416 |
+
if len(self.args) == 3:
|
417 |
+
n, z, m = self.args
|
418 |
+
fm, fn = sqrt(1 - m*sin(z)**2), 1 - n*sin(z)**2
|
419 |
+
if argindex == 1:
|
420 |
+
return (elliptic_e(z, m) + (m - n)*elliptic_f(z, m)/n +
|
421 |
+
(n**2 - m)*elliptic_pi(n, z, m)/n -
|
422 |
+
n*fm*sin(2*z)/(2*fn))/(2*(m - n)*(n - 1))
|
423 |
+
elif argindex == 2:
|
424 |
+
return 1/(fm*fn)
|
425 |
+
elif argindex == 3:
|
426 |
+
return (elliptic_e(z, m)/(m - 1) +
|
427 |
+
elliptic_pi(n, z, m) -
|
428 |
+
m*sin(2*z)/(2*(m - 1)*fm))/(2*(n - m))
|
429 |
+
else:
|
430 |
+
n, m = self.args
|
431 |
+
if argindex == 1:
|
432 |
+
return (elliptic_e(m) + (m - n)*elliptic_k(m)/n +
|
433 |
+
(n**2 - m)*elliptic_pi(n, m)/n)/(2*(m - n)*(n - 1))
|
434 |
+
elif argindex == 2:
|
435 |
+
return (elliptic_e(m)/(m - 1) + elliptic_pi(n, m))/(2*(n - m))
|
436 |
+
raise ArgumentIndexError(self, argindex)
|
437 |
+
|
438 |
+
def _eval_rewrite_as_Integral(self, *args):
|
439 |
+
from sympy.integrals.integrals import Integral
|
440 |
+
if len(self.args) == 2:
|
441 |
+
n, m, z = self.args[0], self.args[1], pi/2
|
442 |
+
else:
|
443 |
+
n, z, m = self.args
|
444 |
+
t = Dummy('t')
|
445 |
+
return Integral(1/((1 - n*sin(t)**2)*sqrt(1 - m*sin(t)**2)), (t, 0, z))
|
venv/lib/python3.10/site-packages/sympy/functions/special/error_functions.py
ADDED
@@ -0,0 +1,2741 @@
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|
|
1 |
+
""" This module contains various functions that are special cases
|
2 |
+
of incomplete gamma functions. It should probably be renamed. """
|
3 |
+
|
4 |
+
from sympy.core import EulerGamma # Must be imported from core, not core.numbers
|
5 |
+
from sympy.core.add import Add
|
6 |
+
from sympy.core.cache import cacheit
|
7 |
+
from sympy.core.function import Function, ArgumentIndexError, expand_mul
|
8 |
+
from sympy.core.numbers import I, pi, Rational
|
9 |
+
from sympy.core.relational import is_eq
|
10 |
+
from sympy.core.power import Pow
|
11 |
+
from sympy.core.singleton import S
|
12 |
+
from sympy.core.symbol import Symbol
|
13 |
+
from sympy.core.sympify import sympify
|
14 |
+
from sympy.functions.combinatorial.factorials import factorial, factorial2, RisingFactorial
|
15 |
+
from sympy.functions.elementary.complexes import polar_lift, re, unpolarify
|
16 |
+
from sympy.functions.elementary.integers import ceiling, floor
|
17 |
+
from sympy.functions.elementary.miscellaneous import sqrt, root
|
18 |
+
from sympy.functions.elementary.exponential import exp, log, exp_polar
|
19 |
+
from sympy.functions.elementary.hyperbolic import cosh, sinh
|
20 |
+
from sympy.functions.elementary.trigonometric import cos, sin, sinc
|
21 |
+
from sympy.functions.special.hyper import hyper, meijerg
|
22 |
+
|
23 |
+
# TODO series expansions
|
24 |
+
# TODO see the "Note:" in Ei
|
25 |
+
|
26 |
+
# Helper function
|
27 |
+
def real_to_real_as_real_imag(self, deep=True, **hints):
|
28 |
+
if self.args[0].is_extended_real:
|
29 |
+
if deep:
|
30 |
+
hints['complex'] = False
|
31 |
+
return (self.expand(deep, **hints), S.Zero)
|
32 |
+
else:
|
33 |
+
return (self, S.Zero)
|
34 |
+
if deep:
|
35 |
+
x, y = self.args[0].expand(deep, **hints).as_real_imag()
|
36 |
+
else:
|
37 |
+
x, y = self.args[0].as_real_imag()
|
38 |
+
re = (self.func(x + I*y) + self.func(x - I*y))/2
|
39 |
+
im = (self.func(x + I*y) - self.func(x - I*y))/(2*I)
|
40 |
+
return (re, im)
|
41 |
+
|
42 |
+
|
43 |
+
###############################################################################
|
44 |
+
################################ ERROR FUNCTION ###############################
|
45 |
+
###############################################################################
|
46 |
+
|
47 |
+
|
48 |
+
class erf(Function):
|
49 |
+
r"""
|
50 |
+
The Gauss error function.
|
51 |
+
|
52 |
+
Explanation
|
53 |
+
===========
|
54 |
+
|
55 |
+
This function is defined as:
|
56 |
+
|
57 |
+
.. math ::
|
58 |
+
\mathrm{erf}(x) = \frac{2}{\sqrt{\pi}} \int_0^x e^{-t^2} \mathrm{d}t.
|
59 |
+
|
60 |
+
Examples
|
61 |
+
========
|
62 |
+
|
63 |
+
>>> from sympy import I, oo, erf
|
64 |
+
>>> from sympy.abc import z
|
65 |
+
|
66 |
+
Several special values are known:
|
67 |
+
|
68 |
+
>>> erf(0)
|
69 |
+
0
|
70 |
+
>>> erf(oo)
|
71 |
+
1
|
72 |
+
>>> erf(-oo)
|
73 |
+
-1
|
74 |
+
>>> erf(I*oo)
|
75 |
+
oo*I
|
76 |
+
>>> erf(-I*oo)
|
77 |
+
-oo*I
|
78 |
+
|
79 |
+
In general one can pull out factors of -1 and $I$ from the argument:
|
80 |
+
|
81 |
+
>>> erf(-z)
|
82 |
+
-erf(z)
|
83 |
+
|
84 |
+
The error function obeys the mirror symmetry:
|
85 |
+
|
86 |
+
>>> from sympy import conjugate
|
87 |
+
>>> conjugate(erf(z))
|
88 |
+
erf(conjugate(z))
|
89 |
+
|
90 |
+
Differentiation with respect to $z$ is supported:
|
91 |
+
|
92 |
+
>>> from sympy import diff
|
93 |
+
>>> diff(erf(z), z)
|
94 |
+
2*exp(-z**2)/sqrt(pi)
|
95 |
+
|
96 |
+
We can numerically evaluate the error function to arbitrary precision
|
97 |
+
on the whole complex plane:
|
98 |
+
|
99 |
+
>>> erf(4).evalf(30)
|
100 |
+
0.999999984582742099719981147840
|
101 |
+
|
102 |
+
>>> erf(-4*I).evalf(30)
|
103 |
+
-1296959.73071763923152794095062*I
|
104 |
+
|
105 |
+
See Also
|
106 |
+
========
|
107 |
+
|
108 |
+
erfc: Complementary error function.
|
109 |
+
erfi: Imaginary error function.
|
110 |
+
erf2: Two-argument error function.
|
111 |
+
erfinv: Inverse error function.
|
112 |
+
erfcinv: Inverse Complementary error function.
|
113 |
+
erf2inv: Inverse two-argument error function.
|
114 |
+
|
115 |
+
References
|
116 |
+
==========
|
117 |
+
|
118 |
+
.. [1] https://en.wikipedia.org/wiki/Error_function
|
119 |
+
.. [2] https://dlmf.nist.gov/7
|
120 |
+
.. [3] https://mathworld.wolfram.com/Erf.html
|
121 |
+
.. [4] https://functions.wolfram.com/GammaBetaErf/Erf
|
122 |
+
|
123 |
+
"""
|
124 |
+
|
125 |
+
unbranched = True
|
126 |
+
|
127 |
+
def fdiff(self, argindex=1):
|
128 |
+
if argindex == 1:
|
129 |
+
return 2*exp(-self.args[0]**2)/sqrt(pi)
|
130 |
+
else:
|
131 |
+
raise ArgumentIndexError(self, argindex)
|
132 |
+
|
133 |
+
|
134 |
+
def inverse(self, argindex=1):
|
135 |
+
"""
|
136 |
+
Returns the inverse of this function.
|
137 |
+
|
138 |
+
"""
|
139 |
+
return erfinv
|
140 |
+
|
141 |
+
@classmethod
|
142 |
+
def eval(cls, arg):
|
143 |
+
if arg.is_Number:
|
144 |
+
if arg is S.NaN:
|
145 |
+
return S.NaN
|
146 |
+
elif arg is S.Infinity:
|
147 |
+
return S.One
|
148 |
+
elif arg is S.NegativeInfinity:
|
149 |
+
return S.NegativeOne
|
150 |
+
elif arg.is_zero:
|
151 |
+
return S.Zero
|
152 |
+
|
153 |
+
if isinstance(arg, erfinv):
|
154 |
+
return arg.args[0]
|
155 |
+
|
156 |
+
if isinstance(arg, erfcinv):
|
157 |
+
return S.One - arg.args[0]
|
158 |
+
|
159 |
+
if arg.is_zero:
|
160 |
+
return S.Zero
|
161 |
+
|
162 |
+
# Only happens with unevaluated erf2inv
|
163 |
+
if isinstance(arg, erf2inv) and arg.args[0].is_zero:
|
164 |
+
return arg.args[1]
|
165 |
+
|
166 |
+
# Try to pull out factors of I
|
167 |
+
t = arg.extract_multiplicatively(I)
|
168 |
+
if t in (S.Infinity, S.NegativeInfinity):
|
169 |
+
return arg
|
170 |
+
|
171 |
+
# Try to pull out factors of -1
|
172 |
+
if arg.could_extract_minus_sign():
|
173 |
+
return -cls(-arg)
|
174 |
+
|
175 |
+
@staticmethod
|
176 |
+
@cacheit
|
177 |
+
def taylor_term(n, x, *previous_terms):
|
178 |
+
if n < 0 or n % 2 == 0:
|
179 |
+
return S.Zero
|
180 |
+
else:
|
181 |
+
x = sympify(x)
|
182 |
+
k = floor((n - 1)/S(2))
|
183 |
+
if len(previous_terms) > 2:
|
184 |
+
return -previous_terms[-2] * x**2 * (n - 2)/(n*k)
|
185 |
+
else:
|
186 |
+
return 2*S.NegativeOne**k * x**n/(n*factorial(k)*sqrt(pi))
|
187 |
+
|
188 |
+
def _eval_conjugate(self):
|
189 |
+
return self.func(self.args[0].conjugate())
|
190 |
+
|
191 |
+
def _eval_is_real(self):
|
192 |
+
return self.args[0].is_extended_real
|
193 |
+
|
194 |
+
def _eval_is_finite(self):
|
195 |
+
if self.args[0].is_finite:
|
196 |
+
return True
|
197 |
+
else:
|
198 |
+
return self.args[0].is_extended_real
|
199 |
+
|
200 |
+
def _eval_is_zero(self):
|
201 |
+
return self.args[0].is_zero
|
202 |
+
|
203 |
+
def _eval_rewrite_as_uppergamma(self, z, **kwargs):
|
204 |
+
from sympy.functions.special.gamma_functions import uppergamma
|
205 |
+
return sqrt(z**2)/z*(S.One - uppergamma(S.Half, z**2)/sqrt(pi))
|
206 |
+
|
207 |
+
def _eval_rewrite_as_fresnels(self, z, **kwargs):
|
208 |
+
arg = (S.One - I)*z/sqrt(pi)
|
209 |
+
return (S.One + I)*(fresnelc(arg) - I*fresnels(arg))
|
210 |
+
|
211 |
+
def _eval_rewrite_as_fresnelc(self, z, **kwargs):
|
212 |
+
arg = (S.One - I)*z/sqrt(pi)
|
213 |
+
return (S.One + I)*(fresnelc(arg) - I*fresnels(arg))
|
214 |
+
|
215 |
+
def _eval_rewrite_as_meijerg(self, z, **kwargs):
|
216 |
+
return z/sqrt(pi)*meijerg([S.Half], [], [0], [Rational(-1, 2)], z**2)
|
217 |
+
|
218 |
+
def _eval_rewrite_as_hyper(self, z, **kwargs):
|
219 |
+
return 2*z/sqrt(pi)*hyper([S.Half], [3*S.Half], -z**2)
|
220 |
+
|
221 |
+
def _eval_rewrite_as_expint(self, z, **kwargs):
|
222 |
+
return sqrt(z**2)/z - z*expint(S.Half, z**2)/sqrt(pi)
|
223 |
+
|
224 |
+
def _eval_rewrite_as_tractable(self, z, limitvar=None, **kwargs):
|
225 |
+
from sympy.series.limits import limit
|
226 |
+
if limitvar:
|
227 |
+
lim = limit(z, limitvar, S.Infinity)
|
228 |
+
if lim is S.NegativeInfinity:
|
229 |
+
return S.NegativeOne + _erfs(-z)*exp(-z**2)
|
230 |
+
return S.One - _erfs(z)*exp(-z**2)
|
231 |
+
|
232 |
+
def _eval_rewrite_as_erfc(self, z, **kwargs):
|
233 |
+
return S.One - erfc(z)
|
234 |
+
|
235 |
+
def _eval_rewrite_as_erfi(self, z, **kwargs):
|
236 |
+
return -I*erfi(I*z)
|
237 |
+
|
238 |
+
def _eval_as_leading_term(self, x, logx=None, cdir=0):
|
239 |
+
arg = self.args[0].as_leading_term(x, logx=logx, cdir=cdir)
|
240 |
+
arg0 = arg.subs(x, 0)
|
241 |
+
|
242 |
+
if arg0 is S.ComplexInfinity:
|
243 |
+
arg0 = arg.limit(x, 0, dir='-' if cdir == -1 else '+')
|
244 |
+
if x in arg.free_symbols and arg0.is_zero:
|
245 |
+
return 2*arg/sqrt(pi)
|
246 |
+
else:
|
247 |
+
return self.func(arg0)
|
248 |
+
|
249 |
+
def _eval_aseries(self, n, args0, x, logx):
|
250 |
+
from sympy.series.order import Order
|
251 |
+
point = args0[0]
|
252 |
+
|
253 |
+
if point in [S.Infinity, S.NegativeInfinity]:
|
254 |
+
z = self.args[0]
|
255 |
+
|
256 |
+
try:
|
257 |
+
_, ex = z.leadterm(x)
|
258 |
+
except (ValueError, NotImplementedError):
|
259 |
+
return self
|
260 |
+
|
261 |
+
ex = -ex # as x->1/x for aseries
|
262 |
+
if ex.is_positive:
|
263 |
+
newn = ceiling(n/ex)
|
264 |
+
s = [S.NegativeOne**k * factorial2(2*k - 1) / (z**(2*k + 1) * 2**k)
|
265 |
+
for k in range(newn)] + [Order(1/z**newn, x)]
|
266 |
+
return S.One - (exp(-z**2)/sqrt(pi)) * Add(*s)
|
267 |
+
|
268 |
+
return super(erf, self)._eval_aseries(n, args0, x, logx)
|
269 |
+
|
270 |
+
as_real_imag = real_to_real_as_real_imag
|
271 |
+
|
272 |
+
|
273 |
+
class erfc(Function):
|
274 |
+
r"""
|
275 |
+
Complementary Error Function.
|
276 |
+
|
277 |
+
Explanation
|
278 |
+
===========
|
279 |
+
|
280 |
+
The function is defined as:
|
281 |
+
|
282 |
+
.. math ::
|
283 |
+
\mathrm{erfc}(x) = \frac{2}{\sqrt{\pi}} \int_x^\infty e^{-t^2} \mathrm{d}t
|
284 |
+
|
285 |
+
Examples
|
286 |
+
========
|
287 |
+
|
288 |
+
>>> from sympy import I, oo, erfc
|
289 |
+
>>> from sympy.abc import z
|
290 |
+
|
291 |
+
Several special values are known:
|
292 |
+
|
293 |
+
>>> erfc(0)
|
294 |
+
1
|
295 |
+
>>> erfc(oo)
|
296 |
+
0
|
297 |
+
>>> erfc(-oo)
|
298 |
+
2
|
299 |
+
>>> erfc(I*oo)
|
300 |
+
-oo*I
|
301 |
+
>>> erfc(-I*oo)
|
302 |
+
oo*I
|
303 |
+
|
304 |
+
The error function obeys the mirror symmetry:
|
305 |
+
|
306 |
+
>>> from sympy import conjugate
|
307 |
+
>>> conjugate(erfc(z))
|
308 |
+
erfc(conjugate(z))
|
309 |
+
|
310 |
+
Differentiation with respect to $z$ is supported:
|
311 |
+
|
312 |
+
>>> from sympy import diff
|
313 |
+
>>> diff(erfc(z), z)
|
314 |
+
-2*exp(-z**2)/sqrt(pi)
|
315 |
+
|
316 |
+
It also follows
|
317 |
+
|
318 |
+
>>> erfc(-z)
|
319 |
+
2 - erfc(z)
|
320 |
+
|
321 |
+
We can numerically evaluate the complementary error function to arbitrary
|
322 |
+
precision on the whole complex plane:
|
323 |
+
|
324 |
+
>>> erfc(4).evalf(30)
|
325 |
+
0.0000000154172579002800188521596734869
|
326 |
+
|
327 |
+
>>> erfc(4*I).evalf(30)
|
328 |
+
1.0 - 1296959.73071763923152794095062*I
|
329 |
+
|
330 |
+
See Also
|
331 |
+
========
|
332 |
+
|
333 |
+
erf: Gaussian error function.
|
334 |
+
erfi: Imaginary error function.
|
335 |
+
erf2: Two-argument error function.
|
336 |
+
erfinv: Inverse error function.
|
337 |
+
erfcinv: Inverse Complementary error function.
|
338 |
+
erf2inv: Inverse two-argument error function.
|
339 |
+
|
340 |
+
References
|
341 |
+
==========
|
342 |
+
|
343 |
+
.. [1] https://en.wikipedia.org/wiki/Error_function
|
344 |
+
.. [2] https://dlmf.nist.gov/7
|
345 |
+
.. [3] https://mathworld.wolfram.com/Erfc.html
|
346 |
+
.. [4] https://functions.wolfram.com/GammaBetaErf/Erfc
|
347 |
+
|
348 |
+
"""
|
349 |
+
|
350 |
+
unbranched = True
|
351 |
+
|
352 |
+
def fdiff(self, argindex=1):
|
353 |
+
if argindex == 1:
|
354 |
+
return -2*exp(-self.args[0]**2)/sqrt(pi)
|
355 |
+
else:
|
356 |
+
raise ArgumentIndexError(self, argindex)
|
357 |
+
|
358 |
+
def inverse(self, argindex=1):
|
359 |
+
"""
|
360 |
+
Returns the inverse of this function.
|
361 |
+
|
362 |
+
"""
|
363 |
+
return erfcinv
|
364 |
+
|
365 |
+
@classmethod
|
366 |
+
def eval(cls, arg):
|
367 |
+
if arg.is_Number:
|
368 |
+
if arg is S.NaN:
|
369 |
+
return S.NaN
|
370 |
+
elif arg is S.Infinity:
|
371 |
+
return S.Zero
|
372 |
+
elif arg.is_zero:
|
373 |
+
return S.One
|
374 |
+
|
375 |
+
if isinstance(arg, erfinv):
|
376 |
+
return S.One - arg.args[0]
|
377 |
+
|
378 |
+
if isinstance(arg, erfcinv):
|
379 |
+
return arg.args[0]
|
380 |
+
|
381 |
+
if arg.is_zero:
|
382 |
+
return S.One
|
383 |
+
|
384 |
+
# Try to pull out factors of I
|
385 |
+
t = arg.extract_multiplicatively(I)
|
386 |
+
if t in (S.Infinity, S.NegativeInfinity):
|
387 |
+
return -arg
|
388 |
+
|
389 |
+
# Try to pull out factors of -1
|
390 |
+
if arg.could_extract_minus_sign():
|
391 |
+
return 2 - cls(-arg)
|
392 |
+
|
393 |
+
@staticmethod
|
394 |
+
@cacheit
|
395 |
+
def taylor_term(n, x, *previous_terms):
|
396 |
+
if n == 0:
|
397 |
+
return S.One
|
398 |
+
elif n < 0 or n % 2 == 0:
|
399 |
+
return S.Zero
|
400 |
+
else:
|
401 |
+
x = sympify(x)
|
402 |
+
k = floor((n - 1)/S(2))
|
403 |
+
if len(previous_terms) > 2:
|
404 |
+
return -previous_terms[-2] * x**2 * (n - 2)/(n*k)
|
405 |
+
else:
|
406 |
+
return -2*S.NegativeOne**k * x**n/(n*factorial(k)*sqrt(pi))
|
407 |
+
|
408 |
+
def _eval_conjugate(self):
|
409 |
+
return self.func(self.args[0].conjugate())
|
410 |
+
|
411 |
+
def _eval_is_real(self):
|
412 |
+
return self.args[0].is_extended_real
|
413 |
+
|
414 |
+
def _eval_rewrite_as_tractable(self, z, limitvar=None, **kwargs):
|
415 |
+
return self.rewrite(erf).rewrite("tractable", deep=True, limitvar=limitvar)
|
416 |
+
|
417 |
+
def _eval_rewrite_as_erf(self, z, **kwargs):
|
418 |
+
return S.One - erf(z)
|
419 |
+
|
420 |
+
def _eval_rewrite_as_erfi(self, z, **kwargs):
|
421 |
+
return S.One + I*erfi(I*z)
|
422 |
+
|
423 |
+
def _eval_rewrite_as_fresnels(self, z, **kwargs):
|
424 |
+
arg = (S.One - I)*z/sqrt(pi)
|
425 |
+
return S.One - (S.One + I)*(fresnelc(arg) - I*fresnels(arg))
|
426 |
+
|
427 |
+
def _eval_rewrite_as_fresnelc(self, z, **kwargs):
|
428 |
+
arg = (S.One-I)*z/sqrt(pi)
|
429 |
+
return S.One - (S.One + I)*(fresnelc(arg) - I*fresnels(arg))
|
430 |
+
|
431 |
+
def _eval_rewrite_as_meijerg(self, z, **kwargs):
|
432 |
+
return S.One - z/sqrt(pi)*meijerg([S.Half], [], [0], [Rational(-1, 2)], z**2)
|
433 |
+
|
434 |
+
def _eval_rewrite_as_hyper(self, z, **kwargs):
|
435 |
+
return S.One - 2*z/sqrt(pi)*hyper([S.Half], [3*S.Half], -z**2)
|
436 |
+
|
437 |
+
def _eval_rewrite_as_uppergamma(self, z, **kwargs):
|
438 |
+
from sympy.functions.special.gamma_functions import uppergamma
|
439 |
+
return S.One - sqrt(z**2)/z*(S.One - uppergamma(S.Half, z**2)/sqrt(pi))
|
440 |
+
|
441 |
+
def _eval_rewrite_as_expint(self, z, **kwargs):
|
442 |
+
return S.One - sqrt(z**2)/z + z*expint(S.Half, z**2)/sqrt(pi)
|
443 |
+
|
444 |
+
def _eval_expand_func(self, **hints):
|
445 |
+
return self.rewrite(erf)
|
446 |
+
|
447 |
+
def _eval_as_leading_term(self, x, logx=None, cdir=0):
|
448 |
+
arg = self.args[0].as_leading_term(x, logx=logx, cdir=cdir)
|
449 |
+
arg0 = arg.subs(x, 0)
|
450 |
+
|
451 |
+
if arg0 is S.ComplexInfinity:
|
452 |
+
arg0 = arg.limit(x, 0, dir='-' if cdir == -1 else '+')
|
453 |
+
if arg0.is_zero:
|
454 |
+
return S.One
|
455 |
+
else:
|
456 |
+
return self.func(arg0)
|
457 |
+
|
458 |
+
as_real_imag = real_to_real_as_real_imag
|
459 |
+
|
460 |
+
def _eval_aseries(self, n, args0, x, logx):
|
461 |
+
return S.One - erf(*self.args)._eval_aseries(n, args0, x, logx)
|
462 |
+
|
463 |
+
|
464 |
+
class erfi(Function):
|
465 |
+
r"""
|
466 |
+
Imaginary error function.
|
467 |
+
|
468 |
+
Explanation
|
469 |
+
===========
|
470 |
+
|
471 |
+
The function erfi is defined as:
|
472 |
+
|
473 |
+
.. math ::
|
474 |
+
\mathrm{erfi}(x) = \frac{2}{\sqrt{\pi}} \int_0^x e^{t^2} \mathrm{d}t
|
475 |
+
|
476 |
+
Examples
|
477 |
+
========
|
478 |
+
|
479 |
+
>>> from sympy import I, oo, erfi
|
480 |
+
>>> from sympy.abc import z
|
481 |
+
|
482 |
+
Several special values are known:
|
483 |
+
|
484 |
+
>>> erfi(0)
|
485 |
+
0
|
486 |
+
>>> erfi(oo)
|
487 |
+
oo
|
488 |
+
>>> erfi(-oo)
|
489 |
+
-oo
|
490 |
+
>>> erfi(I*oo)
|
491 |
+
I
|
492 |
+
>>> erfi(-I*oo)
|
493 |
+
-I
|
494 |
+
|
495 |
+
In general one can pull out factors of -1 and $I$ from the argument:
|
496 |
+
|
497 |
+
>>> erfi(-z)
|
498 |
+
-erfi(z)
|
499 |
+
|
500 |
+
>>> from sympy import conjugate
|
501 |
+
>>> conjugate(erfi(z))
|
502 |
+
erfi(conjugate(z))
|
503 |
+
|
504 |
+
Differentiation with respect to $z$ is supported:
|
505 |
+
|
506 |
+
>>> from sympy import diff
|
507 |
+
>>> diff(erfi(z), z)
|
508 |
+
2*exp(z**2)/sqrt(pi)
|
509 |
+
|
510 |
+
We can numerically evaluate the imaginary error function to arbitrary
|
511 |
+
precision on the whole complex plane:
|
512 |
+
|
513 |
+
>>> erfi(2).evalf(30)
|
514 |
+
18.5648024145755525987042919132
|
515 |
+
|
516 |
+
>>> erfi(-2*I).evalf(30)
|
517 |
+
-0.995322265018952734162069256367*I
|
518 |
+
|
519 |
+
See Also
|
520 |
+
========
|
521 |
+
|
522 |
+
erf: Gaussian error function.
|
523 |
+
erfc: Complementary error function.
|
524 |
+
erf2: Two-argument error function.
|
525 |
+
erfinv: Inverse error function.
|
526 |
+
erfcinv: Inverse Complementary error function.
|
527 |
+
erf2inv: Inverse two-argument error function.
|
528 |
+
|
529 |
+
References
|
530 |
+
==========
|
531 |
+
|
532 |
+
.. [1] https://en.wikipedia.org/wiki/Error_function
|
533 |
+
.. [2] https://mathworld.wolfram.com/Erfi.html
|
534 |
+
.. [3] https://functions.wolfram.com/GammaBetaErf/Erfi
|
535 |
+
|
536 |
+
"""
|
537 |
+
|
538 |
+
unbranched = True
|
539 |
+
|
540 |
+
def fdiff(self, argindex=1):
|
541 |
+
if argindex == 1:
|
542 |
+
return 2*exp(self.args[0]**2)/sqrt(pi)
|
543 |
+
else:
|
544 |
+
raise ArgumentIndexError(self, argindex)
|
545 |
+
|
546 |
+
@classmethod
|
547 |
+
def eval(cls, z):
|
548 |
+
if z.is_Number:
|
549 |
+
if z is S.NaN:
|
550 |
+
return S.NaN
|
551 |
+
elif z.is_zero:
|
552 |
+
return S.Zero
|
553 |
+
elif z is S.Infinity:
|
554 |
+
return S.Infinity
|
555 |
+
|
556 |
+
if z.is_zero:
|
557 |
+
return S.Zero
|
558 |
+
|
559 |
+
# Try to pull out factors of -1
|
560 |
+
if z.could_extract_minus_sign():
|
561 |
+
return -cls(-z)
|
562 |
+
|
563 |
+
# Try to pull out factors of I
|
564 |
+
nz = z.extract_multiplicatively(I)
|
565 |
+
if nz is not None:
|
566 |
+
if nz is S.Infinity:
|
567 |
+
return I
|
568 |
+
if isinstance(nz, erfinv):
|
569 |
+
return I*nz.args[0]
|
570 |
+
if isinstance(nz, erfcinv):
|
571 |
+
return I*(S.One - nz.args[0])
|
572 |
+
# Only happens with unevaluated erf2inv
|
573 |
+
if isinstance(nz, erf2inv) and nz.args[0].is_zero:
|
574 |
+
return I*nz.args[1]
|
575 |
+
|
576 |
+
@staticmethod
|
577 |
+
@cacheit
|
578 |
+
def taylor_term(n, x, *previous_terms):
|
579 |
+
if n < 0 or n % 2 == 0:
|
580 |
+
return S.Zero
|
581 |
+
else:
|
582 |
+
x = sympify(x)
|
583 |
+
k = floor((n - 1)/S(2))
|
584 |
+
if len(previous_terms) > 2:
|
585 |
+
return previous_terms[-2] * x**2 * (n - 2)/(n*k)
|
586 |
+
else:
|
587 |
+
return 2 * x**n/(n*factorial(k)*sqrt(pi))
|
588 |
+
|
589 |
+
def _eval_conjugate(self):
|
590 |
+
return self.func(self.args[0].conjugate())
|
591 |
+
|
592 |
+
def _eval_is_extended_real(self):
|
593 |
+
return self.args[0].is_extended_real
|
594 |
+
|
595 |
+
def _eval_is_zero(self):
|
596 |
+
return self.args[0].is_zero
|
597 |
+
|
598 |
+
def _eval_rewrite_as_tractable(self, z, limitvar=None, **kwargs):
|
599 |
+
return self.rewrite(erf).rewrite("tractable", deep=True, limitvar=limitvar)
|
600 |
+
|
601 |
+
def _eval_rewrite_as_erf(self, z, **kwargs):
|
602 |
+
return -I*erf(I*z)
|
603 |
+
|
604 |
+
def _eval_rewrite_as_erfc(self, z, **kwargs):
|
605 |
+
return I*erfc(I*z) - I
|
606 |
+
|
607 |
+
def _eval_rewrite_as_fresnels(self, z, **kwargs):
|
608 |
+
arg = (S.One + I)*z/sqrt(pi)
|
609 |
+
return (S.One - I)*(fresnelc(arg) - I*fresnels(arg))
|
610 |
+
|
611 |
+
def _eval_rewrite_as_fresnelc(self, z, **kwargs):
|
612 |
+
arg = (S.One + I)*z/sqrt(pi)
|
613 |
+
return (S.One - I)*(fresnelc(arg) - I*fresnels(arg))
|
614 |
+
|
615 |
+
def _eval_rewrite_as_meijerg(self, z, **kwargs):
|
616 |
+
return z/sqrt(pi)*meijerg([S.Half], [], [0], [Rational(-1, 2)], -z**2)
|
617 |
+
|
618 |
+
def _eval_rewrite_as_hyper(self, z, **kwargs):
|
619 |
+
return 2*z/sqrt(pi)*hyper([S.Half], [3*S.Half], z**2)
|
620 |
+
|
621 |
+
def _eval_rewrite_as_uppergamma(self, z, **kwargs):
|
622 |
+
from sympy.functions.special.gamma_functions import uppergamma
|
623 |
+
return sqrt(-z**2)/z*(uppergamma(S.Half, -z**2)/sqrt(pi) - S.One)
|
624 |
+
|
625 |
+
def _eval_rewrite_as_expint(self, z, **kwargs):
|
626 |
+
return sqrt(-z**2)/z - z*expint(S.Half, -z**2)/sqrt(pi)
|
627 |
+
|
628 |
+
def _eval_expand_func(self, **hints):
|
629 |
+
return self.rewrite(erf)
|
630 |
+
|
631 |
+
as_real_imag = real_to_real_as_real_imag
|
632 |
+
|
633 |
+
def _eval_as_leading_term(self, x, logx=None, cdir=0):
|
634 |
+
arg = self.args[0].as_leading_term(x, logx=logx, cdir=cdir)
|
635 |
+
arg0 = arg.subs(x, 0)
|
636 |
+
|
637 |
+
if x in arg.free_symbols and arg0.is_zero:
|
638 |
+
return 2*arg/sqrt(pi)
|
639 |
+
elif arg0.is_finite:
|
640 |
+
return self.func(arg0)
|
641 |
+
return self.func(arg)
|
642 |
+
|
643 |
+
def _eval_aseries(self, n, args0, x, logx):
|
644 |
+
from sympy.series.order import Order
|
645 |
+
point = args0[0]
|
646 |
+
|
647 |
+
if point is S.Infinity:
|
648 |
+
z = self.args[0]
|
649 |
+
s = [factorial2(2*k - 1) / (2**k * z**(2*k + 1))
|
650 |
+
for k in range(n)] + [Order(1/z**n, x)]
|
651 |
+
return -I + (exp(z**2)/sqrt(pi)) * Add(*s)
|
652 |
+
|
653 |
+
return super(erfi, self)._eval_aseries(n, args0, x, logx)
|
654 |
+
|
655 |
+
|
656 |
+
class erf2(Function):
|
657 |
+
r"""
|
658 |
+
Two-argument error function.
|
659 |
+
|
660 |
+
Explanation
|
661 |
+
===========
|
662 |
+
|
663 |
+
This function is defined as:
|
664 |
+
|
665 |
+
.. math ::
|
666 |
+
\mathrm{erf2}(x, y) = \frac{2}{\sqrt{\pi}} \int_x^y e^{-t^2} \mathrm{d}t
|
667 |
+
|
668 |
+
Examples
|
669 |
+
========
|
670 |
+
|
671 |
+
>>> from sympy import oo, erf2
|
672 |
+
>>> from sympy.abc import x, y
|
673 |
+
|
674 |
+
Several special values are known:
|
675 |
+
|
676 |
+
>>> erf2(0, 0)
|
677 |
+
0
|
678 |
+
>>> erf2(x, x)
|
679 |
+
0
|
680 |
+
>>> erf2(x, oo)
|
681 |
+
1 - erf(x)
|
682 |
+
>>> erf2(x, -oo)
|
683 |
+
-erf(x) - 1
|
684 |
+
>>> erf2(oo, y)
|
685 |
+
erf(y) - 1
|
686 |
+
>>> erf2(-oo, y)
|
687 |
+
erf(y) + 1
|
688 |
+
|
689 |
+
In general one can pull out factors of -1:
|
690 |
+
|
691 |
+
>>> erf2(-x, -y)
|
692 |
+
-erf2(x, y)
|
693 |
+
|
694 |
+
The error function obeys the mirror symmetry:
|
695 |
+
|
696 |
+
>>> from sympy import conjugate
|
697 |
+
>>> conjugate(erf2(x, y))
|
698 |
+
erf2(conjugate(x), conjugate(y))
|
699 |
+
|
700 |
+
Differentiation with respect to $x$, $y$ is supported:
|
701 |
+
|
702 |
+
>>> from sympy import diff
|
703 |
+
>>> diff(erf2(x, y), x)
|
704 |
+
-2*exp(-x**2)/sqrt(pi)
|
705 |
+
>>> diff(erf2(x, y), y)
|
706 |
+
2*exp(-y**2)/sqrt(pi)
|
707 |
+
|
708 |
+
See Also
|
709 |
+
========
|
710 |
+
|
711 |
+
erf: Gaussian error function.
|
712 |
+
erfc: Complementary error function.
|
713 |
+
erfi: Imaginary error function.
|
714 |
+
erfinv: Inverse error function.
|
715 |
+
erfcinv: Inverse Complementary error function.
|
716 |
+
erf2inv: Inverse two-argument error function.
|
717 |
+
|
718 |
+
References
|
719 |
+
==========
|
720 |
+
|
721 |
+
.. [1] https://functions.wolfram.com/GammaBetaErf/Erf2/
|
722 |
+
|
723 |
+
"""
|
724 |
+
|
725 |
+
|
726 |
+
def fdiff(self, argindex):
|
727 |
+
x, y = self.args
|
728 |
+
if argindex == 1:
|
729 |
+
return -2*exp(-x**2)/sqrt(pi)
|
730 |
+
elif argindex == 2:
|
731 |
+
return 2*exp(-y**2)/sqrt(pi)
|
732 |
+
else:
|
733 |
+
raise ArgumentIndexError(self, argindex)
|
734 |
+
|
735 |
+
@classmethod
|
736 |
+
def eval(cls, x, y):
|
737 |
+
chk = (S.Infinity, S.NegativeInfinity, S.Zero)
|
738 |
+
if x is S.NaN or y is S.NaN:
|
739 |
+
return S.NaN
|
740 |
+
elif x == y:
|
741 |
+
return S.Zero
|
742 |
+
elif x in chk or y in chk:
|
743 |
+
return erf(y) - erf(x)
|
744 |
+
|
745 |
+
if isinstance(y, erf2inv) and y.args[0] == x:
|
746 |
+
return y.args[1]
|
747 |
+
|
748 |
+
if x.is_zero or y.is_zero or x.is_extended_real and x.is_infinite or \
|
749 |
+
y.is_extended_real and y.is_infinite:
|
750 |
+
return erf(y) - erf(x)
|
751 |
+
|
752 |
+
#Try to pull out -1 factor
|
753 |
+
sign_x = x.could_extract_minus_sign()
|
754 |
+
sign_y = y.could_extract_minus_sign()
|
755 |
+
if (sign_x and sign_y):
|
756 |
+
return -cls(-x, -y)
|
757 |
+
elif (sign_x or sign_y):
|
758 |
+
return erf(y)-erf(x)
|
759 |
+
|
760 |
+
def _eval_conjugate(self):
|
761 |
+
return self.func(self.args[0].conjugate(), self.args[1].conjugate())
|
762 |
+
|
763 |
+
def _eval_is_extended_real(self):
|
764 |
+
return self.args[0].is_extended_real and self.args[1].is_extended_real
|
765 |
+
|
766 |
+
def _eval_rewrite_as_erf(self, x, y, **kwargs):
|
767 |
+
return erf(y) - erf(x)
|
768 |
+
|
769 |
+
def _eval_rewrite_as_erfc(self, x, y, **kwargs):
|
770 |
+
return erfc(x) - erfc(y)
|
771 |
+
|
772 |
+
def _eval_rewrite_as_erfi(self, x, y, **kwargs):
|
773 |
+
return I*(erfi(I*x)-erfi(I*y))
|
774 |
+
|
775 |
+
def _eval_rewrite_as_fresnels(self, x, y, **kwargs):
|
776 |
+
return erf(y).rewrite(fresnels) - erf(x).rewrite(fresnels)
|
777 |
+
|
778 |
+
def _eval_rewrite_as_fresnelc(self, x, y, **kwargs):
|
779 |
+
return erf(y).rewrite(fresnelc) - erf(x).rewrite(fresnelc)
|
780 |
+
|
781 |
+
def _eval_rewrite_as_meijerg(self, x, y, **kwargs):
|
782 |
+
return erf(y).rewrite(meijerg) - erf(x).rewrite(meijerg)
|
783 |
+
|
784 |
+
def _eval_rewrite_as_hyper(self, x, y, **kwargs):
|
785 |
+
return erf(y).rewrite(hyper) - erf(x).rewrite(hyper)
|
786 |
+
|
787 |
+
def _eval_rewrite_as_uppergamma(self, x, y, **kwargs):
|
788 |
+
from sympy.functions.special.gamma_functions import uppergamma
|
789 |
+
return (sqrt(y**2)/y*(S.One - uppergamma(S.Half, y**2)/sqrt(pi)) -
|
790 |
+
sqrt(x**2)/x*(S.One - uppergamma(S.Half, x**2)/sqrt(pi)))
|
791 |
+
|
792 |
+
def _eval_rewrite_as_expint(self, x, y, **kwargs):
|
793 |
+
return erf(y).rewrite(expint) - erf(x).rewrite(expint)
|
794 |
+
|
795 |
+
def _eval_expand_func(self, **hints):
|
796 |
+
return self.rewrite(erf)
|
797 |
+
|
798 |
+
def _eval_is_zero(self):
|
799 |
+
return is_eq(*self.args)
|
800 |
+
|
801 |
+
class erfinv(Function):
|
802 |
+
r"""
|
803 |
+
Inverse Error Function. The erfinv function is defined as:
|
804 |
+
|
805 |
+
.. math ::
|
806 |
+
\mathrm{erf}(x) = y \quad \Rightarrow \quad \mathrm{erfinv}(y) = x
|
807 |
+
|
808 |
+
Examples
|
809 |
+
========
|
810 |
+
|
811 |
+
>>> from sympy import erfinv
|
812 |
+
>>> from sympy.abc import x
|
813 |
+
|
814 |
+
Several special values are known:
|
815 |
+
|
816 |
+
>>> erfinv(0)
|
817 |
+
0
|
818 |
+
>>> erfinv(1)
|
819 |
+
oo
|
820 |
+
|
821 |
+
Differentiation with respect to $x$ is supported:
|
822 |
+
|
823 |
+
>>> from sympy import diff
|
824 |
+
>>> diff(erfinv(x), x)
|
825 |
+
sqrt(pi)*exp(erfinv(x)**2)/2
|
826 |
+
|
827 |
+
We can numerically evaluate the inverse error function to arbitrary
|
828 |
+
precision on [-1, 1]:
|
829 |
+
|
830 |
+
>>> erfinv(0.2).evalf(30)
|
831 |
+
0.179143454621291692285822705344
|
832 |
+
|
833 |
+
See Also
|
834 |
+
========
|
835 |
+
|
836 |
+
erf: Gaussian error function.
|
837 |
+
erfc: Complementary error function.
|
838 |
+
erfi: Imaginary error function.
|
839 |
+
erf2: Two-argument error function.
|
840 |
+
erfcinv: Inverse Complementary error function.
|
841 |
+
erf2inv: Inverse two-argument error function.
|
842 |
+
|
843 |
+
References
|
844 |
+
==========
|
845 |
+
|
846 |
+
.. [1] https://en.wikipedia.org/wiki/Error_function#Inverse_functions
|
847 |
+
.. [2] https://functions.wolfram.com/GammaBetaErf/InverseErf/
|
848 |
+
|
849 |
+
"""
|
850 |
+
|
851 |
+
|
852 |
+
def fdiff(self, argindex =1):
|
853 |
+
if argindex == 1:
|
854 |
+
return sqrt(pi)*exp(self.func(self.args[0])**2)*S.Half
|
855 |
+
else :
|
856 |
+
raise ArgumentIndexError(self, argindex)
|
857 |
+
|
858 |
+
def inverse(self, argindex=1):
|
859 |
+
"""
|
860 |
+
Returns the inverse of this function.
|
861 |
+
|
862 |
+
"""
|
863 |
+
return erf
|
864 |
+
|
865 |
+
@classmethod
|
866 |
+
def eval(cls, z):
|
867 |
+
if z is S.NaN:
|
868 |
+
return S.NaN
|
869 |
+
elif z is S.NegativeOne:
|
870 |
+
return S.NegativeInfinity
|
871 |
+
elif z.is_zero:
|
872 |
+
return S.Zero
|
873 |
+
elif z is S.One:
|
874 |
+
return S.Infinity
|
875 |
+
|
876 |
+
if isinstance(z, erf) and z.args[0].is_extended_real:
|
877 |
+
return z.args[0]
|
878 |
+
|
879 |
+
if z.is_zero:
|
880 |
+
return S.Zero
|
881 |
+
|
882 |
+
# Try to pull out factors of -1
|
883 |
+
nz = z.extract_multiplicatively(-1)
|
884 |
+
if nz is not None and (isinstance(nz, erf) and (nz.args[0]).is_extended_real):
|
885 |
+
return -nz.args[0]
|
886 |
+
|
887 |
+
def _eval_rewrite_as_erfcinv(self, z, **kwargs):
|
888 |
+
return erfcinv(1-z)
|
889 |
+
|
890 |
+
def _eval_is_zero(self):
|
891 |
+
return self.args[0].is_zero
|
892 |
+
|
893 |
+
|
894 |
+
class erfcinv (Function):
|
895 |
+
r"""
|
896 |
+
Inverse Complementary Error Function. The erfcinv function is defined as:
|
897 |
+
|
898 |
+
.. math ::
|
899 |
+
\mathrm{erfc}(x) = y \quad \Rightarrow \quad \mathrm{erfcinv}(y) = x
|
900 |
+
|
901 |
+
Examples
|
902 |
+
========
|
903 |
+
|
904 |
+
>>> from sympy import erfcinv
|
905 |
+
>>> from sympy.abc import x
|
906 |
+
|
907 |
+
Several special values are known:
|
908 |
+
|
909 |
+
>>> erfcinv(1)
|
910 |
+
0
|
911 |
+
>>> erfcinv(0)
|
912 |
+
oo
|
913 |
+
|
914 |
+
Differentiation with respect to $x$ is supported:
|
915 |
+
|
916 |
+
>>> from sympy import diff
|
917 |
+
>>> diff(erfcinv(x), x)
|
918 |
+
-sqrt(pi)*exp(erfcinv(x)**2)/2
|
919 |
+
|
920 |
+
See Also
|
921 |
+
========
|
922 |
+
|
923 |
+
erf: Gaussian error function.
|
924 |
+
erfc: Complementary error function.
|
925 |
+
erfi: Imaginary error function.
|
926 |
+
erf2: Two-argument error function.
|
927 |
+
erfinv: Inverse error function.
|
928 |
+
erf2inv: Inverse two-argument error function.
|
929 |
+
|
930 |
+
References
|
931 |
+
==========
|
932 |
+
|
933 |
+
.. [1] https://en.wikipedia.org/wiki/Error_function#Inverse_functions
|
934 |
+
.. [2] https://functions.wolfram.com/GammaBetaErf/InverseErfc/
|
935 |
+
|
936 |
+
"""
|
937 |
+
|
938 |
+
|
939 |
+
def fdiff(self, argindex =1):
|
940 |
+
if argindex == 1:
|
941 |
+
return -sqrt(pi)*exp(self.func(self.args[0])**2)*S.Half
|
942 |
+
else:
|
943 |
+
raise ArgumentIndexError(self, argindex)
|
944 |
+
|
945 |
+
def inverse(self, argindex=1):
|
946 |
+
"""
|
947 |
+
Returns the inverse of this function.
|
948 |
+
|
949 |
+
"""
|
950 |
+
return erfc
|
951 |
+
|
952 |
+
@classmethod
|
953 |
+
def eval(cls, z):
|
954 |
+
if z is S.NaN:
|
955 |
+
return S.NaN
|
956 |
+
elif z.is_zero:
|
957 |
+
return S.Infinity
|
958 |
+
elif z is S.One:
|
959 |
+
return S.Zero
|
960 |
+
elif z == 2:
|
961 |
+
return S.NegativeInfinity
|
962 |
+
|
963 |
+
if z.is_zero:
|
964 |
+
return S.Infinity
|
965 |
+
|
966 |
+
def _eval_rewrite_as_erfinv(self, z, **kwargs):
|
967 |
+
return erfinv(1-z)
|
968 |
+
|
969 |
+
def _eval_is_zero(self):
|
970 |
+
return (self.args[0] - 1).is_zero
|
971 |
+
|
972 |
+
def _eval_is_infinite(self):
|
973 |
+
return self.args[0].is_zero
|
974 |
+
|
975 |
+
|
976 |
+
class erf2inv(Function):
|
977 |
+
r"""
|
978 |
+
Two-argument Inverse error function. The erf2inv function is defined as:
|
979 |
+
|
980 |
+
.. math ::
|
981 |
+
\mathrm{erf2}(x, w) = y \quad \Rightarrow \quad \mathrm{erf2inv}(x, y) = w
|
982 |
+
|
983 |
+
Examples
|
984 |
+
========
|
985 |
+
|
986 |
+
>>> from sympy import erf2inv, oo
|
987 |
+
>>> from sympy.abc import x, y
|
988 |
+
|
989 |
+
Several special values are known:
|
990 |
+
|
991 |
+
>>> erf2inv(0, 0)
|
992 |
+
0
|
993 |
+
>>> erf2inv(1, 0)
|
994 |
+
1
|
995 |
+
>>> erf2inv(0, 1)
|
996 |
+
oo
|
997 |
+
>>> erf2inv(0, y)
|
998 |
+
erfinv(y)
|
999 |
+
>>> erf2inv(oo, y)
|
1000 |
+
erfcinv(-y)
|
1001 |
+
|
1002 |
+
Differentiation with respect to $x$ and $y$ is supported:
|
1003 |
+
|
1004 |
+
>>> from sympy import diff
|
1005 |
+
>>> diff(erf2inv(x, y), x)
|
1006 |
+
exp(-x**2 + erf2inv(x, y)**2)
|
1007 |
+
>>> diff(erf2inv(x, y), y)
|
1008 |
+
sqrt(pi)*exp(erf2inv(x, y)**2)/2
|
1009 |
+
|
1010 |
+
See Also
|
1011 |
+
========
|
1012 |
+
|
1013 |
+
erf: Gaussian error function.
|
1014 |
+
erfc: Complementary error function.
|
1015 |
+
erfi: Imaginary error function.
|
1016 |
+
erf2: Two-argument error function.
|
1017 |
+
erfinv: Inverse error function.
|
1018 |
+
erfcinv: Inverse complementary error function.
|
1019 |
+
|
1020 |
+
References
|
1021 |
+
==========
|
1022 |
+
|
1023 |
+
.. [1] https://functions.wolfram.com/GammaBetaErf/InverseErf2/
|
1024 |
+
|
1025 |
+
"""
|
1026 |
+
|
1027 |
+
|
1028 |
+
def fdiff(self, argindex):
|
1029 |
+
x, y = self.args
|
1030 |
+
if argindex == 1:
|
1031 |
+
return exp(self.func(x,y)**2-x**2)
|
1032 |
+
elif argindex == 2:
|
1033 |
+
return sqrt(pi)*S.Half*exp(self.func(x,y)**2)
|
1034 |
+
else:
|
1035 |
+
raise ArgumentIndexError(self, argindex)
|
1036 |
+
|
1037 |
+
@classmethod
|
1038 |
+
def eval(cls, x, y):
|
1039 |
+
if x is S.NaN or y is S.NaN:
|
1040 |
+
return S.NaN
|
1041 |
+
elif x.is_zero and y.is_zero:
|
1042 |
+
return S.Zero
|
1043 |
+
elif x.is_zero and y is S.One:
|
1044 |
+
return S.Infinity
|
1045 |
+
elif x is S.One and y.is_zero:
|
1046 |
+
return S.One
|
1047 |
+
elif x.is_zero:
|
1048 |
+
return erfinv(y)
|
1049 |
+
elif x is S.Infinity:
|
1050 |
+
return erfcinv(-y)
|
1051 |
+
elif y.is_zero:
|
1052 |
+
return x
|
1053 |
+
elif y is S.Infinity:
|
1054 |
+
return erfinv(x)
|
1055 |
+
|
1056 |
+
if x.is_zero:
|
1057 |
+
if y.is_zero:
|
1058 |
+
return S.Zero
|
1059 |
+
else:
|
1060 |
+
return erfinv(y)
|
1061 |
+
if y.is_zero:
|
1062 |
+
return x
|
1063 |
+
|
1064 |
+
def _eval_is_zero(self):
|
1065 |
+
x, y = self.args
|
1066 |
+
if x.is_zero and y.is_zero:
|
1067 |
+
return True
|
1068 |
+
|
1069 |
+
###############################################################################
|
1070 |
+
#################### EXPONENTIAL INTEGRALS ####################################
|
1071 |
+
###############################################################################
|
1072 |
+
|
1073 |
+
class Ei(Function):
|
1074 |
+
r"""
|
1075 |
+
The classical exponential integral.
|
1076 |
+
|
1077 |
+
Explanation
|
1078 |
+
===========
|
1079 |
+
|
1080 |
+
For use in SymPy, this function is defined as
|
1081 |
+
|
1082 |
+
.. math:: \operatorname{Ei}(x) = \sum_{n=1}^\infty \frac{x^n}{n\, n!}
|
1083 |
+
+ \log(x) + \gamma,
|
1084 |
+
|
1085 |
+
where $\gamma$ is the Euler-Mascheroni constant.
|
1086 |
+
|
1087 |
+
If $x$ is a polar number, this defines an analytic function on the
|
1088 |
+
Riemann surface of the logarithm. Otherwise this defines an analytic
|
1089 |
+
function in the cut plane $\mathbb{C} \setminus (-\infty, 0]$.
|
1090 |
+
|
1091 |
+
**Background**
|
1092 |
+
|
1093 |
+
The name exponential integral comes from the following statement:
|
1094 |
+
|
1095 |
+
.. math:: \operatorname{Ei}(x) = \int_{-\infty}^x \frac{e^t}{t} \mathrm{d}t
|
1096 |
+
|
1097 |
+
If the integral is interpreted as a Cauchy principal value, this statement
|
1098 |
+
holds for $x > 0$ and $\operatorname{Ei}(x)$ as defined above.
|
1099 |
+
|
1100 |
+
Examples
|
1101 |
+
========
|
1102 |
+
|
1103 |
+
>>> from sympy import Ei, polar_lift, exp_polar, I, pi
|
1104 |
+
>>> from sympy.abc import x
|
1105 |
+
|
1106 |
+
>>> Ei(-1)
|
1107 |
+
Ei(-1)
|
1108 |
+
|
1109 |
+
This yields a real value:
|
1110 |
+
|
1111 |
+
>>> Ei(-1).n(chop=True)
|
1112 |
+
-0.219383934395520
|
1113 |
+
|
1114 |
+
On the other hand the analytic continuation is not real:
|
1115 |
+
|
1116 |
+
>>> Ei(polar_lift(-1)).n(chop=True)
|
1117 |
+
-0.21938393439552 + 3.14159265358979*I
|
1118 |
+
|
1119 |
+
The exponential integral has a logarithmic branch point at the origin:
|
1120 |
+
|
1121 |
+
>>> Ei(x*exp_polar(2*I*pi))
|
1122 |
+
Ei(x) + 2*I*pi
|
1123 |
+
|
1124 |
+
Differentiation is supported:
|
1125 |
+
|
1126 |
+
>>> Ei(x).diff(x)
|
1127 |
+
exp(x)/x
|
1128 |
+
|
1129 |
+
The exponential integral is related to many other special functions.
|
1130 |
+
For example:
|
1131 |
+
|
1132 |
+
>>> from sympy import expint, Shi
|
1133 |
+
>>> Ei(x).rewrite(expint)
|
1134 |
+
-expint(1, x*exp_polar(I*pi)) - I*pi
|
1135 |
+
>>> Ei(x).rewrite(Shi)
|
1136 |
+
Chi(x) + Shi(x)
|
1137 |
+
|
1138 |
+
See Also
|
1139 |
+
========
|
1140 |
+
|
1141 |
+
expint: Generalised exponential integral.
|
1142 |
+
E1: Special case of the generalised exponential integral.
|
1143 |
+
li: Logarithmic integral.
|
1144 |
+
Li: Offset logarithmic integral.
|
1145 |
+
Si: Sine integral.
|
1146 |
+
Ci: Cosine integral.
|
1147 |
+
Shi: Hyperbolic sine integral.
|
1148 |
+
Chi: Hyperbolic cosine integral.
|
1149 |
+
uppergamma: Upper incomplete gamma function.
|
1150 |
+
|
1151 |
+
References
|
1152 |
+
==========
|
1153 |
+
|
1154 |
+
.. [1] https://dlmf.nist.gov/6.6
|
1155 |
+
.. [2] https://en.wikipedia.org/wiki/Exponential_integral
|
1156 |
+
.. [3] Abramowitz & Stegun, section 5: https://web.archive.org/web/20201128173312/http://people.math.sfu.ca/~cbm/aands/page_228.htm
|
1157 |
+
|
1158 |
+
"""
|
1159 |
+
|
1160 |
+
|
1161 |
+
@classmethod
|
1162 |
+
def eval(cls, z):
|
1163 |
+
if z.is_zero:
|
1164 |
+
return S.NegativeInfinity
|
1165 |
+
elif z is S.Infinity:
|
1166 |
+
return S.Infinity
|
1167 |
+
elif z is S.NegativeInfinity:
|
1168 |
+
return S.Zero
|
1169 |
+
|
1170 |
+
if z.is_zero:
|
1171 |
+
return S.NegativeInfinity
|
1172 |
+
|
1173 |
+
nz, n = z.extract_branch_factor()
|
1174 |
+
if n:
|
1175 |
+
return Ei(nz) + 2*I*pi*n
|
1176 |
+
|
1177 |
+
def fdiff(self, argindex=1):
|
1178 |
+
arg = unpolarify(self.args[0])
|
1179 |
+
if argindex == 1:
|
1180 |
+
return exp(arg)/arg
|
1181 |
+
else:
|
1182 |
+
raise ArgumentIndexError(self, argindex)
|
1183 |
+
|
1184 |
+
def _eval_evalf(self, prec):
|
1185 |
+
if (self.args[0]/polar_lift(-1)).is_positive:
|
1186 |
+
return Function._eval_evalf(self, prec) + (I*pi)._eval_evalf(prec)
|
1187 |
+
return Function._eval_evalf(self, prec)
|
1188 |
+
|
1189 |
+
def _eval_rewrite_as_uppergamma(self, z, **kwargs):
|
1190 |
+
from sympy.functions.special.gamma_functions import uppergamma
|
1191 |
+
# XXX this does not currently work usefully because uppergamma
|
1192 |
+
# immediately turns into expint
|
1193 |
+
return -uppergamma(0, polar_lift(-1)*z) - I*pi
|
1194 |
+
|
1195 |
+
def _eval_rewrite_as_expint(self, z, **kwargs):
|
1196 |
+
return -expint(1, polar_lift(-1)*z) - I*pi
|
1197 |
+
|
1198 |
+
def _eval_rewrite_as_li(self, z, **kwargs):
|
1199 |
+
if isinstance(z, log):
|
1200 |
+
return li(z.args[0])
|
1201 |
+
# TODO:
|
1202 |
+
# Actually it only holds that:
|
1203 |
+
# Ei(z) = li(exp(z))
|
1204 |
+
# for -pi < imag(z) <= pi
|
1205 |
+
return li(exp(z))
|
1206 |
+
|
1207 |
+
def _eval_rewrite_as_Si(self, z, **kwargs):
|
1208 |
+
if z.is_negative:
|
1209 |
+
return Shi(z) + Chi(z) - I*pi
|
1210 |
+
else:
|
1211 |
+
return Shi(z) + Chi(z)
|
1212 |
+
_eval_rewrite_as_Ci = _eval_rewrite_as_Si
|
1213 |
+
_eval_rewrite_as_Chi = _eval_rewrite_as_Si
|
1214 |
+
_eval_rewrite_as_Shi = _eval_rewrite_as_Si
|
1215 |
+
|
1216 |
+
def _eval_rewrite_as_tractable(self, z, limitvar=None, **kwargs):
|
1217 |
+
return exp(z) * _eis(z)
|
1218 |
+
|
1219 |
+
def _eval_as_leading_term(self, x, logx=None, cdir=0):
|
1220 |
+
from sympy import re
|
1221 |
+
x0 = self.args[0].limit(x, 0)
|
1222 |
+
arg = self.args[0].as_leading_term(x, cdir=cdir)
|
1223 |
+
cdir = arg.dir(x, cdir)
|
1224 |
+
if x0.is_zero:
|
1225 |
+
c, e = arg.as_coeff_exponent(x)
|
1226 |
+
logx = log(x) if logx is None else logx
|
1227 |
+
return log(c) + e*logx + EulerGamma - (
|
1228 |
+
I*pi if re(cdir).is_negative else S.Zero)
|
1229 |
+
return super()._eval_as_leading_term(x, logx=logx, cdir=cdir)
|
1230 |
+
|
1231 |
+
def _eval_nseries(self, x, n, logx, cdir=0):
|
1232 |
+
x0 = self.args[0].limit(x, 0)
|
1233 |
+
if x0.is_zero:
|
1234 |
+
f = self._eval_rewrite_as_Si(*self.args)
|
1235 |
+
return f._eval_nseries(x, n, logx)
|
1236 |
+
return super()._eval_nseries(x, n, logx)
|
1237 |
+
|
1238 |
+
def _eval_aseries(self, n, args0, x, logx):
|
1239 |
+
from sympy.series.order import Order
|
1240 |
+
point = args0[0]
|
1241 |
+
|
1242 |
+
if point is S.Infinity:
|
1243 |
+
z = self.args[0]
|
1244 |
+
s = [factorial(k) / (z)**k for k in range(n)] + \
|
1245 |
+
[Order(1/z**n, x)]
|
1246 |
+
return (exp(z)/z) * Add(*s)
|
1247 |
+
|
1248 |
+
return super(Ei, self)._eval_aseries(n, args0, x, logx)
|
1249 |
+
|
1250 |
+
|
1251 |
+
class expint(Function):
|
1252 |
+
r"""
|
1253 |
+
Generalized exponential integral.
|
1254 |
+
|
1255 |
+
Explanation
|
1256 |
+
===========
|
1257 |
+
|
1258 |
+
This function is defined as
|
1259 |
+
|
1260 |
+
.. math:: \operatorname{E}_\nu(z) = z^{\nu - 1} \Gamma(1 - \nu, z),
|
1261 |
+
|
1262 |
+
where $\Gamma(1 - \nu, z)$ is the upper incomplete gamma function
|
1263 |
+
(``uppergamma``).
|
1264 |
+
|
1265 |
+
Hence for $z$ with positive real part we have
|
1266 |
+
|
1267 |
+
.. math:: \operatorname{E}_\nu(z)
|
1268 |
+
= \int_1^\infty \frac{e^{-zt}}{t^\nu} \mathrm{d}t,
|
1269 |
+
|
1270 |
+
which explains the name.
|
1271 |
+
|
1272 |
+
The representation as an incomplete gamma function provides an analytic
|
1273 |
+
continuation for $\operatorname{E}_\nu(z)$. If $\nu$ is a
|
1274 |
+
non-positive integer, the exponential integral is thus an unbranched
|
1275 |
+
function of $z$, otherwise there is a branch point at the origin.
|
1276 |
+
Refer to the incomplete gamma function documentation for details of the
|
1277 |
+
branching behavior.
|
1278 |
+
|
1279 |
+
Examples
|
1280 |
+
========
|
1281 |
+
|
1282 |
+
>>> from sympy import expint, S
|
1283 |
+
>>> from sympy.abc import nu, z
|
1284 |
+
|
1285 |
+
Differentiation is supported. Differentiation with respect to $z$ further
|
1286 |
+
explains the name: for integral orders, the exponential integral is an
|
1287 |
+
iterated integral of the exponential function.
|
1288 |
+
|
1289 |
+
>>> expint(nu, z).diff(z)
|
1290 |
+
-expint(nu - 1, z)
|
1291 |
+
|
1292 |
+
Differentiation with respect to $\nu$ has no classical expression:
|
1293 |
+
|
1294 |
+
>>> expint(nu, z).diff(nu)
|
1295 |
+
-z**(nu - 1)*meijerg(((), (1, 1)), ((0, 0, 1 - nu), ()), z)
|
1296 |
+
|
1297 |
+
At non-postive integer orders, the exponential integral reduces to the
|
1298 |
+
exponential function:
|
1299 |
+
|
1300 |
+
>>> expint(0, z)
|
1301 |
+
exp(-z)/z
|
1302 |
+
>>> expint(-1, z)
|
1303 |
+
exp(-z)/z + exp(-z)/z**2
|
1304 |
+
|
1305 |
+
At half-integers it reduces to error functions:
|
1306 |
+
|
1307 |
+
>>> expint(S(1)/2, z)
|
1308 |
+
sqrt(pi)*erfc(sqrt(z))/sqrt(z)
|
1309 |
+
|
1310 |
+
At positive integer orders it can be rewritten in terms of exponentials
|
1311 |
+
and ``expint(1, z)``. Use ``expand_func()`` to do this:
|
1312 |
+
|
1313 |
+
>>> from sympy import expand_func
|
1314 |
+
>>> expand_func(expint(5, z))
|
1315 |
+
z**4*expint(1, z)/24 + (-z**3 + z**2 - 2*z + 6)*exp(-z)/24
|
1316 |
+
|
1317 |
+
The generalised exponential integral is essentially equivalent to the
|
1318 |
+
incomplete gamma function:
|
1319 |
+
|
1320 |
+
>>> from sympy import uppergamma
|
1321 |
+
>>> expint(nu, z).rewrite(uppergamma)
|
1322 |
+
z**(nu - 1)*uppergamma(1 - nu, z)
|
1323 |
+
|
1324 |
+
As such it is branched at the origin:
|
1325 |
+
|
1326 |
+
>>> from sympy import exp_polar, pi, I
|
1327 |
+
>>> expint(4, z*exp_polar(2*pi*I))
|
1328 |
+
I*pi*z**3/3 + expint(4, z)
|
1329 |
+
>>> expint(nu, z*exp_polar(2*pi*I))
|
1330 |
+
z**(nu - 1)*(exp(2*I*pi*nu) - 1)*gamma(1 - nu) + expint(nu, z)
|
1331 |
+
|
1332 |
+
See Also
|
1333 |
+
========
|
1334 |
+
|
1335 |
+
Ei: Another related function called exponential integral.
|
1336 |
+
E1: The classical case, returns expint(1, z).
|
1337 |
+
li: Logarithmic integral.
|
1338 |
+
Li: Offset logarithmic integral.
|
1339 |
+
Si: Sine integral.
|
1340 |
+
Ci: Cosine integral.
|
1341 |
+
Shi: Hyperbolic sine integral.
|
1342 |
+
Chi: Hyperbolic cosine integral.
|
1343 |
+
uppergamma
|
1344 |
+
|
1345 |
+
References
|
1346 |
+
==========
|
1347 |
+
|
1348 |
+
.. [1] https://dlmf.nist.gov/8.19
|
1349 |
+
.. [2] https://functions.wolfram.com/GammaBetaErf/ExpIntegralE/
|
1350 |
+
.. [3] https://en.wikipedia.org/wiki/Exponential_integral
|
1351 |
+
|
1352 |
+
"""
|
1353 |
+
|
1354 |
+
|
1355 |
+
@classmethod
|
1356 |
+
def eval(cls, nu, z):
|
1357 |
+
from sympy.functions.special.gamma_functions import (gamma, uppergamma)
|
1358 |
+
nu2 = unpolarify(nu)
|
1359 |
+
if nu != nu2:
|
1360 |
+
return expint(nu2, z)
|
1361 |
+
if nu.is_Integer and nu <= 0 or (not nu.is_Integer and (2*nu).is_Integer):
|
1362 |
+
return unpolarify(expand_mul(z**(nu - 1)*uppergamma(1 - nu, z)))
|
1363 |
+
|
1364 |
+
# Extract branching information. This can be deduced from what is
|
1365 |
+
# explained in lowergamma.eval().
|
1366 |
+
z, n = z.extract_branch_factor()
|
1367 |
+
if n is S.Zero:
|
1368 |
+
return
|
1369 |
+
if nu.is_integer:
|
1370 |
+
if not nu > 0:
|
1371 |
+
return
|
1372 |
+
return expint(nu, z) \
|
1373 |
+
- 2*pi*I*n*S.NegativeOne**(nu - 1)/factorial(nu - 1)*unpolarify(z)**(nu - 1)
|
1374 |
+
else:
|
1375 |
+
return (exp(2*I*pi*nu*n) - 1)*z**(nu - 1)*gamma(1 - nu) + expint(nu, z)
|
1376 |
+
|
1377 |
+
def fdiff(self, argindex):
|
1378 |
+
nu, z = self.args
|
1379 |
+
if argindex == 1:
|
1380 |
+
return -z**(nu - 1)*meijerg([], [1, 1], [0, 0, 1 - nu], [], z)
|
1381 |
+
elif argindex == 2:
|
1382 |
+
return -expint(nu - 1, z)
|
1383 |
+
else:
|
1384 |
+
raise ArgumentIndexError(self, argindex)
|
1385 |
+
|
1386 |
+
def _eval_rewrite_as_uppergamma(self, nu, z, **kwargs):
|
1387 |
+
from sympy.functions.special.gamma_functions import uppergamma
|
1388 |
+
return z**(nu - 1)*uppergamma(1 - nu, z)
|
1389 |
+
|
1390 |
+
def _eval_rewrite_as_Ei(self, nu, z, **kwargs):
|
1391 |
+
if nu == 1:
|
1392 |
+
return -Ei(z*exp_polar(-I*pi)) - I*pi
|
1393 |
+
elif nu.is_Integer and nu > 1:
|
1394 |
+
# DLMF, 8.19.7
|
1395 |
+
x = -unpolarify(z)
|
1396 |
+
return x**(nu - 1)/factorial(nu - 1)*E1(z).rewrite(Ei) + \
|
1397 |
+
exp(x)/factorial(nu - 1) * \
|
1398 |
+
Add(*[factorial(nu - k - 2)*x**k for k in range(nu - 1)])
|
1399 |
+
else:
|
1400 |
+
return self
|
1401 |
+
|
1402 |
+
def _eval_expand_func(self, **hints):
|
1403 |
+
return self.rewrite(Ei).rewrite(expint, **hints)
|
1404 |
+
|
1405 |
+
def _eval_rewrite_as_Si(self, nu, z, **kwargs):
|
1406 |
+
if nu != 1:
|
1407 |
+
return self
|
1408 |
+
return Shi(z) - Chi(z)
|
1409 |
+
_eval_rewrite_as_Ci = _eval_rewrite_as_Si
|
1410 |
+
_eval_rewrite_as_Chi = _eval_rewrite_as_Si
|
1411 |
+
_eval_rewrite_as_Shi = _eval_rewrite_as_Si
|
1412 |
+
|
1413 |
+
def _eval_nseries(self, x, n, logx, cdir=0):
|
1414 |
+
if not self.args[0].has(x):
|
1415 |
+
nu = self.args[0]
|
1416 |
+
if nu == 1:
|
1417 |
+
f = self._eval_rewrite_as_Si(*self.args)
|
1418 |
+
return f._eval_nseries(x, n, logx)
|
1419 |
+
elif nu.is_Integer and nu > 1:
|
1420 |
+
f = self._eval_rewrite_as_Ei(*self.args)
|
1421 |
+
return f._eval_nseries(x, n, logx)
|
1422 |
+
return super()._eval_nseries(x, n, logx)
|
1423 |
+
|
1424 |
+
def _eval_aseries(self, n, args0, x, logx):
|
1425 |
+
from sympy.series.order import Order
|
1426 |
+
point = args0[1]
|
1427 |
+
nu = self.args[0]
|
1428 |
+
|
1429 |
+
if point is S.Infinity:
|
1430 |
+
z = self.args[1]
|
1431 |
+
s = [S.NegativeOne**k * RisingFactorial(nu, k) / z**k for k in range(n)] + [Order(1/z**n, x)]
|
1432 |
+
return (exp(-z)/z) * Add(*s)
|
1433 |
+
|
1434 |
+
return super(expint, self)._eval_aseries(n, args0, x, logx)
|
1435 |
+
|
1436 |
+
|
1437 |
+
def E1(z):
|
1438 |
+
"""
|
1439 |
+
Classical case of the generalized exponential integral.
|
1440 |
+
|
1441 |
+
Explanation
|
1442 |
+
===========
|
1443 |
+
|
1444 |
+
This is equivalent to ``expint(1, z)``.
|
1445 |
+
|
1446 |
+
Examples
|
1447 |
+
========
|
1448 |
+
|
1449 |
+
>>> from sympy import E1
|
1450 |
+
>>> E1(0)
|
1451 |
+
expint(1, 0)
|
1452 |
+
|
1453 |
+
>>> E1(5)
|
1454 |
+
expint(1, 5)
|
1455 |
+
|
1456 |
+
See Also
|
1457 |
+
========
|
1458 |
+
|
1459 |
+
Ei: Exponential integral.
|
1460 |
+
expint: Generalised exponential integral.
|
1461 |
+
li: Logarithmic integral.
|
1462 |
+
Li: Offset logarithmic integral.
|
1463 |
+
Si: Sine integral.
|
1464 |
+
Ci: Cosine integral.
|
1465 |
+
Shi: Hyperbolic sine integral.
|
1466 |
+
Chi: Hyperbolic cosine integral.
|
1467 |
+
|
1468 |
+
"""
|
1469 |
+
return expint(1, z)
|
1470 |
+
|
1471 |
+
|
1472 |
+
class li(Function):
|
1473 |
+
r"""
|
1474 |
+
The classical logarithmic integral.
|
1475 |
+
|
1476 |
+
Explanation
|
1477 |
+
===========
|
1478 |
+
|
1479 |
+
For use in SymPy, this function is defined as
|
1480 |
+
|
1481 |
+
.. math:: \operatorname{li}(x) = \int_0^x \frac{1}{\log(t)} \mathrm{d}t \,.
|
1482 |
+
|
1483 |
+
Examples
|
1484 |
+
========
|
1485 |
+
|
1486 |
+
>>> from sympy import I, oo, li
|
1487 |
+
>>> from sympy.abc import z
|
1488 |
+
|
1489 |
+
Several special values are known:
|
1490 |
+
|
1491 |
+
>>> li(0)
|
1492 |
+
0
|
1493 |
+
>>> li(1)
|
1494 |
+
-oo
|
1495 |
+
>>> li(oo)
|
1496 |
+
oo
|
1497 |
+
|
1498 |
+
Differentiation with respect to $z$ is supported:
|
1499 |
+
|
1500 |
+
>>> from sympy import diff
|
1501 |
+
>>> diff(li(z), z)
|
1502 |
+
1/log(z)
|
1503 |
+
|
1504 |
+
Defining the ``li`` function via an integral:
|
1505 |
+
>>> from sympy import integrate
|
1506 |
+
>>> integrate(li(z))
|
1507 |
+
z*li(z) - Ei(2*log(z))
|
1508 |
+
|
1509 |
+
>>> integrate(li(z),z)
|
1510 |
+
z*li(z) - Ei(2*log(z))
|
1511 |
+
|
1512 |
+
|
1513 |
+
The logarithmic integral can also be defined in terms of ``Ei``:
|
1514 |
+
|
1515 |
+
>>> from sympy import Ei
|
1516 |
+
>>> li(z).rewrite(Ei)
|
1517 |
+
Ei(log(z))
|
1518 |
+
>>> diff(li(z).rewrite(Ei), z)
|
1519 |
+
1/log(z)
|
1520 |
+
|
1521 |
+
We can numerically evaluate the logarithmic integral to arbitrary precision
|
1522 |
+
on the whole complex plane (except the singular points):
|
1523 |
+
|
1524 |
+
>>> li(2).evalf(30)
|
1525 |
+
1.04516378011749278484458888919
|
1526 |
+
|
1527 |
+
>>> li(2*I).evalf(30)
|
1528 |
+
1.0652795784357498247001125598 + 3.08346052231061726610939702133*I
|
1529 |
+
|
1530 |
+
We can even compute Soldner's constant by the help of mpmath:
|
1531 |
+
|
1532 |
+
>>> from mpmath import findroot
|
1533 |
+
>>> findroot(li, 2)
|
1534 |
+
1.45136923488338
|
1535 |
+
|
1536 |
+
Further transformations include rewriting ``li`` in terms of
|
1537 |
+
the trigonometric integrals ``Si``, ``Ci``, ``Shi`` and ``Chi``:
|
1538 |
+
|
1539 |
+
>>> from sympy import Si, Ci, Shi, Chi
|
1540 |
+
>>> li(z).rewrite(Si)
|
1541 |
+
-log(I*log(z)) - log(1/log(z))/2 + log(log(z))/2 + Ci(I*log(z)) + Shi(log(z))
|
1542 |
+
>>> li(z).rewrite(Ci)
|
1543 |
+
-log(I*log(z)) - log(1/log(z))/2 + log(log(z))/2 + Ci(I*log(z)) + Shi(log(z))
|
1544 |
+
>>> li(z).rewrite(Shi)
|
1545 |
+
-log(1/log(z))/2 + log(log(z))/2 + Chi(log(z)) - Shi(log(z))
|
1546 |
+
>>> li(z).rewrite(Chi)
|
1547 |
+
-log(1/log(z))/2 + log(log(z))/2 + Chi(log(z)) - Shi(log(z))
|
1548 |
+
|
1549 |
+
See Also
|
1550 |
+
========
|
1551 |
+
|
1552 |
+
Li: Offset logarithmic integral.
|
1553 |
+
Ei: Exponential integral.
|
1554 |
+
expint: Generalised exponential integral.
|
1555 |
+
E1: Special case of the generalised exponential integral.
|
1556 |
+
Si: Sine integral.
|
1557 |
+
Ci: Cosine integral.
|
1558 |
+
Shi: Hyperbolic sine integral.
|
1559 |
+
Chi: Hyperbolic cosine integral.
|
1560 |
+
|
1561 |
+
References
|
1562 |
+
==========
|
1563 |
+
|
1564 |
+
.. [1] https://en.wikipedia.org/wiki/Logarithmic_integral
|
1565 |
+
.. [2] https://mathworld.wolfram.com/LogarithmicIntegral.html
|
1566 |
+
.. [3] https://dlmf.nist.gov/6
|
1567 |
+
.. [4] https://mathworld.wolfram.com/SoldnersConstant.html
|
1568 |
+
|
1569 |
+
"""
|
1570 |
+
|
1571 |
+
|
1572 |
+
@classmethod
|
1573 |
+
def eval(cls, z):
|
1574 |
+
if z.is_zero:
|
1575 |
+
return S.Zero
|
1576 |
+
elif z is S.One:
|
1577 |
+
return S.NegativeInfinity
|
1578 |
+
elif z is S.Infinity:
|
1579 |
+
return S.Infinity
|
1580 |
+
if z.is_zero:
|
1581 |
+
return S.Zero
|
1582 |
+
|
1583 |
+
def fdiff(self, argindex=1):
|
1584 |
+
arg = self.args[0]
|
1585 |
+
if argindex == 1:
|
1586 |
+
return S.One / log(arg)
|
1587 |
+
else:
|
1588 |
+
raise ArgumentIndexError(self, argindex)
|
1589 |
+
|
1590 |
+
def _eval_conjugate(self):
|
1591 |
+
z = self.args[0]
|
1592 |
+
# Exclude values on the branch cut (-oo, 0)
|
1593 |
+
if not z.is_extended_negative:
|
1594 |
+
return self.func(z.conjugate())
|
1595 |
+
|
1596 |
+
def _eval_rewrite_as_Li(self, z, **kwargs):
|
1597 |
+
return Li(z) + li(2)
|
1598 |
+
|
1599 |
+
def _eval_rewrite_as_Ei(self, z, **kwargs):
|
1600 |
+
return Ei(log(z))
|
1601 |
+
|
1602 |
+
def _eval_rewrite_as_uppergamma(self, z, **kwargs):
|
1603 |
+
from sympy.functions.special.gamma_functions import uppergamma
|
1604 |
+
return (-uppergamma(0, -log(z)) +
|
1605 |
+
S.Half*(log(log(z)) - log(S.One/log(z))) - log(-log(z)))
|
1606 |
+
|
1607 |
+
def _eval_rewrite_as_Si(self, z, **kwargs):
|
1608 |
+
return (Ci(I*log(z)) - I*Si(I*log(z)) -
|
1609 |
+
S.Half*(log(S.One/log(z)) - log(log(z))) - log(I*log(z)))
|
1610 |
+
|
1611 |
+
_eval_rewrite_as_Ci = _eval_rewrite_as_Si
|
1612 |
+
|
1613 |
+
def _eval_rewrite_as_Shi(self, z, **kwargs):
|
1614 |
+
return (Chi(log(z)) - Shi(log(z)) - S.Half*(log(S.One/log(z)) - log(log(z))))
|
1615 |
+
|
1616 |
+
_eval_rewrite_as_Chi = _eval_rewrite_as_Shi
|
1617 |
+
|
1618 |
+
def _eval_rewrite_as_hyper(self, z, **kwargs):
|
1619 |
+
return (log(z)*hyper((1, 1), (2, 2), log(z)) +
|
1620 |
+
S.Half*(log(log(z)) - log(S.One/log(z))) + EulerGamma)
|
1621 |
+
|
1622 |
+
def _eval_rewrite_as_meijerg(self, z, **kwargs):
|
1623 |
+
return (-log(-log(z)) - S.Half*(log(S.One/log(z)) - log(log(z)))
|
1624 |
+
- meijerg(((), (1,)), ((0, 0), ()), -log(z)))
|
1625 |
+
|
1626 |
+
def _eval_rewrite_as_tractable(self, z, limitvar=None, **kwargs):
|
1627 |
+
return z * _eis(log(z))
|
1628 |
+
|
1629 |
+
def _eval_nseries(self, x, n, logx, cdir=0):
|
1630 |
+
z = self.args[0]
|
1631 |
+
s = [(log(z))**k / (factorial(k) * k) for k in range(1, n)]
|
1632 |
+
return EulerGamma + log(log(z)) + Add(*s)
|
1633 |
+
|
1634 |
+
def _eval_is_zero(self):
|
1635 |
+
z = self.args[0]
|
1636 |
+
if z.is_zero:
|
1637 |
+
return True
|
1638 |
+
|
1639 |
+
class Li(Function):
|
1640 |
+
r"""
|
1641 |
+
The offset logarithmic integral.
|
1642 |
+
|
1643 |
+
Explanation
|
1644 |
+
===========
|
1645 |
+
|
1646 |
+
For use in SymPy, this function is defined as
|
1647 |
+
|
1648 |
+
.. math:: \operatorname{Li}(x) = \operatorname{li}(x) - \operatorname{li}(2)
|
1649 |
+
|
1650 |
+
Examples
|
1651 |
+
========
|
1652 |
+
|
1653 |
+
>>> from sympy import Li
|
1654 |
+
>>> from sympy.abc import z
|
1655 |
+
|
1656 |
+
The following special value is known:
|
1657 |
+
|
1658 |
+
>>> Li(2)
|
1659 |
+
0
|
1660 |
+
|
1661 |
+
Differentiation with respect to $z$ is supported:
|
1662 |
+
|
1663 |
+
>>> from sympy import diff
|
1664 |
+
>>> diff(Li(z), z)
|
1665 |
+
1/log(z)
|
1666 |
+
|
1667 |
+
The shifted logarithmic integral can be written in terms of $li(z)$:
|
1668 |
+
|
1669 |
+
>>> from sympy import li
|
1670 |
+
>>> Li(z).rewrite(li)
|
1671 |
+
li(z) - li(2)
|
1672 |
+
|
1673 |
+
We can numerically evaluate the logarithmic integral to arbitrary precision
|
1674 |
+
on the whole complex plane (except the singular points):
|
1675 |
+
|
1676 |
+
>>> Li(2).evalf(30)
|
1677 |
+
0
|
1678 |
+
|
1679 |
+
>>> Li(4).evalf(30)
|
1680 |
+
1.92242131492155809316615998938
|
1681 |
+
|
1682 |
+
See Also
|
1683 |
+
========
|
1684 |
+
|
1685 |
+
li: Logarithmic integral.
|
1686 |
+
Ei: Exponential integral.
|
1687 |
+
expint: Generalised exponential integral.
|
1688 |
+
E1: Special case of the generalised exponential integral.
|
1689 |
+
Si: Sine integral.
|
1690 |
+
Ci: Cosine integral.
|
1691 |
+
Shi: Hyperbolic sine integral.
|
1692 |
+
Chi: Hyperbolic cosine integral.
|
1693 |
+
|
1694 |
+
References
|
1695 |
+
==========
|
1696 |
+
|
1697 |
+
.. [1] https://en.wikipedia.org/wiki/Logarithmic_integral
|
1698 |
+
.. [2] https://mathworld.wolfram.com/LogarithmicIntegral.html
|
1699 |
+
.. [3] https://dlmf.nist.gov/6
|
1700 |
+
|
1701 |
+
"""
|
1702 |
+
|
1703 |
+
|
1704 |
+
@classmethod
|
1705 |
+
def eval(cls, z):
|
1706 |
+
if z is S.Infinity:
|
1707 |
+
return S.Infinity
|
1708 |
+
elif z == S(2):
|
1709 |
+
return S.Zero
|
1710 |
+
|
1711 |
+
def fdiff(self, argindex=1):
|
1712 |
+
arg = self.args[0]
|
1713 |
+
if argindex == 1:
|
1714 |
+
return S.One / log(arg)
|
1715 |
+
else:
|
1716 |
+
raise ArgumentIndexError(self, argindex)
|
1717 |
+
|
1718 |
+
def _eval_evalf(self, prec):
|
1719 |
+
return self.rewrite(li).evalf(prec)
|
1720 |
+
|
1721 |
+
def _eval_rewrite_as_li(self, z, **kwargs):
|
1722 |
+
return li(z) - li(2)
|
1723 |
+
|
1724 |
+
def _eval_rewrite_as_tractable(self, z, limitvar=None, **kwargs):
|
1725 |
+
return self.rewrite(li).rewrite("tractable", deep=True)
|
1726 |
+
|
1727 |
+
def _eval_nseries(self, x, n, logx, cdir=0):
|
1728 |
+
f = self._eval_rewrite_as_li(*self.args)
|
1729 |
+
return f._eval_nseries(x, n, logx)
|
1730 |
+
|
1731 |
+
###############################################################################
|
1732 |
+
#################### TRIGONOMETRIC INTEGRALS ##################################
|
1733 |
+
###############################################################################
|
1734 |
+
|
1735 |
+
class TrigonometricIntegral(Function):
|
1736 |
+
""" Base class for trigonometric integrals. """
|
1737 |
+
|
1738 |
+
|
1739 |
+
@classmethod
|
1740 |
+
def eval(cls, z):
|
1741 |
+
if z is S.Zero:
|
1742 |
+
return cls._atzero
|
1743 |
+
elif z is S.Infinity:
|
1744 |
+
return cls._atinf()
|
1745 |
+
elif z is S.NegativeInfinity:
|
1746 |
+
return cls._atneginf()
|
1747 |
+
|
1748 |
+
if z.is_zero:
|
1749 |
+
return cls._atzero
|
1750 |
+
|
1751 |
+
nz = z.extract_multiplicatively(polar_lift(I))
|
1752 |
+
if nz is None and cls._trigfunc(0) == 0:
|
1753 |
+
nz = z.extract_multiplicatively(I)
|
1754 |
+
if nz is not None:
|
1755 |
+
return cls._Ifactor(nz, 1)
|
1756 |
+
nz = z.extract_multiplicatively(polar_lift(-I))
|
1757 |
+
if nz is not None:
|
1758 |
+
return cls._Ifactor(nz, -1)
|
1759 |
+
|
1760 |
+
nz = z.extract_multiplicatively(polar_lift(-1))
|
1761 |
+
if nz is None and cls._trigfunc(0) == 0:
|
1762 |
+
nz = z.extract_multiplicatively(-1)
|
1763 |
+
if nz is not None:
|
1764 |
+
return cls._minusfactor(nz)
|
1765 |
+
|
1766 |
+
nz, n = z.extract_branch_factor()
|
1767 |
+
if n == 0 and nz == z:
|
1768 |
+
return
|
1769 |
+
return 2*pi*I*n*cls._trigfunc(0) + cls(nz)
|
1770 |
+
|
1771 |
+
def fdiff(self, argindex=1):
|
1772 |
+
arg = unpolarify(self.args[0])
|
1773 |
+
if argindex == 1:
|
1774 |
+
return self._trigfunc(arg)/arg
|
1775 |
+
else:
|
1776 |
+
raise ArgumentIndexError(self, argindex)
|
1777 |
+
|
1778 |
+
def _eval_rewrite_as_Ei(self, z, **kwargs):
|
1779 |
+
return self._eval_rewrite_as_expint(z).rewrite(Ei)
|
1780 |
+
|
1781 |
+
def _eval_rewrite_as_uppergamma(self, z, **kwargs):
|
1782 |
+
from sympy.functions.special.gamma_functions import uppergamma
|
1783 |
+
return self._eval_rewrite_as_expint(z).rewrite(uppergamma)
|
1784 |
+
|
1785 |
+
def _eval_nseries(self, x, n, logx, cdir=0):
|
1786 |
+
# NOTE this is fairly inefficient
|
1787 |
+
n += 1
|
1788 |
+
if self.args[0].subs(x, 0) != 0:
|
1789 |
+
return super()._eval_nseries(x, n, logx)
|
1790 |
+
baseseries = self._trigfunc(x)._eval_nseries(x, n, logx)
|
1791 |
+
if self._trigfunc(0) != 0:
|
1792 |
+
baseseries -= 1
|
1793 |
+
baseseries = baseseries.replace(Pow, lambda t, n: t**n/n, simultaneous=False)
|
1794 |
+
if self._trigfunc(0) != 0:
|
1795 |
+
baseseries += EulerGamma + log(x)
|
1796 |
+
return baseseries.subs(x, self.args[0])._eval_nseries(x, n, logx)
|
1797 |
+
|
1798 |
+
|
1799 |
+
class Si(TrigonometricIntegral):
|
1800 |
+
r"""
|
1801 |
+
Sine integral.
|
1802 |
+
|
1803 |
+
Explanation
|
1804 |
+
===========
|
1805 |
+
|
1806 |
+
This function is defined by
|
1807 |
+
|
1808 |
+
.. math:: \operatorname{Si}(z) = \int_0^z \frac{\sin{t}}{t} \mathrm{d}t.
|
1809 |
+
|
1810 |
+
It is an entire function.
|
1811 |
+
|
1812 |
+
Examples
|
1813 |
+
========
|
1814 |
+
|
1815 |
+
>>> from sympy import Si
|
1816 |
+
>>> from sympy.abc import z
|
1817 |
+
|
1818 |
+
The sine integral is an antiderivative of $sin(z)/z$:
|
1819 |
+
|
1820 |
+
>>> Si(z).diff(z)
|
1821 |
+
sin(z)/z
|
1822 |
+
|
1823 |
+
It is unbranched:
|
1824 |
+
|
1825 |
+
>>> from sympy import exp_polar, I, pi
|
1826 |
+
>>> Si(z*exp_polar(2*I*pi))
|
1827 |
+
Si(z)
|
1828 |
+
|
1829 |
+
Sine integral behaves much like ordinary sine under multiplication by ``I``:
|
1830 |
+
|
1831 |
+
>>> Si(I*z)
|
1832 |
+
I*Shi(z)
|
1833 |
+
>>> Si(-z)
|
1834 |
+
-Si(z)
|
1835 |
+
|
1836 |
+
It can also be expressed in terms of exponential integrals, but beware
|
1837 |
+
that the latter is branched:
|
1838 |
+
|
1839 |
+
>>> from sympy import expint
|
1840 |
+
>>> Si(z).rewrite(expint)
|
1841 |
+
-I*(-expint(1, z*exp_polar(-I*pi/2))/2 +
|
1842 |
+
expint(1, z*exp_polar(I*pi/2))/2) + pi/2
|
1843 |
+
|
1844 |
+
It can be rewritten in the form of sinc function (by definition):
|
1845 |
+
|
1846 |
+
>>> from sympy import sinc
|
1847 |
+
>>> Si(z).rewrite(sinc)
|
1848 |
+
Integral(sinc(t), (t, 0, z))
|
1849 |
+
|
1850 |
+
See Also
|
1851 |
+
========
|
1852 |
+
|
1853 |
+
Ci: Cosine integral.
|
1854 |
+
Shi: Hyperbolic sine integral.
|
1855 |
+
Chi: Hyperbolic cosine integral.
|
1856 |
+
Ei: Exponential integral.
|
1857 |
+
expint: Generalised exponential integral.
|
1858 |
+
sinc: unnormalized sinc function
|
1859 |
+
E1: Special case of the generalised exponential integral.
|
1860 |
+
li: Logarithmic integral.
|
1861 |
+
Li: Offset logarithmic integral.
|
1862 |
+
|
1863 |
+
References
|
1864 |
+
==========
|
1865 |
+
|
1866 |
+
.. [1] https://en.wikipedia.org/wiki/Trigonometric_integral
|
1867 |
+
|
1868 |
+
"""
|
1869 |
+
|
1870 |
+
_trigfunc = sin
|
1871 |
+
_atzero = S.Zero
|
1872 |
+
|
1873 |
+
@classmethod
|
1874 |
+
def _atinf(cls):
|
1875 |
+
return pi*S.Half
|
1876 |
+
|
1877 |
+
@classmethod
|
1878 |
+
def _atneginf(cls):
|
1879 |
+
return -pi*S.Half
|
1880 |
+
|
1881 |
+
@classmethod
|
1882 |
+
def _minusfactor(cls, z):
|
1883 |
+
return -Si(z)
|
1884 |
+
|
1885 |
+
@classmethod
|
1886 |
+
def _Ifactor(cls, z, sign):
|
1887 |
+
return I*Shi(z)*sign
|
1888 |
+
|
1889 |
+
def _eval_rewrite_as_expint(self, z, **kwargs):
|
1890 |
+
# XXX should we polarify z?
|
1891 |
+
return pi/2 + (E1(polar_lift(I)*z) - E1(polar_lift(-I)*z))/2/I
|
1892 |
+
|
1893 |
+
def _eval_rewrite_as_sinc(self, z, **kwargs):
|
1894 |
+
from sympy.integrals.integrals import Integral
|
1895 |
+
t = Symbol('t', Dummy=True)
|
1896 |
+
return Integral(sinc(t), (t, 0, z))
|
1897 |
+
|
1898 |
+
def _eval_aseries(self, n, args0, x, logx):
|
1899 |
+
from sympy.series.order import Order
|
1900 |
+
point = args0[0]
|
1901 |
+
|
1902 |
+
# Expansion at oo
|
1903 |
+
if point is S.Infinity:
|
1904 |
+
z = self.args[0]
|
1905 |
+
p = [S.NegativeOne**k * factorial(2*k) / z**(2*k)
|
1906 |
+
for k in range(int((n - 1)/2))] + [Order(1/z**n, x)]
|
1907 |
+
q = [S.NegativeOne**k * factorial(2*k + 1) / z**(2*k + 1)
|
1908 |
+
for k in range(int(n/2) - 1)] + [Order(1/z**n, x)]
|
1909 |
+
return pi/2 - (cos(z)/z)*Add(*p) - (sin(z)/z)*Add(*q)
|
1910 |
+
|
1911 |
+
# All other points are not handled
|
1912 |
+
return super(Si, self)._eval_aseries(n, args0, x, logx)
|
1913 |
+
|
1914 |
+
def _eval_is_zero(self):
|
1915 |
+
z = self.args[0]
|
1916 |
+
if z.is_zero:
|
1917 |
+
return True
|
1918 |
+
|
1919 |
+
|
1920 |
+
class Ci(TrigonometricIntegral):
|
1921 |
+
r"""
|
1922 |
+
Cosine integral.
|
1923 |
+
|
1924 |
+
Explanation
|
1925 |
+
===========
|
1926 |
+
|
1927 |
+
This function is defined for positive $x$ by
|
1928 |
+
|
1929 |
+
.. math:: \operatorname{Ci}(x) = \gamma + \log{x}
|
1930 |
+
+ \int_0^x \frac{\cos{t} - 1}{t} \mathrm{d}t
|
1931 |
+
= -\int_x^\infty \frac{\cos{t}}{t} \mathrm{d}t,
|
1932 |
+
|
1933 |
+
where $\gamma$ is the Euler-Mascheroni constant.
|
1934 |
+
|
1935 |
+
We have
|
1936 |
+
|
1937 |
+
.. math:: \operatorname{Ci}(z) =
|
1938 |
+
-\frac{\operatorname{E}_1\left(e^{i\pi/2} z\right)
|
1939 |
+
+ \operatorname{E}_1\left(e^{-i \pi/2} z\right)}{2}
|
1940 |
+
|
1941 |
+
which holds for all polar $z$ and thus provides an analytic
|
1942 |
+
continuation to the Riemann surface of the logarithm.
|
1943 |
+
|
1944 |
+
The formula also holds as stated
|
1945 |
+
for $z \in \mathbb{C}$ with $\Re(z) > 0$.
|
1946 |
+
By lifting to the principal branch, we obtain an analytic function on the
|
1947 |
+
cut complex plane.
|
1948 |
+
|
1949 |
+
Examples
|
1950 |
+
========
|
1951 |
+
|
1952 |
+
>>> from sympy import Ci
|
1953 |
+
>>> from sympy.abc import z
|
1954 |
+
|
1955 |
+
The cosine integral is a primitive of $\cos(z)/z$:
|
1956 |
+
|
1957 |
+
>>> Ci(z).diff(z)
|
1958 |
+
cos(z)/z
|
1959 |
+
|
1960 |
+
It has a logarithmic branch point at the origin:
|
1961 |
+
|
1962 |
+
>>> from sympy import exp_polar, I, pi
|
1963 |
+
>>> Ci(z*exp_polar(2*I*pi))
|
1964 |
+
Ci(z) + 2*I*pi
|
1965 |
+
|
1966 |
+
The cosine integral behaves somewhat like ordinary $\cos$ under
|
1967 |
+
multiplication by $i$:
|
1968 |
+
|
1969 |
+
>>> from sympy import polar_lift
|
1970 |
+
>>> Ci(polar_lift(I)*z)
|
1971 |
+
Chi(z) + I*pi/2
|
1972 |
+
>>> Ci(polar_lift(-1)*z)
|
1973 |
+
Ci(z) + I*pi
|
1974 |
+
|
1975 |
+
It can also be expressed in terms of exponential integrals:
|
1976 |
+
|
1977 |
+
>>> from sympy import expint
|
1978 |
+
>>> Ci(z).rewrite(expint)
|
1979 |
+
-expint(1, z*exp_polar(-I*pi/2))/2 - expint(1, z*exp_polar(I*pi/2))/2
|
1980 |
+
|
1981 |
+
See Also
|
1982 |
+
========
|
1983 |
+
|
1984 |
+
Si: Sine integral.
|
1985 |
+
Shi: Hyperbolic sine integral.
|
1986 |
+
Chi: Hyperbolic cosine integral.
|
1987 |
+
Ei: Exponential integral.
|
1988 |
+
expint: Generalised exponential integral.
|
1989 |
+
E1: Special case of the generalised exponential integral.
|
1990 |
+
li: Logarithmic integral.
|
1991 |
+
Li: Offset logarithmic integral.
|
1992 |
+
|
1993 |
+
References
|
1994 |
+
==========
|
1995 |
+
|
1996 |
+
.. [1] https://en.wikipedia.org/wiki/Trigonometric_integral
|
1997 |
+
|
1998 |
+
"""
|
1999 |
+
|
2000 |
+
_trigfunc = cos
|
2001 |
+
_atzero = S.ComplexInfinity
|
2002 |
+
|
2003 |
+
@classmethod
|
2004 |
+
def _atinf(cls):
|
2005 |
+
return S.Zero
|
2006 |
+
|
2007 |
+
@classmethod
|
2008 |
+
def _atneginf(cls):
|
2009 |
+
return I*pi
|
2010 |
+
|
2011 |
+
@classmethod
|
2012 |
+
def _minusfactor(cls, z):
|
2013 |
+
return Ci(z) + I*pi
|
2014 |
+
|
2015 |
+
@classmethod
|
2016 |
+
def _Ifactor(cls, z, sign):
|
2017 |
+
return Chi(z) + I*pi/2*sign
|
2018 |
+
|
2019 |
+
def _eval_rewrite_as_expint(self, z, **kwargs):
|
2020 |
+
return -(E1(polar_lift(I)*z) + E1(polar_lift(-I)*z))/2
|
2021 |
+
|
2022 |
+
def _eval_as_leading_term(self, x, logx=None, cdir=0):
|
2023 |
+
arg = self.args[0].as_leading_term(x, logx=logx, cdir=cdir)
|
2024 |
+
arg0 = arg.subs(x, 0)
|
2025 |
+
|
2026 |
+
if arg0 is S.NaN:
|
2027 |
+
arg0 = arg.limit(x, 0, dir='-' if re(cdir).is_negative else '+')
|
2028 |
+
if arg0.is_zero:
|
2029 |
+
c, e = arg.as_coeff_exponent(x)
|
2030 |
+
logx = log(x) if logx is None else logx
|
2031 |
+
return log(c) + e*logx + EulerGamma
|
2032 |
+
elif arg0.is_finite:
|
2033 |
+
return self.func(arg0)
|
2034 |
+
else:
|
2035 |
+
return self
|
2036 |
+
|
2037 |
+
def _eval_aseries(self, n, args0, x, logx):
|
2038 |
+
from sympy.series.order import Order
|
2039 |
+
point = args0[0]
|
2040 |
+
|
2041 |
+
# Expansion at oo
|
2042 |
+
if point is S.Infinity:
|
2043 |
+
z = self.args[0]
|
2044 |
+
p = [S.NegativeOne**k * factorial(2*k) / z**(2*k)
|
2045 |
+
for k in range(int((n - 1)/2))] + [Order(1/z**n, x)]
|
2046 |
+
q = [S.NegativeOne**k * factorial(2*k + 1) / z**(2*k + 1)
|
2047 |
+
for k in range(int(n/2) - 1)] + [Order(1/z**n, x)]
|
2048 |
+
return (sin(z)/z)*Add(*p) - (cos(z)/z)*Add(*q)
|
2049 |
+
|
2050 |
+
# All other points are not handled
|
2051 |
+
return super(Ci, self)._eval_aseries(n, args0, x, logx)
|
2052 |
+
|
2053 |
+
|
2054 |
+
class Shi(TrigonometricIntegral):
|
2055 |
+
r"""
|
2056 |
+
Sinh integral.
|
2057 |
+
|
2058 |
+
Explanation
|
2059 |
+
===========
|
2060 |
+
|
2061 |
+
This function is defined by
|
2062 |
+
|
2063 |
+
.. math:: \operatorname{Shi}(z) = \int_0^z \frac{\sinh{t}}{t} \mathrm{d}t.
|
2064 |
+
|
2065 |
+
It is an entire function.
|
2066 |
+
|
2067 |
+
Examples
|
2068 |
+
========
|
2069 |
+
|
2070 |
+
>>> from sympy import Shi
|
2071 |
+
>>> from sympy.abc import z
|
2072 |
+
|
2073 |
+
The Sinh integral is a primitive of $\sinh(z)/z$:
|
2074 |
+
|
2075 |
+
>>> Shi(z).diff(z)
|
2076 |
+
sinh(z)/z
|
2077 |
+
|
2078 |
+
It is unbranched:
|
2079 |
+
|
2080 |
+
>>> from sympy import exp_polar, I, pi
|
2081 |
+
>>> Shi(z*exp_polar(2*I*pi))
|
2082 |
+
Shi(z)
|
2083 |
+
|
2084 |
+
The $\sinh$ integral behaves much like ordinary $\sinh$ under
|
2085 |
+
multiplication by $i$:
|
2086 |
+
|
2087 |
+
>>> Shi(I*z)
|
2088 |
+
I*Si(z)
|
2089 |
+
>>> Shi(-z)
|
2090 |
+
-Shi(z)
|
2091 |
+
|
2092 |
+
It can also be expressed in terms of exponential integrals, but beware
|
2093 |
+
that the latter is branched:
|
2094 |
+
|
2095 |
+
>>> from sympy import expint
|
2096 |
+
>>> Shi(z).rewrite(expint)
|
2097 |
+
expint(1, z)/2 - expint(1, z*exp_polar(I*pi))/2 - I*pi/2
|
2098 |
+
|
2099 |
+
See Also
|
2100 |
+
========
|
2101 |
+
|
2102 |
+
Si: Sine integral.
|
2103 |
+
Ci: Cosine integral.
|
2104 |
+
Chi: Hyperbolic cosine integral.
|
2105 |
+
Ei: Exponential integral.
|
2106 |
+
expint: Generalised exponential integral.
|
2107 |
+
E1: Special case of the generalised exponential integral.
|
2108 |
+
li: Logarithmic integral.
|
2109 |
+
Li: Offset logarithmic integral.
|
2110 |
+
|
2111 |
+
References
|
2112 |
+
==========
|
2113 |
+
|
2114 |
+
.. [1] https://en.wikipedia.org/wiki/Trigonometric_integral
|
2115 |
+
|
2116 |
+
"""
|
2117 |
+
|
2118 |
+
_trigfunc = sinh
|
2119 |
+
_atzero = S.Zero
|
2120 |
+
|
2121 |
+
@classmethod
|
2122 |
+
def _atinf(cls):
|
2123 |
+
return S.Infinity
|
2124 |
+
|
2125 |
+
@classmethod
|
2126 |
+
def _atneginf(cls):
|
2127 |
+
return S.NegativeInfinity
|
2128 |
+
|
2129 |
+
@classmethod
|
2130 |
+
def _minusfactor(cls, z):
|
2131 |
+
return -Shi(z)
|
2132 |
+
|
2133 |
+
@classmethod
|
2134 |
+
def _Ifactor(cls, z, sign):
|
2135 |
+
return I*Si(z)*sign
|
2136 |
+
|
2137 |
+
def _eval_rewrite_as_expint(self, z, **kwargs):
|
2138 |
+
# XXX should we polarify z?
|
2139 |
+
return (E1(z) - E1(exp_polar(I*pi)*z))/2 - I*pi/2
|
2140 |
+
|
2141 |
+
def _eval_is_zero(self):
|
2142 |
+
z = self.args[0]
|
2143 |
+
if z.is_zero:
|
2144 |
+
return True
|
2145 |
+
|
2146 |
+
def _eval_as_leading_term(self, x, logx=None, cdir=0):
|
2147 |
+
arg = self.args[0].as_leading_term(x)
|
2148 |
+
arg0 = arg.subs(x, 0)
|
2149 |
+
|
2150 |
+
if arg0 is S.NaN:
|
2151 |
+
arg0 = arg.limit(x, 0, dir='-' if re(cdir).is_negative else '+')
|
2152 |
+
if arg0.is_zero:
|
2153 |
+
return arg
|
2154 |
+
elif not arg0.is_infinite:
|
2155 |
+
return self.func(arg0)
|
2156 |
+
else:
|
2157 |
+
return self
|
2158 |
+
|
2159 |
+
|
2160 |
+
class Chi(TrigonometricIntegral):
|
2161 |
+
r"""
|
2162 |
+
Cosh integral.
|
2163 |
+
|
2164 |
+
Explanation
|
2165 |
+
===========
|
2166 |
+
|
2167 |
+
This function is defined for positive $x$ by
|
2168 |
+
|
2169 |
+
.. math:: \operatorname{Chi}(x) = \gamma + \log{x}
|
2170 |
+
+ \int_0^x \frac{\cosh{t} - 1}{t} \mathrm{d}t,
|
2171 |
+
|
2172 |
+
where $\gamma$ is the Euler-Mascheroni constant.
|
2173 |
+
|
2174 |
+
We have
|
2175 |
+
|
2176 |
+
.. math:: \operatorname{Chi}(z) = \operatorname{Ci}\left(e^{i \pi/2}z\right)
|
2177 |
+
- i\frac{\pi}{2},
|
2178 |
+
|
2179 |
+
which holds for all polar $z$ and thus provides an analytic
|
2180 |
+
continuation to the Riemann surface of the logarithm.
|
2181 |
+
By lifting to the principal branch we obtain an analytic function on the
|
2182 |
+
cut complex plane.
|
2183 |
+
|
2184 |
+
Examples
|
2185 |
+
========
|
2186 |
+
|
2187 |
+
>>> from sympy import Chi
|
2188 |
+
>>> from sympy.abc import z
|
2189 |
+
|
2190 |
+
The $\cosh$ integral is a primitive of $\cosh(z)/z$:
|
2191 |
+
|
2192 |
+
>>> Chi(z).diff(z)
|
2193 |
+
cosh(z)/z
|
2194 |
+
|
2195 |
+
It has a logarithmic branch point at the origin:
|
2196 |
+
|
2197 |
+
>>> from sympy import exp_polar, I, pi
|
2198 |
+
>>> Chi(z*exp_polar(2*I*pi))
|
2199 |
+
Chi(z) + 2*I*pi
|
2200 |
+
|
2201 |
+
The $\cosh$ integral behaves somewhat like ordinary $\cosh$ under
|
2202 |
+
multiplication by $i$:
|
2203 |
+
|
2204 |
+
>>> from sympy import polar_lift
|
2205 |
+
>>> Chi(polar_lift(I)*z)
|
2206 |
+
Ci(z) + I*pi/2
|
2207 |
+
>>> Chi(polar_lift(-1)*z)
|
2208 |
+
Chi(z) + I*pi
|
2209 |
+
|
2210 |
+
It can also be expressed in terms of exponential integrals:
|
2211 |
+
|
2212 |
+
>>> from sympy import expint
|
2213 |
+
>>> Chi(z).rewrite(expint)
|
2214 |
+
-expint(1, z)/2 - expint(1, z*exp_polar(I*pi))/2 - I*pi/2
|
2215 |
+
|
2216 |
+
See Also
|
2217 |
+
========
|
2218 |
+
|
2219 |
+
Si: Sine integral.
|
2220 |
+
Ci: Cosine integral.
|
2221 |
+
Shi: Hyperbolic sine integral.
|
2222 |
+
Ei: Exponential integral.
|
2223 |
+
expint: Generalised exponential integral.
|
2224 |
+
E1: Special case of the generalised exponential integral.
|
2225 |
+
li: Logarithmic integral.
|
2226 |
+
Li: Offset logarithmic integral.
|
2227 |
+
|
2228 |
+
References
|
2229 |
+
==========
|
2230 |
+
|
2231 |
+
.. [1] https://en.wikipedia.org/wiki/Trigonometric_integral
|
2232 |
+
|
2233 |
+
"""
|
2234 |
+
|
2235 |
+
_trigfunc = cosh
|
2236 |
+
_atzero = S.ComplexInfinity
|
2237 |
+
|
2238 |
+
@classmethod
|
2239 |
+
def _atinf(cls):
|
2240 |
+
return S.Infinity
|
2241 |
+
|
2242 |
+
@classmethod
|
2243 |
+
def _atneginf(cls):
|
2244 |
+
return S.Infinity
|
2245 |
+
|
2246 |
+
@classmethod
|
2247 |
+
def _minusfactor(cls, z):
|
2248 |
+
return Chi(z) + I*pi
|
2249 |
+
|
2250 |
+
@classmethod
|
2251 |
+
def _Ifactor(cls, z, sign):
|
2252 |
+
return Ci(z) + I*pi/2*sign
|
2253 |
+
|
2254 |
+
def _eval_rewrite_as_expint(self, z, **kwargs):
|
2255 |
+
return -I*pi/2 - (E1(z) + E1(exp_polar(I*pi)*z))/2
|
2256 |
+
|
2257 |
+
def _eval_as_leading_term(self, x, logx=None, cdir=0):
|
2258 |
+
arg = self.args[0].as_leading_term(x, logx=logx, cdir=cdir)
|
2259 |
+
arg0 = arg.subs(x, 0)
|
2260 |
+
|
2261 |
+
if arg0 is S.NaN:
|
2262 |
+
arg0 = arg.limit(x, 0, dir='-' if re(cdir).is_negative else '+')
|
2263 |
+
if arg0.is_zero:
|
2264 |
+
c, e = arg.as_coeff_exponent(x)
|
2265 |
+
logx = log(x) if logx is None else logx
|
2266 |
+
return log(c) + e*logx + EulerGamma
|
2267 |
+
elif arg0.is_finite:
|
2268 |
+
return self.func(arg0)
|
2269 |
+
else:
|
2270 |
+
return self
|
2271 |
+
|
2272 |
+
|
2273 |
+
###############################################################################
|
2274 |
+
#################### FRESNEL INTEGRALS ########################################
|
2275 |
+
###############################################################################
|
2276 |
+
|
2277 |
+
class FresnelIntegral(Function):
|
2278 |
+
""" Base class for the Fresnel integrals."""
|
2279 |
+
|
2280 |
+
unbranched = True
|
2281 |
+
|
2282 |
+
@classmethod
|
2283 |
+
def eval(cls, z):
|
2284 |
+
# Values at positive infinities signs
|
2285 |
+
# if any were extracted automatically
|
2286 |
+
if z is S.Infinity:
|
2287 |
+
return S.Half
|
2288 |
+
|
2289 |
+
# Value at zero
|
2290 |
+
if z.is_zero:
|
2291 |
+
return S.Zero
|
2292 |
+
|
2293 |
+
# Try to pull out factors of -1 and I
|
2294 |
+
prefact = S.One
|
2295 |
+
newarg = z
|
2296 |
+
changed = False
|
2297 |
+
|
2298 |
+
nz = newarg.extract_multiplicatively(-1)
|
2299 |
+
if nz is not None:
|
2300 |
+
prefact = -prefact
|
2301 |
+
newarg = nz
|
2302 |
+
changed = True
|
2303 |
+
|
2304 |
+
nz = newarg.extract_multiplicatively(I)
|
2305 |
+
if nz is not None:
|
2306 |
+
prefact = cls._sign*I*prefact
|
2307 |
+
newarg = nz
|
2308 |
+
changed = True
|
2309 |
+
|
2310 |
+
if changed:
|
2311 |
+
return prefact*cls(newarg)
|
2312 |
+
|
2313 |
+
def fdiff(self, argindex=1):
|
2314 |
+
if argindex == 1:
|
2315 |
+
return self._trigfunc(S.Half*pi*self.args[0]**2)
|
2316 |
+
else:
|
2317 |
+
raise ArgumentIndexError(self, argindex)
|
2318 |
+
|
2319 |
+
def _eval_is_extended_real(self):
|
2320 |
+
return self.args[0].is_extended_real
|
2321 |
+
|
2322 |
+
_eval_is_finite = _eval_is_extended_real
|
2323 |
+
|
2324 |
+
def _eval_is_zero(self):
|
2325 |
+
return self.args[0].is_zero
|
2326 |
+
|
2327 |
+
def _eval_conjugate(self):
|
2328 |
+
return self.func(self.args[0].conjugate())
|
2329 |
+
|
2330 |
+
as_real_imag = real_to_real_as_real_imag
|
2331 |
+
|
2332 |
+
|
2333 |
+
class fresnels(FresnelIntegral):
|
2334 |
+
r"""
|
2335 |
+
Fresnel integral S.
|
2336 |
+
|
2337 |
+
Explanation
|
2338 |
+
===========
|
2339 |
+
|
2340 |
+
This function is defined by
|
2341 |
+
|
2342 |
+
.. math:: \operatorname{S}(z) = \int_0^z \sin{\frac{\pi}{2} t^2} \mathrm{d}t.
|
2343 |
+
|
2344 |
+
It is an entire function.
|
2345 |
+
|
2346 |
+
Examples
|
2347 |
+
========
|
2348 |
+
|
2349 |
+
>>> from sympy import I, oo, fresnels
|
2350 |
+
>>> from sympy.abc import z
|
2351 |
+
|
2352 |
+
Several special values are known:
|
2353 |
+
|
2354 |
+
>>> fresnels(0)
|
2355 |
+
0
|
2356 |
+
>>> fresnels(oo)
|
2357 |
+
1/2
|
2358 |
+
>>> fresnels(-oo)
|
2359 |
+
-1/2
|
2360 |
+
>>> fresnels(I*oo)
|
2361 |
+
-I/2
|
2362 |
+
>>> fresnels(-I*oo)
|
2363 |
+
I/2
|
2364 |
+
|
2365 |
+
In general one can pull out factors of -1 and $i$ from the argument:
|
2366 |
+
|
2367 |
+
>>> fresnels(-z)
|
2368 |
+
-fresnels(z)
|
2369 |
+
>>> fresnels(I*z)
|
2370 |
+
-I*fresnels(z)
|
2371 |
+
|
2372 |
+
The Fresnel S integral obeys the mirror symmetry
|
2373 |
+
$\overline{S(z)} = S(\bar{z})$:
|
2374 |
+
|
2375 |
+
>>> from sympy import conjugate
|
2376 |
+
>>> conjugate(fresnels(z))
|
2377 |
+
fresnels(conjugate(z))
|
2378 |
+
|
2379 |
+
Differentiation with respect to $z$ is supported:
|
2380 |
+
|
2381 |
+
>>> from sympy import diff
|
2382 |
+
>>> diff(fresnels(z), z)
|
2383 |
+
sin(pi*z**2/2)
|
2384 |
+
|
2385 |
+
Defining the Fresnel functions via an integral:
|
2386 |
+
|
2387 |
+
>>> from sympy import integrate, pi, sin, expand_func
|
2388 |
+
>>> integrate(sin(pi*z**2/2), z)
|
2389 |
+
3*fresnels(z)*gamma(3/4)/(4*gamma(7/4))
|
2390 |
+
>>> expand_func(integrate(sin(pi*z**2/2), z))
|
2391 |
+
fresnels(z)
|
2392 |
+
|
2393 |
+
We can numerically evaluate the Fresnel integral to arbitrary precision
|
2394 |
+
on the whole complex plane:
|
2395 |
+
|
2396 |
+
>>> fresnels(2).evalf(30)
|
2397 |
+
0.343415678363698242195300815958
|
2398 |
+
|
2399 |
+
>>> fresnels(-2*I).evalf(30)
|
2400 |
+
0.343415678363698242195300815958*I
|
2401 |
+
|
2402 |
+
See Also
|
2403 |
+
========
|
2404 |
+
|
2405 |
+
fresnelc: Fresnel cosine integral.
|
2406 |
+
|
2407 |
+
References
|
2408 |
+
==========
|
2409 |
+
|
2410 |
+
.. [1] https://en.wikipedia.org/wiki/Fresnel_integral
|
2411 |
+
.. [2] https://dlmf.nist.gov/7
|
2412 |
+
.. [3] https://mathworld.wolfram.com/FresnelIntegrals.html
|
2413 |
+
.. [4] https://functions.wolfram.com/GammaBetaErf/FresnelS
|
2414 |
+
.. [5] The converging factors for the fresnel integrals
|
2415 |
+
by John W. Wrench Jr. and Vicki Alley
|
2416 |
+
|
2417 |
+
"""
|
2418 |
+
_trigfunc = sin
|
2419 |
+
_sign = -S.One
|
2420 |
+
|
2421 |
+
@staticmethod
|
2422 |
+
@cacheit
|
2423 |
+
def taylor_term(n, x, *previous_terms):
|
2424 |
+
if n < 0:
|
2425 |
+
return S.Zero
|
2426 |
+
else:
|
2427 |
+
x = sympify(x)
|
2428 |
+
if len(previous_terms) > 1:
|
2429 |
+
p = previous_terms[-1]
|
2430 |
+
return (-pi**2*x**4*(4*n - 1)/(8*n*(2*n + 1)*(4*n + 3))) * p
|
2431 |
+
else:
|
2432 |
+
return x**3 * (-x**4)**n * (S(2)**(-2*n - 1)*pi**(2*n + 1)) / ((4*n + 3)*factorial(2*n + 1))
|
2433 |
+
|
2434 |
+
def _eval_rewrite_as_erf(self, z, **kwargs):
|
2435 |
+
return (S.One + I)/4 * (erf((S.One + I)/2*sqrt(pi)*z) - I*erf((S.One - I)/2*sqrt(pi)*z))
|
2436 |
+
|
2437 |
+
def _eval_rewrite_as_hyper(self, z, **kwargs):
|
2438 |
+
return pi*z**3/6 * hyper([Rational(3, 4)], [Rational(3, 2), Rational(7, 4)], -pi**2*z**4/16)
|
2439 |
+
|
2440 |
+
def _eval_rewrite_as_meijerg(self, z, **kwargs):
|
2441 |
+
return (pi*z**Rational(9, 4) / (sqrt(2)*(z**2)**Rational(3, 4)*(-z)**Rational(3, 4))
|
2442 |
+
* meijerg([], [1], [Rational(3, 4)], [Rational(1, 4), 0], -pi**2*z**4/16))
|
2443 |
+
|
2444 |
+
def _eval_as_leading_term(self, x, logx=None, cdir=0):
|
2445 |
+
from sympy.series.order import Order
|
2446 |
+
arg = self.args[0].as_leading_term(x, logx=logx, cdir=cdir)
|
2447 |
+
arg0 = arg.subs(x, 0)
|
2448 |
+
|
2449 |
+
if arg0 is S.ComplexInfinity:
|
2450 |
+
arg0 = arg.limit(x, 0, dir='-' if re(cdir).is_negative else '+')
|
2451 |
+
if arg0.is_zero:
|
2452 |
+
return pi*arg**3/6
|
2453 |
+
elif arg0 in [S.Infinity, S.NegativeInfinity]:
|
2454 |
+
s = 1 if arg0 is S.Infinity else -1
|
2455 |
+
return s*S.Half + Order(x, x)
|
2456 |
+
else:
|
2457 |
+
return self.func(arg0)
|
2458 |
+
|
2459 |
+
def _eval_aseries(self, n, args0, x, logx):
|
2460 |
+
from sympy.series.order import Order
|
2461 |
+
point = args0[0]
|
2462 |
+
|
2463 |
+
# Expansion at oo and -oo
|
2464 |
+
if point in [S.Infinity, -S.Infinity]:
|
2465 |
+
z = self.args[0]
|
2466 |
+
|
2467 |
+
# expansion of S(x) = S1(x*sqrt(pi/2)), see reference[5] page 1-8
|
2468 |
+
# as only real infinities are dealt with, sin and cos are O(1)
|
2469 |
+
p = [S.NegativeOne**k * factorial(4*k + 1) /
|
2470 |
+
(2**(2*k + 2) * z**(4*k + 3) * 2**(2*k)*factorial(2*k))
|
2471 |
+
for k in range(0, n) if 4*k + 3 < n]
|
2472 |
+
q = [1/(2*z)] + [S.NegativeOne**k * factorial(4*k - 1) /
|
2473 |
+
(2**(2*k + 1) * z**(4*k + 1) * 2**(2*k - 1)*factorial(2*k - 1))
|
2474 |
+
for k in range(1, n) if 4*k + 1 < n]
|
2475 |
+
|
2476 |
+
p = [-sqrt(2/pi)*t for t in p]
|
2477 |
+
q = [-sqrt(2/pi)*t for t in q]
|
2478 |
+
s = 1 if point is S.Infinity else -1
|
2479 |
+
# The expansion at oo is 1/2 + some odd powers of z
|
2480 |
+
# To get the expansion at -oo, replace z by -z and flip the sign
|
2481 |
+
# The result -1/2 + the same odd powers of z as before.
|
2482 |
+
return s*S.Half + (sin(z**2)*Add(*p) + cos(z**2)*Add(*q)
|
2483 |
+
).subs(x, sqrt(2/pi)*x) + Order(1/z**n, x)
|
2484 |
+
|
2485 |
+
# All other points are not handled
|
2486 |
+
return super()._eval_aseries(n, args0, x, logx)
|
2487 |
+
|
2488 |
+
|
2489 |
+
class fresnelc(FresnelIntegral):
|
2490 |
+
r"""
|
2491 |
+
Fresnel integral C.
|
2492 |
+
|
2493 |
+
Explanation
|
2494 |
+
===========
|
2495 |
+
|
2496 |
+
This function is defined by
|
2497 |
+
|
2498 |
+
.. math:: \operatorname{C}(z) = \int_0^z \cos{\frac{\pi}{2} t^2} \mathrm{d}t.
|
2499 |
+
|
2500 |
+
It is an entire function.
|
2501 |
+
|
2502 |
+
Examples
|
2503 |
+
========
|
2504 |
+
|
2505 |
+
>>> from sympy import I, oo, fresnelc
|
2506 |
+
>>> from sympy.abc import z
|
2507 |
+
|
2508 |
+
Several special values are known:
|
2509 |
+
|
2510 |
+
>>> fresnelc(0)
|
2511 |
+
0
|
2512 |
+
>>> fresnelc(oo)
|
2513 |
+
1/2
|
2514 |
+
>>> fresnelc(-oo)
|
2515 |
+
-1/2
|
2516 |
+
>>> fresnelc(I*oo)
|
2517 |
+
I/2
|
2518 |
+
>>> fresnelc(-I*oo)
|
2519 |
+
-I/2
|
2520 |
+
|
2521 |
+
In general one can pull out factors of -1 and $i$ from the argument:
|
2522 |
+
|
2523 |
+
>>> fresnelc(-z)
|
2524 |
+
-fresnelc(z)
|
2525 |
+
>>> fresnelc(I*z)
|
2526 |
+
I*fresnelc(z)
|
2527 |
+
|
2528 |
+
The Fresnel C integral obeys the mirror symmetry
|
2529 |
+
$\overline{C(z)} = C(\bar{z})$:
|
2530 |
+
|
2531 |
+
>>> from sympy import conjugate
|
2532 |
+
>>> conjugate(fresnelc(z))
|
2533 |
+
fresnelc(conjugate(z))
|
2534 |
+
|
2535 |
+
Differentiation with respect to $z$ is supported:
|
2536 |
+
|
2537 |
+
>>> from sympy import diff
|
2538 |
+
>>> diff(fresnelc(z), z)
|
2539 |
+
cos(pi*z**2/2)
|
2540 |
+
|
2541 |
+
Defining the Fresnel functions via an integral:
|
2542 |
+
|
2543 |
+
>>> from sympy import integrate, pi, cos, expand_func
|
2544 |
+
>>> integrate(cos(pi*z**2/2), z)
|
2545 |
+
fresnelc(z)*gamma(1/4)/(4*gamma(5/4))
|
2546 |
+
>>> expand_func(integrate(cos(pi*z**2/2), z))
|
2547 |
+
fresnelc(z)
|
2548 |
+
|
2549 |
+
We can numerically evaluate the Fresnel integral to arbitrary precision
|
2550 |
+
on the whole complex plane:
|
2551 |
+
|
2552 |
+
>>> fresnelc(2).evalf(30)
|
2553 |
+
0.488253406075340754500223503357
|
2554 |
+
|
2555 |
+
>>> fresnelc(-2*I).evalf(30)
|
2556 |
+
-0.488253406075340754500223503357*I
|
2557 |
+
|
2558 |
+
See Also
|
2559 |
+
========
|
2560 |
+
|
2561 |
+
fresnels: Fresnel sine integral.
|
2562 |
+
|
2563 |
+
References
|
2564 |
+
==========
|
2565 |
+
|
2566 |
+
.. [1] https://en.wikipedia.org/wiki/Fresnel_integral
|
2567 |
+
.. [2] https://dlmf.nist.gov/7
|
2568 |
+
.. [3] https://mathworld.wolfram.com/FresnelIntegrals.html
|
2569 |
+
.. [4] https://functions.wolfram.com/GammaBetaErf/FresnelC
|
2570 |
+
.. [5] The converging factors for the fresnel integrals
|
2571 |
+
by John W. Wrench Jr. and Vicki Alley
|
2572 |
+
|
2573 |
+
"""
|
2574 |
+
_trigfunc = cos
|
2575 |
+
_sign = S.One
|
2576 |
+
|
2577 |
+
@staticmethod
|
2578 |
+
@cacheit
|
2579 |
+
def taylor_term(n, x, *previous_terms):
|
2580 |
+
if n < 0:
|
2581 |
+
return S.Zero
|
2582 |
+
else:
|
2583 |
+
x = sympify(x)
|
2584 |
+
if len(previous_terms) > 1:
|
2585 |
+
p = previous_terms[-1]
|
2586 |
+
return (-pi**2*x**4*(4*n - 3)/(8*n*(2*n - 1)*(4*n + 1))) * p
|
2587 |
+
else:
|
2588 |
+
return x * (-x**4)**n * (S(2)**(-2*n)*pi**(2*n)) / ((4*n + 1)*factorial(2*n))
|
2589 |
+
|
2590 |
+
def _eval_rewrite_as_erf(self, z, **kwargs):
|
2591 |
+
return (S.One - I)/4 * (erf((S.One + I)/2*sqrt(pi)*z) + I*erf((S.One - I)/2*sqrt(pi)*z))
|
2592 |
+
|
2593 |
+
def _eval_rewrite_as_hyper(self, z, **kwargs):
|
2594 |
+
return z * hyper([Rational(1, 4)], [S.Half, Rational(5, 4)], -pi**2*z**4/16)
|
2595 |
+
|
2596 |
+
def _eval_rewrite_as_meijerg(self, z, **kwargs):
|
2597 |
+
return (pi*z**Rational(3, 4) / (sqrt(2)*root(z**2, 4)*root(-z, 4))
|
2598 |
+
* meijerg([], [1], [Rational(1, 4)], [Rational(3, 4), 0], -pi**2*z**4/16))
|
2599 |
+
|
2600 |
+
def _eval_as_leading_term(self, x, logx=None, cdir=0):
|
2601 |
+
from sympy.series.order import Order
|
2602 |
+
arg = self.args[0].as_leading_term(x, logx=logx, cdir=cdir)
|
2603 |
+
arg0 = arg.subs(x, 0)
|
2604 |
+
|
2605 |
+
if arg0 is S.ComplexInfinity:
|
2606 |
+
arg0 = arg.limit(x, 0, dir='-' if re(cdir).is_negative else '+')
|
2607 |
+
if arg0.is_zero:
|
2608 |
+
return arg
|
2609 |
+
elif arg0 in [S.Infinity, S.NegativeInfinity]:
|
2610 |
+
s = 1 if arg0 is S.Infinity else -1
|
2611 |
+
return s*S.Half + Order(x, x)
|
2612 |
+
else:
|
2613 |
+
return self.func(arg0)
|
2614 |
+
|
2615 |
+
def _eval_aseries(self, n, args0, x, logx):
|
2616 |
+
from sympy.series.order import Order
|
2617 |
+
point = args0[0]
|
2618 |
+
|
2619 |
+
# Expansion at oo
|
2620 |
+
if point in [S.Infinity, -S.Infinity]:
|
2621 |
+
z = self.args[0]
|
2622 |
+
|
2623 |
+
# expansion of C(x) = C1(x*sqrt(pi/2)), see reference[5] page 1-8
|
2624 |
+
# as only real infinities are dealt with, sin and cos are O(1)
|
2625 |
+
p = [S.NegativeOne**k * factorial(4*k + 1) /
|
2626 |
+
(2**(2*k + 2) * z**(4*k + 3) * 2**(2*k)*factorial(2*k))
|
2627 |
+
for k in range(n) if 4*k + 3 < n]
|
2628 |
+
q = [1/(2*z)] + [S.NegativeOne**k * factorial(4*k - 1) /
|
2629 |
+
(2**(2*k + 1) * z**(4*k + 1) * 2**(2*k - 1)*factorial(2*k - 1))
|
2630 |
+
for k in range(1, n) if 4*k + 1 < n]
|
2631 |
+
|
2632 |
+
p = [-sqrt(2/pi)*t for t in p]
|
2633 |
+
q = [ sqrt(2/pi)*t for t in q]
|
2634 |
+
s = 1 if point is S.Infinity else -1
|
2635 |
+
# The expansion at oo is 1/2 + some odd powers of z
|
2636 |
+
# To get the expansion at -oo, replace z by -z and flip the sign
|
2637 |
+
# The result -1/2 + the same odd powers of z as before.
|
2638 |
+
return s*S.Half + (cos(z**2)*Add(*p) + sin(z**2)*Add(*q)
|
2639 |
+
).subs(x, sqrt(2/pi)*x) + Order(1/z**n, x)
|
2640 |
+
|
2641 |
+
# All other points are not handled
|
2642 |
+
return super()._eval_aseries(n, args0, x, logx)
|
2643 |
+
|
2644 |
+
|
2645 |
+
###############################################################################
|
2646 |
+
#################### HELPER FUNCTIONS #########################################
|
2647 |
+
###############################################################################
|
2648 |
+
|
2649 |
+
|
2650 |
+
class _erfs(Function):
|
2651 |
+
"""
|
2652 |
+
Helper function to make the $\\mathrm{erf}(z)$ function
|
2653 |
+
tractable for the Gruntz algorithm.
|
2654 |
+
|
2655 |
+
"""
|
2656 |
+
@classmethod
|
2657 |
+
def eval(cls, arg):
|
2658 |
+
if arg.is_zero:
|
2659 |
+
return S.One
|
2660 |
+
|
2661 |
+
def _eval_aseries(self, n, args0, x, logx):
|
2662 |
+
from sympy.series.order import Order
|
2663 |
+
point = args0[0]
|
2664 |
+
|
2665 |
+
# Expansion at oo
|
2666 |
+
if point is S.Infinity:
|
2667 |
+
z = self.args[0]
|
2668 |
+
l = [1/sqrt(pi) * factorial(2*k)*(-S(
|
2669 |
+
4))**(-k)/factorial(k) * (1/z)**(2*k + 1) for k in range(n)]
|
2670 |
+
o = Order(1/z**(2*n + 1), x)
|
2671 |
+
# It is very inefficient to first add the order and then do the nseries
|
2672 |
+
return (Add(*l))._eval_nseries(x, n, logx) + o
|
2673 |
+
|
2674 |
+
# Expansion at I*oo
|
2675 |
+
t = point.extract_multiplicatively(I)
|
2676 |
+
if t is S.Infinity:
|
2677 |
+
z = self.args[0]
|
2678 |
+
# TODO: is the series really correct?
|
2679 |
+
l = [1/sqrt(pi) * factorial(2*k)*(-S(
|
2680 |
+
4))**(-k)/factorial(k) * (1/z)**(2*k + 1) for k in range(n)]
|
2681 |
+
o = Order(1/z**(2*n + 1), x)
|
2682 |
+
# It is very inefficient to first add the order and then do the nseries
|
2683 |
+
return (Add(*l))._eval_nseries(x, n, logx) + o
|
2684 |
+
|
2685 |
+
# All other points are not handled
|
2686 |
+
return super()._eval_aseries(n, args0, x, logx)
|
2687 |
+
|
2688 |
+
def fdiff(self, argindex=1):
|
2689 |
+
if argindex == 1:
|
2690 |
+
z = self.args[0]
|
2691 |
+
return -2/sqrt(pi) + 2*z*_erfs(z)
|
2692 |
+
else:
|
2693 |
+
raise ArgumentIndexError(self, argindex)
|
2694 |
+
|
2695 |
+
def _eval_rewrite_as_intractable(self, z, **kwargs):
|
2696 |
+
return (S.One - erf(z))*exp(z**2)
|
2697 |
+
|
2698 |
+
|
2699 |
+
class _eis(Function):
|
2700 |
+
"""
|
2701 |
+
Helper function to make the $\\mathrm{Ei}(z)$ and $\\mathrm{li}(z)$
|
2702 |
+
functions tractable for the Gruntz algorithm.
|
2703 |
+
|
2704 |
+
"""
|
2705 |
+
|
2706 |
+
|
2707 |
+
def _eval_aseries(self, n, args0, x, logx):
|
2708 |
+
from sympy.series.order import Order
|
2709 |
+
if args0[0] != S.Infinity:
|
2710 |
+
return super(_erfs, self)._eval_aseries(n, args0, x, logx)
|
2711 |
+
|
2712 |
+
z = self.args[0]
|
2713 |
+
l = [factorial(k) * (1/z)**(k + 1) for k in range(n)]
|
2714 |
+
o = Order(1/z**(n + 1), x)
|
2715 |
+
# It is very inefficient to first add the order and then do the nseries
|
2716 |
+
return (Add(*l))._eval_nseries(x, n, logx) + o
|
2717 |
+
|
2718 |
+
|
2719 |
+
def fdiff(self, argindex=1):
|
2720 |
+
if argindex == 1:
|
2721 |
+
z = self.args[0]
|
2722 |
+
return S.One / z - _eis(z)
|
2723 |
+
else:
|
2724 |
+
raise ArgumentIndexError(self, argindex)
|
2725 |
+
|
2726 |
+
def _eval_rewrite_as_intractable(self, z, **kwargs):
|
2727 |
+
return exp(-z)*Ei(z)
|
2728 |
+
|
2729 |
+
def _eval_as_leading_term(self, x, logx=None, cdir=0):
|
2730 |
+
x0 = self.args[0].limit(x, 0)
|
2731 |
+
if x0.is_zero:
|
2732 |
+
f = self._eval_rewrite_as_intractable(*self.args)
|
2733 |
+
return f._eval_as_leading_term(x, logx=logx, cdir=cdir)
|
2734 |
+
return super()._eval_as_leading_term(x, logx=logx, cdir=cdir)
|
2735 |
+
|
2736 |
+
def _eval_nseries(self, x, n, logx, cdir=0):
|
2737 |
+
x0 = self.args[0].limit(x, 0)
|
2738 |
+
if x0.is_zero:
|
2739 |
+
f = self._eval_rewrite_as_intractable(*self.args)
|
2740 |
+
return f._eval_nseries(x, n, logx)
|
2741 |
+
return super()._eval_nseries(x, n, logx)
|
venv/lib/python3.10/site-packages/sympy/functions/special/gamma_functions.py
ADDED
@@ -0,0 +1,1344 @@
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|
1 |
+
from math import prod
|
2 |
+
|
3 |
+
from sympy.core import Add, S, Dummy, expand_func
|
4 |
+
from sympy.core.expr import Expr
|
5 |
+
from sympy.core.function import Function, ArgumentIndexError, PoleError
|
6 |
+
from sympy.core.logic import fuzzy_and, fuzzy_not
|
7 |
+
from sympy.core.numbers import Rational, pi, oo, I
|
8 |
+
from sympy.core.power import Pow
|
9 |
+
from sympy.functions.special.zeta_functions import zeta
|
10 |
+
from sympy.functions.special.error_functions import erf, erfc, Ei
|
11 |
+
from sympy.functions.elementary.complexes import re, unpolarify
|
12 |
+
from sympy.functions.elementary.exponential import exp, log
|
13 |
+
from sympy.functions.elementary.integers import ceiling, floor
|
14 |
+
from sympy.functions.elementary.miscellaneous import sqrt
|
15 |
+
from sympy.functions.elementary.trigonometric import sin, cos, cot
|
16 |
+
from sympy.functions.combinatorial.numbers import bernoulli, harmonic
|
17 |
+
from sympy.functions.combinatorial.factorials import factorial, rf, RisingFactorial
|
18 |
+
from sympy.utilities.misc import as_int
|
19 |
+
|
20 |
+
from mpmath import mp, workprec
|
21 |
+
from mpmath.libmp.libmpf import prec_to_dps
|
22 |
+
|
23 |
+
def intlike(n):
|
24 |
+
try:
|
25 |
+
as_int(n, strict=False)
|
26 |
+
return True
|
27 |
+
except ValueError:
|
28 |
+
return False
|
29 |
+
|
30 |
+
###############################################################################
|
31 |
+
############################ COMPLETE GAMMA FUNCTION ##########################
|
32 |
+
###############################################################################
|
33 |
+
|
34 |
+
class gamma(Function):
|
35 |
+
r"""
|
36 |
+
The gamma function
|
37 |
+
|
38 |
+
.. math::
|
39 |
+
\Gamma(x) := \int^{\infty}_{0} t^{x-1} e^{-t} \mathrm{d}t.
|
40 |
+
|
41 |
+
Explanation
|
42 |
+
===========
|
43 |
+
|
44 |
+
The ``gamma`` function implements the function which passes through the
|
45 |
+
values of the factorial function (i.e., $\Gamma(n) = (n - 1)!$ when n is
|
46 |
+
an integer). More generally, $\Gamma(z)$ is defined in the whole complex
|
47 |
+
plane except at the negative integers where there are simple poles.
|
48 |
+
|
49 |
+
Examples
|
50 |
+
========
|
51 |
+
|
52 |
+
>>> from sympy import S, I, pi, gamma
|
53 |
+
>>> from sympy.abc import x
|
54 |
+
|
55 |
+
Several special values are known:
|
56 |
+
|
57 |
+
>>> gamma(1)
|
58 |
+
1
|
59 |
+
>>> gamma(4)
|
60 |
+
6
|
61 |
+
>>> gamma(S(3)/2)
|
62 |
+
sqrt(pi)/2
|
63 |
+
|
64 |
+
The ``gamma`` function obeys the mirror symmetry:
|
65 |
+
|
66 |
+
>>> from sympy import conjugate
|
67 |
+
>>> conjugate(gamma(x))
|
68 |
+
gamma(conjugate(x))
|
69 |
+
|
70 |
+
Differentiation with respect to $x$ is supported:
|
71 |
+
|
72 |
+
>>> from sympy import diff
|
73 |
+
>>> diff(gamma(x), x)
|
74 |
+
gamma(x)*polygamma(0, x)
|
75 |
+
|
76 |
+
Series expansion is also supported:
|
77 |
+
|
78 |
+
>>> from sympy import series
|
79 |
+
>>> series(gamma(x), x, 0, 3)
|
80 |
+
1/x - EulerGamma + x*(EulerGamma**2/2 + pi**2/12) + x**2*(-EulerGamma*pi**2/12 - zeta(3)/3 - EulerGamma**3/6) + O(x**3)
|
81 |
+
|
82 |
+
We can numerically evaluate the ``gamma`` function to arbitrary precision
|
83 |
+
on the whole complex plane:
|
84 |
+
|
85 |
+
>>> gamma(pi).evalf(40)
|
86 |
+
2.288037795340032417959588909060233922890
|
87 |
+
>>> gamma(1+I).evalf(20)
|
88 |
+
0.49801566811835604271 - 0.15494982830181068512*I
|
89 |
+
|
90 |
+
See Also
|
91 |
+
========
|
92 |
+
|
93 |
+
lowergamma: Lower incomplete gamma function.
|
94 |
+
uppergamma: Upper incomplete gamma function.
|
95 |
+
polygamma: Polygamma function.
|
96 |
+
loggamma: Log Gamma function.
|
97 |
+
digamma: Digamma function.
|
98 |
+
trigamma: Trigamma function.
|
99 |
+
beta: Euler Beta function.
|
100 |
+
|
101 |
+
References
|
102 |
+
==========
|
103 |
+
|
104 |
+
.. [1] https://en.wikipedia.org/wiki/Gamma_function
|
105 |
+
.. [2] https://dlmf.nist.gov/5
|
106 |
+
.. [3] https://mathworld.wolfram.com/GammaFunction.html
|
107 |
+
.. [4] https://functions.wolfram.com/GammaBetaErf/Gamma/
|
108 |
+
|
109 |
+
"""
|
110 |
+
|
111 |
+
unbranched = True
|
112 |
+
_singularities = (S.ComplexInfinity,)
|
113 |
+
|
114 |
+
def fdiff(self, argindex=1):
|
115 |
+
if argindex == 1:
|
116 |
+
return self.func(self.args[0])*polygamma(0, self.args[0])
|
117 |
+
else:
|
118 |
+
raise ArgumentIndexError(self, argindex)
|
119 |
+
|
120 |
+
@classmethod
|
121 |
+
def eval(cls, arg):
|
122 |
+
if arg.is_Number:
|
123 |
+
if arg is S.NaN:
|
124 |
+
return S.NaN
|
125 |
+
elif arg is oo:
|
126 |
+
return oo
|
127 |
+
elif intlike(arg):
|
128 |
+
if arg.is_positive:
|
129 |
+
return factorial(arg - 1)
|
130 |
+
else:
|
131 |
+
return S.ComplexInfinity
|
132 |
+
elif arg.is_Rational:
|
133 |
+
if arg.q == 2:
|
134 |
+
n = abs(arg.p) // arg.q
|
135 |
+
|
136 |
+
if arg.is_positive:
|
137 |
+
k, coeff = n, S.One
|
138 |
+
else:
|
139 |
+
n = k = n + 1
|
140 |
+
|
141 |
+
if n & 1 == 0:
|
142 |
+
coeff = S.One
|
143 |
+
else:
|
144 |
+
coeff = S.NegativeOne
|
145 |
+
|
146 |
+
coeff *= prod(range(3, 2*k, 2))
|
147 |
+
|
148 |
+
if arg.is_positive:
|
149 |
+
return coeff*sqrt(pi) / 2**n
|
150 |
+
else:
|
151 |
+
return 2**n*sqrt(pi) / coeff
|
152 |
+
|
153 |
+
def _eval_expand_func(self, **hints):
|
154 |
+
arg = self.args[0]
|
155 |
+
if arg.is_Rational:
|
156 |
+
if abs(arg.p) > arg.q:
|
157 |
+
x = Dummy('x')
|
158 |
+
n = arg.p // arg.q
|
159 |
+
p = arg.p - n*arg.q
|
160 |
+
return self.func(x + n)._eval_expand_func().subs(x, Rational(p, arg.q))
|
161 |
+
|
162 |
+
if arg.is_Add:
|
163 |
+
coeff, tail = arg.as_coeff_add()
|
164 |
+
if coeff and coeff.q != 1:
|
165 |
+
intpart = floor(coeff)
|
166 |
+
tail = (coeff - intpart,) + tail
|
167 |
+
coeff = intpart
|
168 |
+
tail = arg._new_rawargs(*tail, reeval=False)
|
169 |
+
return self.func(tail)*RisingFactorial(tail, coeff)
|
170 |
+
|
171 |
+
return self.func(*self.args)
|
172 |
+
|
173 |
+
def _eval_conjugate(self):
|
174 |
+
return self.func(self.args[0].conjugate())
|
175 |
+
|
176 |
+
def _eval_is_real(self):
|
177 |
+
x = self.args[0]
|
178 |
+
if x.is_nonpositive and x.is_integer:
|
179 |
+
return False
|
180 |
+
if intlike(x) and x <= 0:
|
181 |
+
return False
|
182 |
+
if x.is_positive or x.is_noninteger:
|
183 |
+
return True
|
184 |
+
|
185 |
+
def _eval_is_positive(self):
|
186 |
+
x = self.args[0]
|
187 |
+
if x.is_positive:
|
188 |
+
return True
|
189 |
+
elif x.is_noninteger:
|
190 |
+
return floor(x).is_even
|
191 |
+
|
192 |
+
def _eval_rewrite_as_tractable(self, z, limitvar=None, **kwargs):
|
193 |
+
return exp(loggamma(z))
|
194 |
+
|
195 |
+
def _eval_rewrite_as_factorial(self, z, **kwargs):
|
196 |
+
return factorial(z - 1)
|
197 |
+
|
198 |
+
def _eval_nseries(self, x, n, logx, cdir=0):
|
199 |
+
x0 = self.args[0].limit(x, 0)
|
200 |
+
if not (x0.is_Integer and x0 <= 0):
|
201 |
+
return super()._eval_nseries(x, n, logx)
|
202 |
+
t = self.args[0] - x0
|
203 |
+
return (self.func(t + 1)/rf(self.args[0], -x0 + 1))._eval_nseries(x, n, logx)
|
204 |
+
|
205 |
+
def _eval_as_leading_term(self, x, logx=None, cdir=0):
|
206 |
+
arg = self.args[0]
|
207 |
+
x0 = arg.subs(x, 0)
|
208 |
+
|
209 |
+
if x0.is_integer and x0.is_nonpositive:
|
210 |
+
n = -x0
|
211 |
+
res = S.NegativeOne**n/self.func(n + 1)
|
212 |
+
return res/(arg + n).as_leading_term(x)
|
213 |
+
elif not x0.is_infinite:
|
214 |
+
return self.func(x0)
|
215 |
+
raise PoleError()
|
216 |
+
|
217 |
+
|
218 |
+
###############################################################################
|
219 |
+
################## LOWER and UPPER INCOMPLETE GAMMA FUNCTIONS #################
|
220 |
+
###############################################################################
|
221 |
+
|
222 |
+
class lowergamma(Function):
|
223 |
+
r"""
|
224 |
+
The lower incomplete gamma function.
|
225 |
+
|
226 |
+
Explanation
|
227 |
+
===========
|
228 |
+
|
229 |
+
It can be defined as the meromorphic continuation of
|
230 |
+
|
231 |
+
.. math::
|
232 |
+
\gamma(s, x) := \int_0^x t^{s-1} e^{-t} \mathrm{d}t = \Gamma(s) - \Gamma(s, x).
|
233 |
+
|
234 |
+
This can be shown to be the same as
|
235 |
+
|
236 |
+
.. math::
|
237 |
+
\gamma(s, x) = \frac{x^s}{s} {}_1F_1\left({s \atop s+1} \middle| -x\right),
|
238 |
+
|
239 |
+
where ${}_1F_1$ is the (confluent) hypergeometric function.
|
240 |
+
|
241 |
+
Examples
|
242 |
+
========
|
243 |
+
|
244 |
+
>>> from sympy import lowergamma, S
|
245 |
+
>>> from sympy.abc import s, x
|
246 |
+
>>> lowergamma(s, x)
|
247 |
+
lowergamma(s, x)
|
248 |
+
>>> lowergamma(3, x)
|
249 |
+
-2*(x**2/2 + x + 1)*exp(-x) + 2
|
250 |
+
>>> lowergamma(-S(1)/2, x)
|
251 |
+
-2*sqrt(pi)*erf(sqrt(x)) - 2*exp(-x)/sqrt(x)
|
252 |
+
|
253 |
+
See Also
|
254 |
+
========
|
255 |
+
|
256 |
+
gamma: Gamma function.
|
257 |
+
uppergamma: Upper incomplete gamma function.
|
258 |
+
polygamma: Polygamma function.
|
259 |
+
loggamma: Log Gamma function.
|
260 |
+
digamma: Digamma function.
|
261 |
+
trigamma: Trigamma function.
|
262 |
+
beta: Euler Beta function.
|
263 |
+
|
264 |
+
References
|
265 |
+
==========
|
266 |
+
|
267 |
+
.. [1] https://en.wikipedia.org/wiki/Incomplete_gamma_function#Lower_incomplete_gamma_function
|
268 |
+
.. [2] Abramowitz, Milton; Stegun, Irene A., eds. (1965), Chapter 6,
|
269 |
+
Section 5, Handbook of Mathematical Functions with Formulas, Graphs,
|
270 |
+
and Mathematical Tables
|
271 |
+
.. [3] https://dlmf.nist.gov/8
|
272 |
+
.. [4] https://functions.wolfram.com/GammaBetaErf/Gamma2/
|
273 |
+
.. [5] https://functions.wolfram.com/GammaBetaErf/Gamma3/
|
274 |
+
|
275 |
+
"""
|
276 |
+
|
277 |
+
|
278 |
+
def fdiff(self, argindex=2):
|
279 |
+
from sympy.functions.special.hyper import meijerg
|
280 |
+
if argindex == 2:
|
281 |
+
a, z = self.args
|
282 |
+
return exp(-unpolarify(z))*z**(a - 1)
|
283 |
+
elif argindex == 1:
|
284 |
+
a, z = self.args
|
285 |
+
return gamma(a)*digamma(a) - log(z)*uppergamma(a, z) \
|
286 |
+
- meijerg([], [1, 1], [0, 0, a], [], z)
|
287 |
+
|
288 |
+
else:
|
289 |
+
raise ArgumentIndexError(self, argindex)
|
290 |
+
|
291 |
+
@classmethod
|
292 |
+
def eval(cls, a, x):
|
293 |
+
# For lack of a better place, we use this one to extract branching
|
294 |
+
# information. The following can be
|
295 |
+
# found in the literature (c/f references given above), albeit scattered:
|
296 |
+
# 1) For fixed x != 0, lowergamma(s, x) is an entire function of s
|
297 |
+
# 2) For fixed positive integers s, lowergamma(s, x) is an entire
|
298 |
+
# function of x.
|
299 |
+
# 3) For fixed non-positive integers s,
|
300 |
+
# lowergamma(s, exp(I*2*pi*n)*x) =
|
301 |
+
# 2*pi*I*n*(-1)**(-s)/factorial(-s) + lowergamma(s, x)
|
302 |
+
# (this follows from lowergamma(s, x).diff(x) = x**(s-1)*exp(-x)).
|
303 |
+
# 4) For fixed non-integral s,
|
304 |
+
# lowergamma(s, x) = x**s*gamma(s)*lowergamma_unbranched(s, x),
|
305 |
+
# where lowergamma_unbranched(s, x) is an entire function (in fact
|
306 |
+
# of both s and x), i.e.
|
307 |
+
# lowergamma(s, exp(2*I*pi*n)*x) = exp(2*pi*I*n*a)*lowergamma(a, x)
|
308 |
+
if x is S.Zero:
|
309 |
+
return S.Zero
|
310 |
+
nx, n = x.extract_branch_factor()
|
311 |
+
if a.is_integer and a.is_positive:
|
312 |
+
nx = unpolarify(x)
|
313 |
+
if nx != x:
|
314 |
+
return lowergamma(a, nx)
|
315 |
+
elif a.is_integer and a.is_nonpositive:
|
316 |
+
if n != 0:
|
317 |
+
return 2*pi*I*n*S.NegativeOne**(-a)/factorial(-a) + lowergamma(a, nx)
|
318 |
+
elif n != 0:
|
319 |
+
return exp(2*pi*I*n*a)*lowergamma(a, nx)
|
320 |
+
|
321 |
+
# Special values.
|
322 |
+
if a.is_Number:
|
323 |
+
if a is S.One:
|
324 |
+
return S.One - exp(-x)
|
325 |
+
elif a is S.Half:
|
326 |
+
return sqrt(pi)*erf(sqrt(x))
|
327 |
+
elif a.is_Integer or (2*a).is_Integer:
|
328 |
+
b = a - 1
|
329 |
+
if b.is_positive:
|
330 |
+
if a.is_integer:
|
331 |
+
return factorial(b) - exp(-x) * factorial(b) * Add(*[x ** k / factorial(k) for k in range(a)])
|
332 |
+
else:
|
333 |
+
return gamma(a)*(lowergamma(S.Half, x)/sqrt(pi) - exp(-x)*Add(*[x**(k - S.Half)/gamma(S.Half + k) for k in range(1, a + S.Half)]))
|
334 |
+
|
335 |
+
if not a.is_Integer:
|
336 |
+
return S.NegativeOne**(S.Half - a)*pi*erf(sqrt(x))/gamma(1 - a) + exp(-x)*Add(*[x**(k + a - 1)*gamma(a)/gamma(a + k) for k in range(1, Rational(3, 2) - a)])
|
337 |
+
|
338 |
+
if x.is_zero:
|
339 |
+
return S.Zero
|
340 |
+
|
341 |
+
def _eval_evalf(self, prec):
|
342 |
+
if all(x.is_number for x in self.args):
|
343 |
+
a = self.args[0]._to_mpmath(prec)
|
344 |
+
z = self.args[1]._to_mpmath(prec)
|
345 |
+
with workprec(prec):
|
346 |
+
res = mp.gammainc(a, 0, z)
|
347 |
+
return Expr._from_mpmath(res, prec)
|
348 |
+
else:
|
349 |
+
return self
|
350 |
+
|
351 |
+
def _eval_conjugate(self):
|
352 |
+
x = self.args[1]
|
353 |
+
if x not in (S.Zero, S.NegativeInfinity):
|
354 |
+
return self.func(self.args[0].conjugate(), x.conjugate())
|
355 |
+
|
356 |
+
def _eval_is_meromorphic(self, x, a):
|
357 |
+
# By https://en.wikipedia.org/wiki/Incomplete_gamma_function#Holomorphic_extension,
|
358 |
+
# lowergamma(s, z) = z**s*gamma(s)*gammastar(s, z),
|
359 |
+
# where gammastar(s, z) is holomorphic for all s and z.
|
360 |
+
# Hence the singularities of lowergamma are z = 0 (branch
|
361 |
+
# point) and nonpositive integer values of s (poles of gamma(s)).
|
362 |
+
s, z = self.args
|
363 |
+
args_merom = fuzzy_and([z._eval_is_meromorphic(x, a),
|
364 |
+
s._eval_is_meromorphic(x, a)])
|
365 |
+
if not args_merom:
|
366 |
+
return args_merom
|
367 |
+
z0 = z.subs(x, a)
|
368 |
+
if s.is_integer:
|
369 |
+
return fuzzy_and([s.is_positive, z0.is_finite])
|
370 |
+
s0 = s.subs(x, a)
|
371 |
+
return fuzzy_and([s0.is_finite, z0.is_finite, fuzzy_not(z0.is_zero)])
|
372 |
+
|
373 |
+
def _eval_aseries(self, n, args0, x, logx):
|
374 |
+
from sympy.series.order import O
|
375 |
+
s, z = self.args
|
376 |
+
if args0[0] is oo and not z.has(x):
|
377 |
+
coeff = z**s*exp(-z)
|
378 |
+
sum_expr = sum(z**k/rf(s, k + 1) for k in range(n - 1))
|
379 |
+
o = O(z**s*s**(-n))
|
380 |
+
return coeff*sum_expr + o
|
381 |
+
return super()._eval_aseries(n, args0, x, logx)
|
382 |
+
|
383 |
+
def _eval_rewrite_as_uppergamma(self, s, x, **kwargs):
|
384 |
+
return gamma(s) - uppergamma(s, x)
|
385 |
+
|
386 |
+
def _eval_rewrite_as_expint(self, s, x, **kwargs):
|
387 |
+
from sympy.functions.special.error_functions import expint
|
388 |
+
if s.is_integer and s.is_nonpositive:
|
389 |
+
return self
|
390 |
+
return self.rewrite(uppergamma).rewrite(expint)
|
391 |
+
|
392 |
+
def _eval_is_zero(self):
|
393 |
+
x = self.args[1]
|
394 |
+
if x.is_zero:
|
395 |
+
return True
|
396 |
+
|
397 |
+
|
398 |
+
class uppergamma(Function):
|
399 |
+
r"""
|
400 |
+
The upper incomplete gamma function.
|
401 |
+
|
402 |
+
Explanation
|
403 |
+
===========
|
404 |
+
|
405 |
+
It can be defined as the meromorphic continuation of
|
406 |
+
|
407 |
+
.. math::
|
408 |
+
\Gamma(s, x) := \int_x^\infty t^{s-1} e^{-t} \mathrm{d}t = \Gamma(s) - \gamma(s, x).
|
409 |
+
|
410 |
+
where $\gamma(s, x)$ is the lower incomplete gamma function,
|
411 |
+
:class:`lowergamma`. This can be shown to be the same as
|
412 |
+
|
413 |
+
.. math::
|
414 |
+
\Gamma(s, x) = \Gamma(s) - \frac{x^s}{s} {}_1F_1\left({s \atop s+1} \middle| -x\right),
|
415 |
+
|
416 |
+
where ${}_1F_1$ is the (confluent) hypergeometric function.
|
417 |
+
|
418 |
+
The upper incomplete gamma function is also essentially equivalent to the
|
419 |
+
generalized exponential integral:
|
420 |
+
|
421 |
+
.. math::
|
422 |
+
\operatorname{E}_{n}(x) = \int_{1}^{\infty}{\frac{e^{-xt}}{t^n} \, dt} = x^{n-1}\Gamma(1-n,x).
|
423 |
+
|
424 |
+
Examples
|
425 |
+
========
|
426 |
+
|
427 |
+
>>> from sympy import uppergamma, S
|
428 |
+
>>> from sympy.abc import s, x
|
429 |
+
>>> uppergamma(s, x)
|
430 |
+
uppergamma(s, x)
|
431 |
+
>>> uppergamma(3, x)
|
432 |
+
2*(x**2/2 + x + 1)*exp(-x)
|
433 |
+
>>> uppergamma(-S(1)/2, x)
|
434 |
+
-2*sqrt(pi)*erfc(sqrt(x)) + 2*exp(-x)/sqrt(x)
|
435 |
+
>>> uppergamma(-2, x)
|
436 |
+
expint(3, x)/x**2
|
437 |
+
|
438 |
+
See Also
|
439 |
+
========
|
440 |
+
|
441 |
+
gamma: Gamma function.
|
442 |
+
lowergamma: Lower incomplete gamma function.
|
443 |
+
polygamma: Polygamma function.
|
444 |
+
loggamma: Log Gamma function.
|
445 |
+
digamma: Digamma function.
|
446 |
+
trigamma: Trigamma function.
|
447 |
+
beta: Euler Beta function.
|
448 |
+
|
449 |
+
References
|
450 |
+
==========
|
451 |
+
|
452 |
+
.. [1] https://en.wikipedia.org/wiki/Incomplete_gamma_function#Upper_incomplete_gamma_function
|
453 |
+
.. [2] Abramowitz, Milton; Stegun, Irene A., eds. (1965), Chapter 6,
|
454 |
+
Section 5, Handbook of Mathematical Functions with Formulas, Graphs,
|
455 |
+
and Mathematical Tables
|
456 |
+
.. [3] https://dlmf.nist.gov/8
|
457 |
+
.. [4] https://functions.wolfram.com/GammaBetaErf/Gamma2/
|
458 |
+
.. [5] https://functions.wolfram.com/GammaBetaErf/Gamma3/
|
459 |
+
.. [6] https://en.wikipedia.org/wiki/Exponential_integral#Relation_with_other_functions
|
460 |
+
|
461 |
+
"""
|
462 |
+
|
463 |
+
|
464 |
+
def fdiff(self, argindex=2):
|
465 |
+
from sympy.functions.special.hyper import meijerg
|
466 |
+
if argindex == 2:
|
467 |
+
a, z = self.args
|
468 |
+
return -exp(-unpolarify(z))*z**(a - 1)
|
469 |
+
elif argindex == 1:
|
470 |
+
a, z = self.args
|
471 |
+
return uppergamma(a, z)*log(z) + meijerg([], [1, 1], [0, 0, a], [], z)
|
472 |
+
else:
|
473 |
+
raise ArgumentIndexError(self, argindex)
|
474 |
+
|
475 |
+
def _eval_evalf(self, prec):
|
476 |
+
if all(x.is_number for x in self.args):
|
477 |
+
a = self.args[0]._to_mpmath(prec)
|
478 |
+
z = self.args[1]._to_mpmath(prec)
|
479 |
+
with workprec(prec):
|
480 |
+
res = mp.gammainc(a, z, mp.inf)
|
481 |
+
return Expr._from_mpmath(res, prec)
|
482 |
+
return self
|
483 |
+
|
484 |
+
@classmethod
|
485 |
+
def eval(cls, a, z):
|
486 |
+
from sympy.functions.special.error_functions import expint
|
487 |
+
if z.is_Number:
|
488 |
+
if z is S.NaN:
|
489 |
+
return S.NaN
|
490 |
+
elif z is oo:
|
491 |
+
return S.Zero
|
492 |
+
elif z.is_zero:
|
493 |
+
if re(a).is_positive:
|
494 |
+
return gamma(a)
|
495 |
+
|
496 |
+
# We extract branching information here. C/f lowergamma.
|
497 |
+
nx, n = z.extract_branch_factor()
|
498 |
+
if a.is_integer and a.is_positive:
|
499 |
+
nx = unpolarify(z)
|
500 |
+
if z != nx:
|
501 |
+
return uppergamma(a, nx)
|
502 |
+
elif a.is_integer and a.is_nonpositive:
|
503 |
+
if n != 0:
|
504 |
+
return -2*pi*I*n*S.NegativeOne**(-a)/factorial(-a) + uppergamma(a, nx)
|
505 |
+
elif n != 0:
|
506 |
+
return gamma(a)*(1 - exp(2*pi*I*n*a)) + exp(2*pi*I*n*a)*uppergamma(a, nx)
|
507 |
+
|
508 |
+
# Special values.
|
509 |
+
if a.is_Number:
|
510 |
+
if a is S.Zero and z.is_positive:
|
511 |
+
return -Ei(-z)
|
512 |
+
elif a is S.One:
|
513 |
+
return exp(-z)
|
514 |
+
elif a is S.Half:
|
515 |
+
return sqrt(pi)*erfc(sqrt(z))
|
516 |
+
elif a.is_Integer or (2*a).is_Integer:
|
517 |
+
b = a - 1
|
518 |
+
if b.is_positive:
|
519 |
+
if a.is_integer:
|
520 |
+
return exp(-z) * factorial(b) * Add(*[z**k / factorial(k)
|
521 |
+
for k in range(a)])
|
522 |
+
else:
|
523 |
+
return (gamma(a) * erfc(sqrt(z)) +
|
524 |
+
S.NegativeOne**(a - S(3)/2) * exp(-z) * sqrt(z)
|
525 |
+
* Add(*[gamma(-S.Half - k) * (-z)**k / gamma(1-a)
|
526 |
+
for k in range(a - S.Half)]))
|
527 |
+
elif b.is_Integer:
|
528 |
+
return expint(-b, z)*unpolarify(z)**(b + 1)
|
529 |
+
|
530 |
+
if not a.is_Integer:
|
531 |
+
return (S.NegativeOne**(S.Half - a) * pi*erfc(sqrt(z))/gamma(1-a)
|
532 |
+
- z**a * exp(-z) * Add(*[z**k * gamma(a) / gamma(a+k+1)
|
533 |
+
for k in range(S.Half - a)]))
|
534 |
+
|
535 |
+
if a.is_zero and z.is_positive:
|
536 |
+
return -Ei(-z)
|
537 |
+
|
538 |
+
if z.is_zero and re(a).is_positive:
|
539 |
+
return gamma(a)
|
540 |
+
|
541 |
+
def _eval_conjugate(self):
|
542 |
+
z = self.args[1]
|
543 |
+
if z not in (S.Zero, S.NegativeInfinity):
|
544 |
+
return self.func(self.args[0].conjugate(), z.conjugate())
|
545 |
+
|
546 |
+
def _eval_is_meromorphic(self, x, a):
|
547 |
+
return lowergamma._eval_is_meromorphic(self, x, a)
|
548 |
+
|
549 |
+
def _eval_rewrite_as_lowergamma(self, s, x, **kwargs):
|
550 |
+
return gamma(s) - lowergamma(s, x)
|
551 |
+
|
552 |
+
def _eval_rewrite_as_tractable(self, s, x, **kwargs):
|
553 |
+
return exp(loggamma(s)) - lowergamma(s, x)
|
554 |
+
|
555 |
+
def _eval_rewrite_as_expint(self, s, x, **kwargs):
|
556 |
+
from sympy.functions.special.error_functions import expint
|
557 |
+
return expint(1 - s, x)*x**s
|
558 |
+
|
559 |
+
|
560 |
+
###############################################################################
|
561 |
+
###################### POLYGAMMA and LOGGAMMA FUNCTIONS #######################
|
562 |
+
###############################################################################
|
563 |
+
|
564 |
+
class polygamma(Function):
|
565 |
+
r"""
|
566 |
+
The function ``polygamma(n, z)`` returns ``log(gamma(z)).diff(n + 1)``.
|
567 |
+
|
568 |
+
Explanation
|
569 |
+
===========
|
570 |
+
|
571 |
+
It is a meromorphic function on $\mathbb{C}$ and defined as the $(n+1)$-th
|
572 |
+
derivative of the logarithm of the gamma function:
|
573 |
+
|
574 |
+
.. math::
|
575 |
+
\psi^{(n)} (z) := \frac{\mathrm{d}^{n+1}}{\mathrm{d} z^{n+1}} \log\Gamma(z).
|
576 |
+
|
577 |
+
For `n` not a nonnegative integer the generalization by Espinosa and Moll [5]_
|
578 |
+
is used:
|
579 |
+
|
580 |
+
.. math:: \psi(s,z) = \frac{\zeta'(s+1, z) + (\gamma + \psi(-s)) \zeta(s+1, z)}
|
581 |
+
{\Gamma(-s)}
|
582 |
+
|
583 |
+
Examples
|
584 |
+
========
|
585 |
+
|
586 |
+
Several special values are known:
|
587 |
+
|
588 |
+
>>> from sympy import S, polygamma
|
589 |
+
>>> polygamma(0, 1)
|
590 |
+
-EulerGamma
|
591 |
+
>>> polygamma(0, 1/S(2))
|
592 |
+
-2*log(2) - EulerGamma
|
593 |
+
>>> polygamma(0, 1/S(3))
|
594 |
+
-log(3) - sqrt(3)*pi/6 - EulerGamma - log(sqrt(3))
|
595 |
+
>>> polygamma(0, 1/S(4))
|
596 |
+
-pi/2 - log(4) - log(2) - EulerGamma
|
597 |
+
>>> polygamma(0, 2)
|
598 |
+
1 - EulerGamma
|
599 |
+
>>> polygamma(0, 23)
|
600 |
+
19093197/5173168 - EulerGamma
|
601 |
+
|
602 |
+
>>> from sympy import oo, I
|
603 |
+
>>> polygamma(0, oo)
|
604 |
+
oo
|
605 |
+
>>> polygamma(0, -oo)
|
606 |
+
oo
|
607 |
+
>>> polygamma(0, I*oo)
|
608 |
+
oo
|
609 |
+
>>> polygamma(0, -I*oo)
|
610 |
+
oo
|
611 |
+
|
612 |
+
Differentiation with respect to $x$ is supported:
|
613 |
+
|
614 |
+
>>> from sympy import Symbol, diff
|
615 |
+
>>> x = Symbol("x")
|
616 |
+
>>> diff(polygamma(0, x), x)
|
617 |
+
polygamma(1, x)
|
618 |
+
>>> diff(polygamma(0, x), x, 2)
|
619 |
+
polygamma(2, x)
|
620 |
+
>>> diff(polygamma(0, x), x, 3)
|
621 |
+
polygamma(3, x)
|
622 |
+
>>> diff(polygamma(1, x), x)
|
623 |
+
polygamma(2, x)
|
624 |
+
>>> diff(polygamma(1, x), x, 2)
|
625 |
+
polygamma(3, x)
|
626 |
+
>>> diff(polygamma(2, x), x)
|
627 |
+
polygamma(3, x)
|
628 |
+
>>> diff(polygamma(2, x), x, 2)
|
629 |
+
polygamma(4, x)
|
630 |
+
|
631 |
+
>>> n = Symbol("n")
|
632 |
+
>>> diff(polygamma(n, x), x)
|
633 |
+
polygamma(n + 1, x)
|
634 |
+
>>> diff(polygamma(n, x), x, 2)
|
635 |
+
polygamma(n + 2, x)
|
636 |
+
|
637 |
+
We can rewrite ``polygamma`` functions in terms of harmonic numbers:
|
638 |
+
|
639 |
+
>>> from sympy import harmonic
|
640 |
+
>>> polygamma(0, x).rewrite(harmonic)
|
641 |
+
harmonic(x - 1) - EulerGamma
|
642 |
+
>>> polygamma(2, x).rewrite(harmonic)
|
643 |
+
2*harmonic(x - 1, 3) - 2*zeta(3)
|
644 |
+
>>> ni = Symbol("n", integer=True)
|
645 |
+
>>> polygamma(ni, x).rewrite(harmonic)
|
646 |
+
(-1)**(n + 1)*(-harmonic(x - 1, n + 1) + zeta(n + 1))*factorial(n)
|
647 |
+
|
648 |
+
See Also
|
649 |
+
========
|
650 |
+
|
651 |
+
gamma: Gamma function.
|
652 |
+
lowergamma: Lower incomplete gamma function.
|
653 |
+
uppergamma: Upper incomplete gamma function.
|
654 |
+
loggamma: Log Gamma function.
|
655 |
+
digamma: Digamma function.
|
656 |
+
trigamma: Trigamma function.
|
657 |
+
beta: Euler Beta function.
|
658 |
+
|
659 |
+
References
|
660 |
+
==========
|
661 |
+
|
662 |
+
.. [1] https://en.wikipedia.org/wiki/Polygamma_function
|
663 |
+
.. [2] https://mathworld.wolfram.com/PolygammaFunction.html
|
664 |
+
.. [3] https://functions.wolfram.com/GammaBetaErf/PolyGamma/
|
665 |
+
.. [4] https://functions.wolfram.com/GammaBetaErf/PolyGamma2/
|
666 |
+
.. [5] O. Espinosa and V. Moll, "A generalized polygamma function",
|
667 |
+
*Integral Transforms and Special Functions* (2004), 101-115.
|
668 |
+
|
669 |
+
"""
|
670 |
+
|
671 |
+
@classmethod
|
672 |
+
def eval(cls, n, z):
|
673 |
+
if n is S.NaN or z is S.NaN:
|
674 |
+
return S.NaN
|
675 |
+
elif z is oo:
|
676 |
+
return oo if n.is_zero else S.Zero
|
677 |
+
elif z.is_Integer and z.is_nonpositive:
|
678 |
+
return S.ComplexInfinity
|
679 |
+
elif n is S.NegativeOne:
|
680 |
+
return loggamma(z) - log(2*pi) / 2
|
681 |
+
elif n.is_zero:
|
682 |
+
if z is -oo or z.extract_multiplicatively(I) in (oo, -oo):
|
683 |
+
return oo
|
684 |
+
elif z.is_Integer:
|
685 |
+
return harmonic(z-1) - S.EulerGamma
|
686 |
+
elif z.is_Rational:
|
687 |
+
# TODO n == 1 also can do some rational z
|
688 |
+
p, q = z.as_numer_denom()
|
689 |
+
# only expand for small denominators to avoid creating long expressions
|
690 |
+
if q <= 6:
|
691 |
+
return expand_func(polygamma(S.Zero, z, evaluate=False))
|
692 |
+
elif n.is_integer and n.is_nonnegative:
|
693 |
+
nz = unpolarify(z)
|
694 |
+
if z != nz:
|
695 |
+
return polygamma(n, nz)
|
696 |
+
if z.is_Integer:
|
697 |
+
return S.NegativeOne**(n+1) * factorial(n) * zeta(n+1, z)
|
698 |
+
elif z is S.Half:
|
699 |
+
return S.NegativeOne**(n+1) * factorial(n) * (2**(n+1)-1) * zeta(n+1)
|
700 |
+
|
701 |
+
def _eval_is_real(self):
|
702 |
+
if self.args[0].is_positive and self.args[1].is_positive:
|
703 |
+
return True
|
704 |
+
|
705 |
+
def _eval_is_complex(self):
|
706 |
+
z = self.args[1]
|
707 |
+
is_negative_integer = fuzzy_and([z.is_negative, z.is_integer])
|
708 |
+
return fuzzy_and([z.is_complex, fuzzy_not(is_negative_integer)])
|
709 |
+
|
710 |
+
def _eval_is_positive(self):
|
711 |
+
n, z = self.args
|
712 |
+
if n.is_positive:
|
713 |
+
if n.is_odd and z.is_real:
|
714 |
+
return True
|
715 |
+
if n.is_even and z.is_positive:
|
716 |
+
return False
|
717 |
+
|
718 |
+
def _eval_is_negative(self):
|
719 |
+
n, z = self.args
|
720 |
+
if n.is_positive:
|
721 |
+
if n.is_even and z.is_positive:
|
722 |
+
return True
|
723 |
+
if n.is_odd and z.is_real:
|
724 |
+
return False
|
725 |
+
|
726 |
+
def _eval_expand_func(self, **hints):
|
727 |
+
n, z = self.args
|
728 |
+
|
729 |
+
if n.is_Integer and n.is_nonnegative:
|
730 |
+
if z.is_Add:
|
731 |
+
coeff = z.args[0]
|
732 |
+
if coeff.is_Integer:
|
733 |
+
e = -(n + 1)
|
734 |
+
if coeff > 0:
|
735 |
+
tail = Add(*[Pow(
|
736 |
+
z - i, e) for i in range(1, int(coeff) + 1)])
|
737 |
+
else:
|
738 |
+
tail = -Add(*[Pow(
|
739 |
+
z + i, e) for i in range(int(-coeff))])
|
740 |
+
return polygamma(n, z - coeff) + S.NegativeOne**n*factorial(n)*tail
|
741 |
+
|
742 |
+
elif z.is_Mul:
|
743 |
+
coeff, z = z.as_two_terms()
|
744 |
+
if coeff.is_Integer and coeff.is_positive:
|
745 |
+
tail = [polygamma(n, z + Rational(
|
746 |
+
i, coeff)) for i in range(int(coeff))]
|
747 |
+
if n == 0:
|
748 |
+
return Add(*tail)/coeff + log(coeff)
|
749 |
+
else:
|
750 |
+
return Add(*tail)/coeff**(n + 1)
|
751 |
+
z *= coeff
|
752 |
+
|
753 |
+
if n == 0 and z.is_Rational:
|
754 |
+
p, q = z.as_numer_denom()
|
755 |
+
|
756 |
+
# Reference:
|
757 |
+
# Values of the polygamma functions at rational arguments, J. Choi, 2007
|
758 |
+
part_1 = -S.EulerGamma - pi * cot(p * pi / q) / 2 - log(q) + Add(
|
759 |
+
*[cos(2 * k * pi * p / q) * log(2 * sin(k * pi / q)) for k in range(1, q)])
|
760 |
+
|
761 |
+
if z > 0:
|
762 |
+
n = floor(z)
|
763 |
+
z0 = z - n
|
764 |
+
return part_1 + Add(*[1 / (z0 + k) for k in range(n)])
|
765 |
+
elif z < 0:
|
766 |
+
n = floor(1 - z)
|
767 |
+
z0 = z + n
|
768 |
+
return part_1 - Add(*[1 / (z0 - 1 - k) for k in range(n)])
|
769 |
+
|
770 |
+
if n == -1:
|
771 |
+
return loggamma(z) - log(2*pi) / 2
|
772 |
+
if n.is_integer is False or n.is_nonnegative is False:
|
773 |
+
s = Dummy("s")
|
774 |
+
dzt = zeta(s, z).diff(s).subs(s, n+1)
|
775 |
+
return (dzt + (S.EulerGamma + digamma(-n)) * zeta(n+1, z)) / gamma(-n)
|
776 |
+
|
777 |
+
return polygamma(n, z)
|
778 |
+
|
779 |
+
def _eval_rewrite_as_zeta(self, n, z, **kwargs):
|
780 |
+
if n.is_integer and n.is_positive:
|
781 |
+
return S.NegativeOne**(n + 1)*factorial(n)*zeta(n + 1, z)
|
782 |
+
|
783 |
+
def _eval_rewrite_as_harmonic(self, n, z, **kwargs):
|
784 |
+
if n.is_integer:
|
785 |
+
if n.is_zero:
|
786 |
+
return harmonic(z - 1) - S.EulerGamma
|
787 |
+
else:
|
788 |
+
return S.NegativeOne**(n+1) * factorial(n) * (zeta(n+1) - harmonic(z-1, n+1))
|
789 |
+
|
790 |
+
def _eval_as_leading_term(self, x, logx=None, cdir=0):
|
791 |
+
from sympy.series.order import Order
|
792 |
+
n, z = [a.as_leading_term(x) for a in self.args]
|
793 |
+
o = Order(z, x)
|
794 |
+
if n == 0 and o.contains(1/x):
|
795 |
+
logx = log(x) if logx is None else logx
|
796 |
+
return o.getn() * logx
|
797 |
+
else:
|
798 |
+
return self.func(n, z)
|
799 |
+
|
800 |
+
def fdiff(self, argindex=2):
|
801 |
+
if argindex == 2:
|
802 |
+
n, z = self.args[:2]
|
803 |
+
return polygamma(n + 1, z)
|
804 |
+
else:
|
805 |
+
raise ArgumentIndexError(self, argindex)
|
806 |
+
|
807 |
+
def _eval_aseries(self, n, args0, x, logx):
|
808 |
+
from sympy.series.order import Order
|
809 |
+
if args0[1] != oo or not \
|
810 |
+
(self.args[0].is_Integer and self.args[0].is_nonnegative):
|
811 |
+
return super()._eval_aseries(n, args0, x, logx)
|
812 |
+
z = self.args[1]
|
813 |
+
N = self.args[0]
|
814 |
+
|
815 |
+
if N == 0:
|
816 |
+
# digamma function series
|
817 |
+
# Abramowitz & Stegun, p. 259, 6.3.18
|
818 |
+
r = log(z) - 1/(2*z)
|
819 |
+
o = None
|
820 |
+
if n < 2:
|
821 |
+
o = Order(1/z, x)
|
822 |
+
else:
|
823 |
+
m = ceiling((n + 1)//2)
|
824 |
+
l = [bernoulli(2*k) / (2*k*z**(2*k)) for k in range(1, m)]
|
825 |
+
r -= Add(*l)
|
826 |
+
o = Order(1/z**n, x)
|
827 |
+
return r._eval_nseries(x, n, logx) + o
|
828 |
+
else:
|
829 |
+
# proper polygamma function
|
830 |
+
# Abramowitz & Stegun, p. 260, 6.4.10
|
831 |
+
# We return terms to order higher than O(x**n) on purpose
|
832 |
+
# -- otherwise we would not be able to return any terms for
|
833 |
+
# quite a long time!
|
834 |
+
fac = gamma(N)
|
835 |
+
e0 = fac + N*fac/(2*z)
|
836 |
+
m = ceiling((n + 1)//2)
|
837 |
+
for k in range(1, m):
|
838 |
+
fac = fac*(2*k + N - 1)*(2*k + N - 2) / ((2*k)*(2*k - 1))
|
839 |
+
e0 += bernoulli(2*k)*fac/z**(2*k)
|
840 |
+
o = Order(1/z**(2*m), x)
|
841 |
+
if n == 0:
|
842 |
+
o = Order(1/z, x)
|
843 |
+
elif n == 1:
|
844 |
+
o = Order(1/z**2, x)
|
845 |
+
r = e0._eval_nseries(z, n, logx) + o
|
846 |
+
return (-1 * (-1/z)**N * r)._eval_nseries(x, n, logx)
|
847 |
+
|
848 |
+
def _eval_evalf(self, prec):
|
849 |
+
if not all(i.is_number for i in self.args):
|
850 |
+
return
|
851 |
+
s = self.args[0]._to_mpmath(prec+12)
|
852 |
+
z = self.args[1]._to_mpmath(prec+12)
|
853 |
+
if mp.isint(z) and z <= 0:
|
854 |
+
return S.ComplexInfinity
|
855 |
+
with workprec(prec+12):
|
856 |
+
if mp.isint(s) and s >= 0:
|
857 |
+
res = mp.polygamma(s, z)
|
858 |
+
else:
|
859 |
+
zt = mp.zeta(s+1, z)
|
860 |
+
dzt = mp.zeta(s+1, z, 1)
|
861 |
+
res = (dzt + (mp.euler + mp.digamma(-s)) * zt) * mp.rgamma(-s)
|
862 |
+
return Expr._from_mpmath(res, prec)
|
863 |
+
|
864 |
+
|
865 |
+
class loggamma(Function):
|
866 |
+
r"""
|
867 |
+
The ``loggamma`` function implements the logarithm of the
|
868 |
+
gamma function (i.e., $\log\Gamma(x)$).
|
869 |
+
|
870 |
+
Examples
|
871 |
+
========
|
872 |
+
|
873 |
+
Several special values are known. For numerical integral
|
874 |
+
arguments we have:
|
875 |
+
|
876 |
+
>>> from sympy import loggamma
|
877 |
+
>>> loggamma(-2)
|
878 |
+
oo
|
879 |
+
>>> loggamma(0)
|
880 |
+
oo
|
881 |
+
>>> loggamma(1)
|
882 |
+
0
|
883 |
+
>>> loggamma(2)
|
884 |
+
0
|
885 |
+
>>> loggamma(3)
|
886 |
+
log(2)
|
887 |
+
|
888 |
+
And for symbolic values:
|
889 |
+
|
890 |
+
>>> from sympy import Symbol
|
891 |
+
>>> n = Symbol("n", integer=True, positive=True)
|
892 |
+
>>> loggamma(n)
|
893 |
+
log(gamma(n))
|
894 |
+
>>> loggamma(-n)
|
895 |
+
oo
|
896 |
+
|
897 |
+
For half-integral values:
|
898 |
+
|
899 |
+
>>> from sympy import S
|
900 |
+
>>> loggamma(S(5)/2)
|
901 |
+
log(3*sqrt(pi)/4)
|
902 |
+
>>> loggamma(n/2)
|
903 |
+
log(2**(1 - n)*sqrt(pi)*gamma(n)/gamma(n/2 + 1/2))
|
904 |
+
|
905 |
+
And general rational arguments:
|
906 |
+
|
907 |
+
>>> from sympy import expand_func
|
908 |
+
>>> L = loggamma(S(16)/3)
|
909 |
+
>>> expand_func(L).doit()
|
910 |
+
-5*log(3) + loggamma(1/3) + log(4) + log(7) + log(10) + log(13)
|
911 |
+
>>> L = loggamma(S(19)/4)
|
912 |
+
>>> expand_func(L).doit()
|
913 |
+
-4*log(4) + loggamma(3/4) + log(3) + log(7) + log(11) + log(15)
|
914 |
+
>>> L = loggamma(S(23)/7)
|
915 |
+
>>> expand_func(L).doit()
|
916 |
+
-3*log(7) + log(2) + loggamma(2/7) + log(9) + log(16)
|
917 |
+
|
918 |
+
The ``loggamma`` function has the following limits towards infinity:
|
919 |
+
|
920 |
+
>>> from sympy import oo
|
921 |
+
>>> loggamma(oo)
|
922 |
+
oo
|
923 |
+
>>> loggamma(-oo)
|
924 |
+
zoo
|
925 |
+
|
926 |
+
The ``loggamma`` function obeys the mirror symmetry
|
927 |
+
if $x \in \mathbb{C} \setminus \{-\infty, 0\}$:
|
928 |
+
|
929 |
+
>>> from sympy.abc import x
|
930 |
+
>>> from sympy import conjugate
|
931 |
+
>>> conjugate(loggamma(x))
|
932 |
+
loggamma(conjugate(x))
|
933 |
+
|
934 |
+
Differentiation with respect to $x$ is supported:
|
935 |
+
|
936 |
+
>>> from sympy import diff
|
937 |
+
>>> diff(loggamma(x), x)
|
938 |
+
polygamma(0, x)
|
939 |
+
|
940 |
+
Series expansion is also supported:
|
941 |
+
|
942 |
+
>>> from sympy import series
|
943 |
+
>>> series(loggamma(x), x, 0, 4).cancel()
|
944 |
+
-log(x) - EulerGamma*x + pi**2*x**2/12 - x**3*zeta(3)/3 + O(x**4)
|
945 |
+
|
946 |
+
We can numerically evaluate the ``loggamma`` function
|
947 |
+
to arbitrary precision on the whole complex plane:
|
948 |
+
|
949 |
+
>>> from sympy import I
|
950 |
+
>>> loggamma(5).evalf(30)
|
951 |
+
3.17805383034794561964694160130
|
952 |
+
>>> loggamma(I).evalf(20)
|
953 |
+
-0.65092319930185633889 - 1.8724366472624298171*I
|
954 |
+
|
955 |
+
See Also
|
956 |
+
========
|
957 |
+
|
958 |
+
gamma: Gamma function.
|
959 |
+
lowergamma: Lower incomplete gamma function.
|
960 |
+
uppergamma: Upper incomplete gamma function.
|
961 |
+
polygamma: Polygamma function.
|
962 |
+
digamma: Digamma function.
|
963 |
+
trigamma: Trigamma function.
|
964 |
+
beta: Euler Beta function.
|
965 |
+
|
966 |
+
References
|
967 |
+
==========
|
968 |
+
|
969 |
+
.. [1] https://en.wikipedia.org/wiki/Gamma_function
|
970 |
+
.. [2] https://dlmf.nist.gov/5
|
971 |
+
.. [3] https://mathworld.wolfram.com/LogGammaFunction.html
|
972 |
+
.. [4] https://functions.wolfram.com/GammaBetaErf/LogGamma/
|
973 |
+
|
974 |
+
"""
|
975 |
+
@classmethod
|
976 |
+
def eval(cls, z):
|
977 |
+
if z.is_integer:
|
978 |
+
if z.is_nonpositive:
|
979 |
+
return oo
|
980 |
+
elif z.is_positive:
|
981 |
+
return log(gamma(z))
|
982 |
+
elif z.is_rational:
|
983 |
+
p, q = z.as_numer_denom()
|
984 |
+
# Half-integral values:
|
985 |
+
if p.is_positive and q == 2:
|
986 |
+
return log(sqrt(pi) * 2**(1 - p) * gamma(p) / gamma((p + 1)*S.Half))
|
987 |
+
|
988 |
+
if z is oo:
|
989 |
+
return oo
|
990 |
+
elif abs(z) is oo:
|
991 |
+
return S.ComplexInfinity
|
992 |
+
if z is S.NaN:
|
993 |
+
return S.NaN
|
994 |
+
|
995 |
+
def _eval_expand_func(self, **hints):
|
996 |
+
from sympy.concrete.summations import Sum
|
997 |
+
z = self.args[0]
|
998 |
+
|
999 |
+
if z.is_Rational:
|
1000 |
+
p, q = z.as_numer_denom()
|
1001 |
+
# General rational arguments (u + p/q)
|
1002 |
+
# Split z as n + p/q with p < q
|
1003 |
+
n = p // q
|
1004 |
+
p = p - n*q
|
1005 |
+
if p.is_positive and q.is_positive and p < q:
|
1006 |
+
k = Dummy("k")
|
1007 |
+
if n.is_positive:
|
1008 |
+
return loggamma(p / q) - n*log(q) + Sum(log((k - 1)*q + p), (k, 1, n))
|
1009 |
+
elif n.is_negative:
|
1010 |
+
return loggamma(p / q) - n*log(q) + pi*I*n - Sum(log(k*q - p), (k, 1, -n))
|
1011 |
+
elif n.is_zero:
|
1012 |
+
return loggamma(p / q)
|
1013 |
+
|
1014 |
+
return self
|
1015 |
+
|
1016 |
+
def _eval_nseries(self, x, n, logx=None, cdir=0):
|
1017 |
+
x0 = self.args[0].limit(x, 0)
|
1018 |
+
if x0.is_zero:
|
1019 |
+
f = self._eval_rewrite_as_intractable(*self.args)
|
1020 |
+
return f._eval_nseries(x, n, logx)
|
1021 |
+
return super()._eval_nseries(x, n, logx)
|
1022 |
+
|
1023 |
+
def _eval_aseries(self, n, args0, x, logx):
|
1024 |
+
from sympy.series.order import Order
|
1025 |
+
if args0[0] != oo:
|
1026 |
+
return super()._eval_aseries(n, args0, x, logx)
|
1027 |
+
z = self.args[0]
|
1028 |
+
r = log(z)*(z - S.Half) - z + log(2*pi)/2
|
1029 |
+
l = [bernoulli(2*k) / (2*k*(2*k - 1)*z**(2*k - 1)) for k in range(1, n)]
|
1030 |
+
o = None
|
1031 |
+
if n == 0:
|
1032 |
+
o = Order(1, x)
|
1033 |
+
else:
|
1034 |
+
o = Order(1/z**n, x)
|
1035 |
+
# It is very inefficient to first add the order and then do the nseries
|
1036 |
+
return (r + Add(*l))._eval_nseries(x, n, logx) + o
|
1037 |
+
|
1038 |
+
def _eval_rewrite_as_intractable(self, z, **kwargs):
|
1039 |
+
return log(gamma(z))
|
1040 |
+
|
1041 |
+
def _eval_is_real(self):
|
1042 |
+
z = self.args[0]
|
1043 |
+
if z.is_positive:
|
1044 |
+
return True
|
1045 |
+
elif z.is_nonpositive:
|
1046 |
+
return False
|
1047 |
+
|
1048 |
+
def _eval_conjugate(self):
|
1049 |
+
z = self.args[0]
|
1050 |
+
if z not in (S.Zero, S.NegativeInfinity):
|
1051 |
+
return self.func(z.conjugate())
|
1052 |
+
|
1053 |
+
def fdiff(self, argindex=1):
|
1054 |
+
if argindex == 1:
|
1055 |
+
return polygamma(0, self.args[0])
|
1056 |
+
else:
|
1057 |
+
raise ArgumentIndexError(self, argindex)
|
1058 |
+
|
1059 |
+
|
1060 |
+
class digamma(Function):
|
1061 |
+
r"""
|
1062 |
+
The ``digamma`` function is the first derivative of the ``loggamma``
|
1063 |
+
function
|
1064 |
+
|
1065 |
+
.. math::
|
1066 |
+
\psi(x) := \frac{\mathrm{d}}{\mathrm{d} z} \log\Gamma(z)
|
1067 |
+
= \frac{\Gamma'(z)}{\Gamma(z) }.
|
1068 |
+
|
1069 |
+
In this case, ``digamma(z) = polygamma(0, z)``.
|
1070 |
+
|
1071 |
+
Examples
|
1072 |
+
========
|
1073 |
+
|
1074 |
+
>>> from sympy import digamma
|
1075 |
+
>>> digamma(0)
|
1076 |
+
zoo
|
1077 |
+
>>> from sympy import Symbol
|
1078 |
+
>>> z = Symbol('z')
|
1079 |
+
>>> digamma(z)
|
1080 |
+
polygamma(0, z)
|
1081 |
+
|
1082 |
+
To retain ``digamma`` as it is:
|
1083 |
+
|
1084 |
+
>>> digamma(0, evaluate=False)
|
1085 |
+
digamma(0)
|
1086 |
+
>>> digamma(z, evaluate=False)
|
1087 |
+
digamma(z)
|
1088 |
+
|
1089 |
+
See Also
|
1090 |
+
========
|
1091 |
+
|
1092 |
+
gamma: Gamma function.
|
1093 |
+
lowergamma: Lower incomplete gamma function.
|
1094 |
+
uppergamma: Upper incomplete gamma function.
|
1095 |
+
polygamma: Polygamma function.
|
1096 |
+
loggamma: Log Gamma function.
|
1097 |
+
trigamma: Trigamma function.
|
1098 |
+
beta: Euler Beta function.
|
1099 |
+
|
1100 |
+
References
|
1101 |
+
==========
|
1102 |
+
|
1103 |
+
.. [1] https://en.wikipedia.org/wiki/Digamma_function
|
1104 |
+
.. [2] https://mathworld.wolfram.com/DigammaFunction.html
|
1105 |
+
.. [3] https://functions.wolfram.com/GammaBetaErf/PolyGamma2/
|
1106 |
+
|
1107 |
+
"""
|
1108 |
+
def _eval_evalf(self, prec):
|
1109 |
+
z = self.args[0]
|
1110 |
+
nprec = prec_to_dps(prec)
|
1111 |
+
return polygamma(0, z).evalf(n=nprec)
|
1112 |
+
|
1113 |
+
def fdiff(self, argindex=1):
|
1114 |
+
z = self.args[0]
|
1115 |
+
return polygamma(0, z).fdiff()
|
1116 |
+
|
1117 |
+
def _eval_is_real(self):
|
1118 |
+
z = self.args[0]
|
1119 |
+
return polygamma(0, z).is_real
|
1120 |
+
|
1121 |
+
def _eval_is_positive(self):
|
1122 |
+
z = self.args[0]
|
1123 |
+
return polygamma(0, z).is_positive
|
1124 |
+
|
1125 |
+
def _eval_is_negative(self):
|
1126 |
+
z = self.args[0]
|
1127 |
+
return polygamma(0, z).is_negative
|
1128 |
+
|
1129 |
+
def _eval_aseries(self, n, args0, x, logx):
|
1130 |
+
as_polygamma = self.rewrite(polygamma)
|
1131 |
+
args0 = [S.Zero,] + args0
|
1132 |
+
return as_polygamma._eval_aseries(n, args0, x, logx)
|
1133 |
+
|
1134 |
+
@classmethod
|
1135 |
+
def eval(cls, z):
|
1136 |
+
return polygamma(0, z)
|
1137 |
+
|
1138 |
+
def _eval_expand_func(self, **hints):
|
1139 |
+
z = self.args[0]
|
1140 |
+
return polygamma(0, z).expand(func=True)
|
1141 |
+
|
1142 |
+
def _eval_rewrite_as_harmonic(self, z, **kwargs):
|
1143 |
+
return harmonic(z - 1) - S.EulerGamma
|
1144 |
+
|
1145 |
+
def _eval_rewrite_as_polygamma(self, z, **kwargs):
|
1146 |
+
return polygamma(0, z)
|
1147 |
+
|
1148 |
+
def _eval_as_leading_term(self, x, logx=None, cdir=0):
|
1149 |
+
z = self.args[0]
|
1150 |
+
return polygamma(0, z).as_leading_term(x)
|
1151 |
+
|
1152 |
+
|
1153 |
+
|
1154 |
+
class trigamma(Function):
|
1155 |
+
r"""
|
1156 |
+
The ``trigamma`` function is the second derivative of the ``loggamma``
|
1157 |
+
function
|
1158 |
+
|
1159 |
+
.. math::
|
1160 |
+
\psi^{(1)}(z) := \frac{\mathrm{d}^{2}}{\mathrm{d} z^{2}} \log\Gamma(z).
|
1161 |
+
|
1162 |
+
In this case, ``trigamma(z) = polygamma(1, z)``.
|
1163 |
+
|
1164 |
+
Examples
|
1165 |
+
========
|
1166 |
+
|
1167 |
+
>>> from sympy import trigamma
|
1168 |
+
>>> trigamma(0)
|
1169 |
+
zoo
|
1170 |
+
>>> from sympy import Symbol
|
1171 |
+
>>> z = Symbol('z')
|
1172 |
+
>>> trigamma(z)
|
1173 |
+
polygamma(1, z)
|
1174 |
+
|
1175 |
+
To retain ``trigamma`` as it is:
|
1176 |
+
|
1177 |
+
>>> trigamma(0, evaluate=False)
|
1178 |
+
trigamma(0)
|
1179 |
+
>>> trigamma(z, evaluate=False)
|
1180 |
+
trigamma(z)
|
1181 |
+
|
1182 |
+
|
1183 |
+
See Also
|
1184 |
+
========
|
1185 |
+
|
1186 |
+
gamma: Gamma function.
|
1187 |
+
lowergamma: Lower incomplete gamma function.
|
1188 |
+
uppergamma: Upper incomplete gamma function.
|
1189 |
+
polygamma: Polygamma function.
|
1190 |
+
loggamma: Log Gamma function.
|
1191 |
+
digamma: Digamma function.
|
1192 |
+
beta: Euler Beta function.
|
1193 |
+
|
1194 |
+
References
|
1195 |
+
==========
|
1196 |
+
|
1197 |
+
.. [1] https://en.wikipedia.org/wiki/Trigamma_function
|
1198 |
+
.. [2] https://mathworld.wolfram.com/TrigammaFunction.html
|
1199 |
+
.. [3] https://functions.wolfram.com/GammaBetaErf/PolyGamma2/
|
1200 |
+
|
1201 |
+
"""
|
1202 |
+
def _eval_evalf(self, prec):
|
1203 |
+
z = self.args[0]
|
1204 |
+
nprec = prec_to_dps(prec)
|
1205 |
+
return polygamma(1, z).evalf(n=nprec)
|
1206 |
+
|
1207 |
+
def fdiff(self, argindex=1):
|
1208 |
+
z = self.args[0]
|
1209 |
+
return polygamma(1, z).fdiff()
|
1210 |
+
|
1211 |
+
def _eval_is_real(self):
|
1212 |
+
z = self.args[0]
|
1213 |
+
return polygamma(1, z).is_real
|
1214 |
+
|
1215 |
+
def _eval_is_positive(self):
|
1216 |
+
z = self.args[0]
|
1217 |
+
return polygamma(1, z).is_positive
|
1218 |
+
|
1219 |
+
def _eval_is_negative(self):
|
1220 |
+
z = self.args[0]
|
1221 |
+
return polygamma(1, z).is_negative
|
1222 |
+
|
1223 |
+
def _eval_aseries(self, n, args0, x, logx):
|
1224 |
+
as_polygamma = self.rewrite(polygamma)
|
1225 |
+
args0 = [S.One,] + args0
|
1226 |
+
return as_polygamma._eval_aseries(n, args0, x, logx)
|
1227 |
+
|
1228 |
+
@classmethod
|
1229 |
+
def eval(cls, z):
|
1230 |
+
return polygamma(1, z)
|
1231 |
+
|
1232 |
+
def _eval_expand_func(self, **hints):
|
1233 |
+
z = self.args[0]
|
1234 |
+
return polygamma(1, z).expand(func=True)
|
1235 |
+
|
1236 |
+
def _eval_rewrite_as_zeta(self, z, **kwargs):
|
1237 |
+
return zeta(2, z)
|
1238 |
+
|
1239 |
+
def _eval_rewrite_as_polygamma(self, z, **kwargs):
|
1240 |
+
return polygamma(1, z)
|
1241 |
+
|
1242 |
+
def _eval_rewrite_as_harmonic(self, z, **kwargs):
|
1243 |
+
return -harmonic(z - 1, 2) + pi**2 / 6
|
1244 |
+
|
1245 |
+
def _eval_as_leading_term(self, x, logx=None, cdir=0):
|
1246 |
+
z = self.args[0]
|
1247 |
+
return polygamma(1, z).as_leading_term(x)
|
1248 |
+
|
1249 |
+
|
1250 |
+
###############################################################################
|
1251 |
+
##################### COMPLETE MULTIVARIATE GAMMA FUNCTION ####################
|
1252 |
+
###############################################################################
|
1253 |
+
|
1254 |
+
|
1255 |
+
class multigamma(Function):
|
1256 |
+
r"""
|
1257 |
+
The multivariate gamma function is a generalization of the gamma function
|
1258 |
+
|
1259 |
+
.. math::
|
1260 |
+
\Gamma_p(z) = \pi^{p(p-1)/4}\prod_{k=1}^p \Gamma[z + (1 - k)/2].
|
1261 |
+
|
1262 |
+
In a special case, ``multigamma(x, 1) = gamma(x)``.
|
1263 |
+
|
1264 |
+
Examples
|
1265 |
+
========
|
1266 |
+
|
1267 |
+
>>> from sympy import S, multigamma
|
1268 |
+
>>> from sympy import Symbol
|
1269 |
+
>>> x = Symbol('x')
|
1270 |
+
>>> p = Symbol('p', positive=True, integer=True)
|
1271 |
+
|
1272 |
+
>>> multigamma(x, p)
|
1273 |
+
pi**(p*(p - 1)/4)*Product(gamma(-_k/2 + x + 1/2), (_k, 1, p))
|
1274 |
+
|
1275 |
+
Several special values are known:
|
1276 |
+
|
1277 |
+
>>> multigamma(1, 1)
|
1278 |
+
1
|
1279 |
+
>>> multigamma(4, 1)
|
1280 |
+
6
|
1281 |
+
>>> multigamma(S(3)/2, 1)
|
1282 |
+
sqrt(pi)/2
|
1283 |
+
|
1284 |
+
Writing ``multigamma`` in terms of the ``gamma`` function:
|
1285 |
+
|
1286 |
+
>>> multigamma(x, 1)
|
1287 |
+
gamma(x)
|
1288 |
+
|
1289 |
+
>>> multigamma(x, 2)
|
1290 |
+
sqrt(pi)*gamma(x)*gamma(x - 1/2)
|
1291 |
+
|
1292 |
+
>>> multigamma(x, 3)
|
1293 |
+
pi**(3/2)*gamma(x)*gamma(x - 1)*gamma(x - 1/2)
|
1294 |
+
|
1295 |
+
Parameters
|
1296 |
+
==========
|
1297 |
+
|
1298 |
+
p : order or dimension of the multivariate gamma function
|
1299 |
+
|
1300 |
+
See Also
|
1301 |
+
========
|
1302 |
+
|
1303 |
+
gamma, lowergamma, uppergamma, polygamma, loggamma, digamma, trigamma,
|
1304 |
+
beta
|
1305 |
+
|
1306 |
+
References
|
1307 |
+
==========
|
1308 |
+
|
1309 |
+
.. [1] https://en.wikipedia.org/wiki/Multivariate_gamma_function
|
1310 |
+
|
1311 |
+
"""
|
1312 |
+
unbranched = True
|
1313 |
+
|
1314 |
+
def fdiff(self, argindex=2):
|
1315 |
+
from sympy.concrete.summations import Sum
|
1316 |
+
if argindex == 2:
|
1317 |
+
x, p = self.args
|
1318 |
+
k = Dummy("k")
|
1319 |
+
return self.func(x, p)*Sum(polygamma(0, x + (1 - k)/2), (k, 1, p))
|
1320 |
+
else:
|
1321 |
+
raise ArgumentIndexError(self, argindex)
|
1322 |
+
|
1323 |
+
@classmethod
|
1324 |
+
def eval(cls, x, p):
|
1325 |
+
from sympy.concrete.products import Product
|
1326 |
+
if p.is_positive is False or p.is_integer is False:
|
1327 |
+
raise ValueError('Order parameter p must be positive integer.')
|
1328 |
+
k = Dummy("k")
|
1329 |
+
return (pi**(p*(p - 1)/4)*Product(gamma(x + (1 - k)/2),
|
1330 |
+
(k, 1, p))).doit()
|
1331 |
+
|
1332 |
+
def _eval_conjugate(self):
|
1333 |
+
x, p = self.args
|
1334 |
+
return self.func(x.conjugate(), p)
|
1335 |
+
|
1336 |
+
def _eval_is_real(self):
|
1337 |
+
x, p = self.args
|
1338 |
+
y = 2*x
|
1339 |
+
if y.is_integer and (y <= (p - 1)) is True:
|
1340 |
+
return False
|
1341 |
+
if intlike(y) and (y <= (p - 1)):
|
1342 |
+
return False
|
1343 |
+
if y > (p - 1) or y.is_noninteger:
|
1344 |
+
return True
|
venv/lib/python3.10/site-packages/sympy/functions/special/hyper.py
ADDED
@@ -0,0 +1,1152 @@
|
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|
1 |
+
"""Hypergeometric and Meijer G-functions"""
|
2 |
+
from functools import reduce
|
3 |
+
|
4 |
+
from sympy.core import S, ilcm, Mod
|
5 |
+
from sympy.core.add import Add
|
6 |
+
from sympy.core.expr import Expr
|
7 |
+
from sympy.core.function import Function, Derivative, ArgumentIndexError
|
8 |
+
|
9 |
+
from sympy.core.containers import Tuple
|
10 |
+
from sympy.core.mul import Mul
|
11 |
+
from sympy.core.numbers import I, pi, oo, zoo
|
12 |
+
from sympy.core.relational import Ne
|
13 |
+
from sympy.core.sorting import default_sort_key
|
14 |
+
from sympy.core.symbol import Dummy
|
15 |
+
|
16 |
+
from sympy.functions import (sqrt, exp, log, sin, cos, asin, atan,
|
17 |
+
sinh, cosh, asinh, acosh, atanh, acoth)
|
18 |
+
from sympy.functions import factorial, RisingFactorial
|
19 |
+
from sympy.functions.elementary.complexes import Abs, re, unpolarify
|
20 |
+
from sympy.functions.elementary.exponential import exp_polar
|
21 |
+
from sympy.functions.elementary.integers import ceiling
|
22 |
+
from sympy.functions.elementary.piecewise import Piecewise
|
23 |
+
from sympy.logic.boolalg import (And, Or)
|
24 |
+
|
25 |
+
class TupleArg(Tuple):
|
26 |
+
def limit(self, x, xlim, dir='+'):
|
27 |
+
""" Compute limit x->xlim.
|
28 |
+
"""
|
29 |
+
from sympy.series.limits import limit
|
30 |
+
return TupleArg(*[limit(f, x, xlim, dir) for f in self.args])
|
31 |
+
|
32 |
+
|
33 |
+
# TODO should __new__ accept **options?
|
34 |
+
# TODO should constructors should check if parameters are sensible?
|
35 |
+
|
36 |
+
|
37 |
+
def _prep_tuple(v):
|
38 |
+
"""
|
39 |
+
Turn an iterable argument *v* into a tuple and unpolarify, since both
|
40 |
+
hypergeometric and meijer g-functions are unbranched in their parameters.
|
41 |
+
|
42 |
+
Examples
|
43 |
+
========
|
44 |
+
|
45 |
+
>>> from sympy.functions.special.hyper import _prep_tuple
|
46 |
+
>>> _prep_tuple([1, 2, 3])
|
47 |
+
(1, 2, 3)
|
48 |
+
>>> _prep_tuple((4, 5))
|
49 |
+
(4, 5)
|
50 |
+
>>> _prep_tuple((7, 8, 9))
|
51 |
+
(7, 8, 9)
|
52 |
+
|
53 |
+
"""
|
54 |
+
return TupleArg(*[unpolarify(x) for x in v])
|
55 |
+
|
56 |
+
|
57 |
+
class TupleParametersBase(Function):
|
58 |
+
""" Base class that takes care of differentiation, when some of
|
59 |
+
the arguments are actually tuples. """
|
60 |
+
# This is not deduced automatically since there are Tuples as arguments.
|
61 |
+
is_commutative = True
|
62 |
+
|
63 |
+
def _eval_derivative(self, s):
|
64 |
+
try:
|
65 |
+
res = 0
|
66 |
+
if self.args[0].has(s) or self.args[1].has(s):
|
67 |
+
for i, p in enumerate(self._diffargs):
|
68 |
+
m = self._diffargs[i].diff(s)
|
69 |
+
if m != 0:
|
70 |
+
res += self.fdiff((1, i))*m
|
71 |
+
return res + self.fdiff(3)*self.args[2].diff(s)
|
72 |
+
except (ArgumentIndexError, NotImplementedError):
|
73 |
+
return Derivative(self, s)
|
74 |
+
|
75 |
+
|
76 |
+
class hyper(TupleParametersBase):
|
77 |
+
r"""
|
78 |
+
The generalized hypergeometric function is defined by a series where
|
79 |
+
the ratios of successive terms are a rational function of the summation
|
80 |
+
index. When convergent, it is continued analytically to the largest
|
81 |
+
possible domain.
|
82 |
+
|
83 |
+
Explanation
|
84 |
+
===========
|
85 |
+
|
86 |
+
The hypergeometric function depends on two vectors of parameters, called
|
87 |
+
the numerator parameters $a_p$, and the denominator parameters
|
88 |
+
$b_q$. It also has an argument $z$. The series definition is
|
89 |
+
|
90 |
+
.. math ::
|
91 |
+
{}_pF_q\left(\begin{matrix} a_1, \cdots, a_p \\ b_1, \cdots, b_q \end{matrix}
|
92 |
+
\middle| z \right)
|
93 |
+
= \sum_{n=0}^\infty \frac{(a_1)_n \cdots (a_p)_n}{(b_1)_n \cdots (b_q)_n}
|
94 |
+
\frac{z^n}{n!},
|
95 |
+
|
96 |
+
where $(a)_n = (a)(a+1)\cdots(a+n-1)$ denotes the rising factorial.
|
97 |
+
|
98 |
+
If one of the $b_q$ is a non-positive integer then the series is
|
99 |
+
undefined unless one of the $a_p$ is a larger (i.e., smaller in
|
100 |
+
magnitude) non-positive integer. If none of the $b_q$ is a
|
101 |
+
non-positive integer and one of the $a_p$ is a non-positive
|
102 |
+
integer, then the series reduces to a polynomial. To simplify the
|
103 |
+
following discussion, we assume that none of the $a_p$ or
|
104 |
+
$b_q$ is a non-positive integer. For more details, see the
|
105 |
+
references.
|
106 |
+
|
107 |
+
The series converges for all $z$ if $p \le q$, and thus
|
108 |
+
defines an entire single-valued function in this case. If $p =
|
109 |
+
q+1$ the series converges for $|z| < 1$, and can be continued
|
110 |
+
analytically into a half-plane. If $p > q+1$ the series is
|
111 |
+
divergent for all $z$.
|
112 |
+
|
113 |
+
Please note the hypergeometric function constructor currently does *not*
|
114 |
+
check if the parameters actually yield a well-defined function.
|
115 |
+
|
116 |
+
Examples
|
117 |
+
========
|
118 |
+
|
119 |
+
The parameters $a_p$ and $b_q$ can be passed as arbitrary
|
120 |
+
iterables, for example:
|
121 |
+
|
122 |
+
>>> from sympy import hyper
|
123 |
+
>>> from sympy.abc import x, n, a
|
124 |
+
>>> hyper((1, 2, 3), [3, 4], x)
|
125 |
+
hyper((1, 2, 3), (3, 4), x)
|
126 |
+
|
127 |
+
There is also pretty printing (it looks better using Unicode):
|
128 |
+
|
129 |
+
>>> from sympy import pprint
|
130 |
+
>>> pprint(hyper((1, 2, 3), [3, 4], x), use_unicode=False)
|
131 |
+
_
|
132 |
+
|_ /1, 2, 3 | \
|
133 |
+
| | | x|
|
134 |
+
3 2 \ 3, 4 | /
|
135 |
+
|
136 |
+
The parameters must always be iterables, even if they are vectors of
|
137 |
+
length one or zero:
|
138 |
+
|
139 |
+
>>> hyper((1, ), [], x)
|
140 |
+
hyper((1,), (), x)
|
141 |
+
|
142 |
+
But of course they may be variables (but if they depend on $x$ then you
|
143 |
+
should not expect much implemented functionality):
|
144 |
+
|
145 |
+
>>> hyper((n, a), (n**2,), x)
|
146 |
+
hyper((n, a), (n**2,), x)
|
147 |
+
|
148 |
+
The hypergeometric function generalizes many named special functions.
|
149 |
+
The function ``hyperexpand()`` tries to express a hypergeometric function
|
150 |
+
using named special functions. For example:
|
151 |
+
|
152 |
+
>>> from sympy import hyperexpand
|
153 |
+
>>> hyperexpand(hyper([], [], x))
|
154 |
+
exp(x)
|
155 |
+
|
156 |
+
You can also use ``expand_func()``:
|
157 |
+
|
158 |
+
>>> from sympy import expand_func
|
159 |
+
>>> expand_func(x*hyper([1, 1], [2], -x))
|
160 |
+
log(x + 1)
|
161 |
+
|
162 |
+
More examples:
|
163 |
+
|
164 |
+
>>> from sympy import S
|
165 |
+
>>> hyperexpand(hyper([], [S(1)/2], -x**2/4))
|
166 |
+
cos(x)
|
167 |
+
>>> hyperexpand(x*hyper([S(1)/2, S(1)/2], [S(3)/2], x**2))
|
168 |
+
asin(x)
|
169 |
+
|
170 |
+
We can also sometimes ``hyperexpand()`` parametric functions:
|
171 |
+
|
172 |
+
>>> from sympy.abc import a
|
173 |
+
>>> hyperexpand(hyper([-a], [], x))
|
174 |
+
(1 - x)**a
|
175 |
+
|
176 |
+
See Also
|
177 |
+
========
|
178 |
+
|
179 |
+
sympy.simplify.hyperexpand
|
180 |
+
gamma
|
181 |
+
meijerg
|
182 |
+
|
183 |
+
References
|
184 |
+
==========
|
185 |
+
|
186 |
+
.. [1] Luke, Y. L. (1969), The Special Functions and Their Approximations,
|
187 |
+
Volume 1
|
188 |
+
.. [2] https://en.wikipedia.org/wiki/Generalized_hypergeometric_function
|
189 |
+
|
190 |
+
"""
|
191 |
+
|
192 |
+
|
193 |
+
def __new__(cls, ap, bq, z, **kwargs):
|
194 |
+
# TODO should we check convergence conditions?
|
195 |
+
return Function.__new__(cls, _prep_tuple(ap), _prep_tuple(bq), z, **kwargs)
|
196 |
+
|
197 |
+
@classmethod
|
198 |
+
def eval(cls, ap, bq, z):
|
199 |
+
if len(ap) <= len(bq) or (len(ap) == len(bq) + 1 and (Abs(z) <= 1) == True):
|
200 |
+
nz = unpolarify(z)
|
201 |
+
if z != nz:
|
202 |
+
return hyper(ap, bq, nz)
|
203 |
+
|
204 |
+
def fdiff(self, argindex=3):
|
205 |
+
if argindex != 3:
|
206 |
+
raise ArgumentIndexError(self, argindex)
|
207 |
+
nap = Tuple(*[a + 1 for a in self.ap])
|
208 |
+
nbq = Tuple(*[b + 1 for b in self.bq])
|
209 |
+
fac = Mul(*self.ap)/Mul(*self.bq)
|
210 |
+
return fac*hyper(nap, nbq, self.argument)
|
211 |
+
|
212 |
+
def _eval_expand_func(self, **hints):
|
213 |
+
from sympy.functions.special.gamma_functions import gamma
|
214 |
+
from sympy.simplify.hyperexpand import hyperexpand
|
215 |
+
if len(self.ap) == 2 and len(self.bq) == 1 and self.argument == 1:
|
216 |
+
a, b = self.ap
|
217 |
+
c = self.bq[0]
|
218 |
+
return gamma(c)*gamma(c - a - b)/gamma(c - a)/gamma(c - b)
|
219 |
+
return hyperexpand(self)
|
220 |
+
|
221 |
+
def _eval_rewrite_as_Sum(self, ap, bq, z, **kwargs):
|
222 |
+
from sympy.concrete.summations import Sum
|
223 |
+
n = Dummy("n", integer=True)
|
224 |
+
rfap = [RisingFactorial(a, n) for a in ap]
|
225 |
+
rfbq = [RisingFactorial(b, n) for b in bq]
|
226 |
+
coeff = Mul(*rfap) / Mul(*rfbq)
|
227 |
+
return Piecewise((Sum(coeff * z**n / factorial(n), (n, 0, oo)),
|
228 |
+
self.convergence_statement), (self, True))
|
229 |
+
|
230 |
+
def _eval_as_leading_term(self, x, logx=None, cdir=0):
|
231 |
+
arg = self.args[2]
|
232 |
+
x0 = arg.subs(x, 0)
|
233 |
+
if x0 is S.NaN:
|
234 |
+
x0 = arg.limit(x, 0, dir='-' if re(cdir).is_negative else '+')
|
235 |
+
|
236 |
+
if x0 is S.Zero:
|
237 |
+
return S.One
|
238 |
+
return super()._eval_as_leading_term(x, logx=logx, cdir=cdir)
|
239 |
+
|
240 |
+
def _eval_nseries(self, x, n, logx, cdir=0):
|
241 |
+
|
242 |
+
from sympy.series.order import Order
|
243 |
+
|
244 |
+
arg = self.args[2]
|
245 |
+
x0 = arg.limit(x, 0)
|
246 |
+
ap = self.args[0]
|
247 |
+
bq = self.args[1]
|
248 |
+
|
249 |
+
if x0 != 0:
|
250 |
+
return super()._eval_nseries(x, n, logx)
|
251 |
+
|
252 |
+
terms = []
|
253 |
+
|
254 |
+
for i in range(n):
|
255 |
+
num = Mul(*[RisingFactorial(a, i) for a in ap])
|
256 |
+
den = Mul(*[RisingFactorial(b, i) for b in bq])
|
257 |
+
terms.append(((num/den) * (arg**i)) / factorial(i))
|
258 |
+
|
259 |
+
return (Add(*terms) + Order(x**n,x))
|
260 |
+
|
261 |
+
@property
|
262 |
+
def argument(self):
|
263 |
+
""" Argument of the hypergeometric function. """
|
264 |
+
return self.args[2]
|
265 |
+
|
266 |
+
@property
|
267 |
+
def ap(self):
|
268 |
+
""" Numerator parameters of the hypergeometric function. """
|
269 |
+
return Tuple(*self.args[0])
|
270 |
+
|
271 |
+
@property
|
272 |
+
def bq(self):
|
273 |
+
""" Denominator parameters of the hypergeometric function. """
|
274 |
+
return Tuple(*self.args[1])
|
275 |
+
|
276 |
+
@property
|
277 |
+
def _diffargs(self):
|
278 |
+
return self.ap + self.bq
|
279 |
+
|
280 |
+
@property
|
281 |
+
def eta(self):
|
282 |
+
""" A quantity related to the convergence of the series. """
|
283 |
+
return sum(self.ap) - sum(self.bq)
|
284 |
+
|
285 |
+
@property
|
286 |
+
def radius_of_convergence(self):
|
287 |
+
"""
|
288 |
+
Compute the radius of convergence of the defining series.
|
289 |
+
|
290 |
+
Explanation
|
291 |
+
===========
|
292 |
+
|
293 |
+
Note that even if this is not ``oo``, the function may still be
|
294 |
+
evaluated outside of the radius of convergence by analytic
|
295 |
+
continuation. But if this is zero, then the function is not actually
|
296 |
+
defined anywhere else.
|
297 |
+
|
298 |
+
Examples
|
299 |
+
========
|
300 |
+
|
301 |
+
>>> from sympy import hyper
|
302 |
+
>>> from sympy.abc import z
|
303 |
+
>>> hyper((1, 2), [3], z).radius_of_convergence
|
304 |
+
1
|
305 |
+
>>> hyper((1, 2, 3), [4], z).radius_of_convergence
|
306 |
+
0
|
307 |
+
>>> hyper((1, 2), (3, 4), z).radius_of_convergence
|
308 |
+
oo
|
309 |
+
|
310 |
+
"""
|
311 |
+
if any(a.is_integer and (a <= 0) == True for a in self.ap + self.bq):
|
312 |
+
aints = [a for a in self.ap if a.is_Integer and (a <= 0) == True]
|
313 |
+
bints = [a for a in self.bq if a.is_Integer and (a <= 0) == True]
|
314 |
+
if len(aints) < len(bints):
|
315 |
+
return S.Zero
|
316 |
+
popped = False
|
317 |
+
for b in bints:
|
318 |
+
cancelled = False
|
319 |
+
while aints:
|
320 |
+
a = aints.pop()
|
321 |
+
if a >= b:
|
322 |
+
cancelled = True
|
323 |
+
break
|
324 |
+
popped = True
|
325 |
+
if not cancelled:
|
326 |
+
return S.Zero
|
327 |
+
if aints or popped:
|
328 |
+
# There are still non-positive numerator parameters.
|
329 |
+
# This is a polynomial.
|
330 |
+
return oo
|
331 |
+
if len(self.ap) == len(self.bq) + 1:
|
332 |
+
return S.One
|
333 |
+
elif len(self.ap) <= len(self.bq):
|
334 |
+
return oo
|
335 |
+
else:
|
336 |
+
return S.Zero
|
337 |
+
|
338 |
+
@property
|
339 |
+
def convergence_statement(self):
|
340 |
+
""" Return a condition on z under which the series converges. """
|
341 |
+
R = self.radius_of_convergence
|
342 |
+
if R == 0:
|
343 |
+
return False
|
344 |
+
if R == oo:
|
345 |
+
return True
|
346 |
+
# The special functions and their approximations, page 44
|
347 |
+
e = self.eta
|
348 |
+
z = self.argument
|
349 |
+
c1 = And(re(e) < 0, abs(z) <= 1)
|
350 |
+
c2 = And(0 <= re(e), re(e) < 1, abs(z) <= 1, Ne(z, 1))
|
351 |
+
c3 = And(re(e) >= 1, abs(z) < 1)
|
352 |
+
return Or(c1, c2, c3)
|
353 |
+
|
354 |
+
def _eval_simplify(self, **kwargs):
|
355 |
+
from sympy.simplify.hyperexpand import hyperexpand
|
356 |
+
return hyperexpand(self)
|
357 |
+
|
358 |
+
|
359 |
+
class meijerg(TupleParametersBase):
|
360 |
+
r"""
|
361 |
+
The Meijer G-function is defined by a Mellin-Barnes type integral that
|
362 |
+
resembles an inverse Mellin transform. It generalizes the hypergeometric
|
363 |
+
functions.
|
364 |
+
|
365 |
+
Explanation
|
366 |
+
===========
|
367 |
+
|
368 |
+
The Meijer G-function depends on four sets of parameters. There are
|
369 |
+
"*numerator parameters*"
|
370 |
+
$a_1, \ldots, a_n$ and $a_{n+1}, \ldots, a_p$, and there are
|
371 |
+
"*denominator parameters*"
|
372 |
+
$b_1, \ldots, b_m$ and $b_{m+1}, \ldots, b_q$.
|
373 |
+
Confusingly, it is traditionally denoted as follows (note the position
|
374 |
+
of $m$, $n$, $p$, $q$, and how they relate to the lengths of the four
|
375 |
+
parameter vectors):
|
376 |
+
|
377 |
+
.. math ::
|
378 |
+
G_{p,q}^{m,n} \left(\begin{matrix}a_1, \cdots, a_n & a_{n+1}, \cdots, a_p \\
|
379 |
+
b_1, \cdots, b_m & b_{m+1}, \cdots, b_q
|
380 |
+
\end{matrix} \middle| z \right).
|
381 |
+
|
382 |
+
However, in SymPy the four parameter vectors are always available
|
383 |
+
separately (see examples), so that there is no need to keep track of the
|
384 |
+
decorating sub- and super-scripts on the G symbol.
|
385 |
+
|
386 |
+
The G function is defined as the following integral:
|
387 |
+
|
388 |
+
.. math ::
|
389 |
+
\frac{1}{2 \pi i} \int_L \frac{\prod_{j=1}^m \Gamma(b_j - s)
|
390 |
+
\prod_{j=1}^n \Gamma(1 - a_j + s)}{\prod_{j=m+1}^q \Gamma(1- b_j +s)
|
391 |
+
\prod_{j=n+1}^p \Gamma(a_j - s)} z^s \mathrm{d}s,
|
392 |
+
|
393 |
+
where $\Gamma(z)$ is the gamma function. There are three possible
|
394 |
+
contours which we will not describe in detail here (see the references).
|
395 |
+
If the integral converges along more than one of them, the definitions
|
396 |
+
agree. The contours all separate the poles of $\Gamma(1-a_j+s)$
|
397 |
+
from the poles of $\Gamma(b_k-s)$, so in particular the G function
|
398 |
+
is undefined if $a_j - b_k \in \mathbb{Z}_{>0}$ for some
|
399 |
+
$j \le n$ and $k \le m$.
|
400 |
+
|
401 |
+
The conditions under which one of the contours yields a convergent integral
|
402 |
+
are complicated and we do not state them here, see the references.
|
403 |
+
|
404 |
+
Please note currently the Meijer G-function constructor does *not* check any
|
405 |
+
convergence conditions.
|
406 |
+
|
407 |
+
Examples
|
408 |
+
========
|
409 |
+
|
410 |
+
You can pass the parameters either as four separate vectors:
|
411 |
+
|
412 |
+
>>> from sympy import meijerg, Tuple, pprint
|
413 |
+
>>> from sympy.abc import x, a
|
414 |
+
>>> pprint(meijerg((1, 2), (a, 4), (5,), [], x), use_unicode=False)
|
415 |
+
__1, 2 /1, 2 a, 4 | \
|
416 |
+
/__ | | x|
|
417 |
+
\_|4, 1 \ 5 | /
|
418 |
+
|
419 |
+
Or as two nested vectors:
|
420 |
+
|
421 |
+
>>> pprint(meijerg([(1, 2), (3, 4)], ([5], Tuple()), x), use_unicode=False)
|
422 |
+
__1, 2 /1, 2 3, 4 | \
|
423 |
+
/__ | | x|
|
424 |
+
\_|4, 1 \ 5 | /
|
425 |
+
|
426 |
+
As with the hypergeometric function, the parameters may be passed as
|
427 |
+
arbitrary iterables. Vectors of length zero and one also have to be
|
428 |
+
passed as iterables. The parameters need not be constants, but if they
|
429 |
+
depend on the argument then not much implemented functionality should be
|
430 |
+
expected.
|
431 |
+
|
432 |
+
All the subvectors of parameters are available:
|
433 |
+
|
434 |
+
>>> from sympy import pprint
|
435 |
+
>>> g = meijerg([1], [2], [3], [4], x)
|
436 |
+
>>> pprint(g, use_unicode=False)
|
437 |
+
__1, 1 /1 2 | \
|
438 |
+
/__ | | x|
|
439 |
+
\_|2, 2 \3 4 | /
|
440 |
+
>>> g.an
|
441 |
+
(1,)
|
442 |
+
>>> g.ap
|
443 |
+
(1, 2)
|
444 |
+
>>> g.aother
|
445 |
+
(2,)
|
446 |
+
>>> g.bm
|
447 |
+
(3,)
|
448 |
+
>>> g.bq
|
449 |
+
(3, 4)
|
450 |
+
>>> g.bother
|
451 |
+
(4,)
|
452 |
+
|
453 |
+
The Meijer G-function generalizes the hypergeometric functions.
|
454 |
+
In some cases it can be expressed in terms of hypergeometric functions,
|
455 |
+
using Slater's theorem. For example:
|
456 |
+
|
457 |
+
>>> from sympy import hyperexpand
|
458 |
+
>>> from sympy.abc import a, b, c
|
459 |
+
>>> hyperexpand(meijerg([a], [], [c], [b], x), allow_hyper=True)
|
460 |
+
x**c*gamma(-a + c + 1)*hyper((-a + c + 1,),
|
461 |
+
(-b + c + 1,), -x)/gamma(-b + c + 1)
|
462 |
+
|
463 |
+
Thus the Meijer G-function also subsumes many named functions as special
|
464 |
+
cases. You can use ``expand_func()`` or ``hyperexpand()`` to (try to)
|
465 |
+
rewrite a Meijer G-function in terms of named special functions. For
|
466 |
+
example:
|
467 |
+
|
468 |
+
>>> from sympy import expand_func, S
|
469 |
+
>>> expand_func(meijerg([[],[]], [[0],[]], -x))
|
470 |
+
exp(x)
|
471 |
+
>>> hyperexpand(meijerg([[],[]], [[S(1)/2],[0]], (x/2)**2))
|
472 |
+
sin(x)/sqrt(pi)
|
473 |
+
|
474 |
+
See Also
|
475 |
+
========
|
476 |
+
|
477 |
+
hyper
|
478 |
+
sympy.simplify.hyperexpand
|
479 |
+
|
480 |
+
References
|
481 |
+
==========
|
482 |
+
|
483 |
+
.. [1] Luke, Y. L. (1969), The Special Functions and Their Approximations,
|
484 |
+
Volume 1
|
485 |
+
.. [2] https://en.wikipedia.org/wiki/Meijer_G-function
|
486 |
+
|
487 |
+
"""
|
488 |
+
|
489 |
+
|
490 |
+
def __new__(cls, *args, **kwargs):
|
491 |
+
if len(args) == 5:
|
492 |
+
args = [(args[0], args[1]), (args[2], args[3]), args[4]]
|
493 |
+
if len(args) != 3:
|
494 |
+
raise TypeError("args must be either as, as', bs, bs', z or "
|
495 |
+
"as, bs, z")
|
496 |
+
|
497 |
+
def tr(p):
|
498 |
+
if len(p) != 2:
|
499 |
+
raise TypeError("wrong argument")
|
500 |
+
return TupleArg(_prep_tuple(p[0]), _prep_tuple(p[1]))
|
501 |
+
|
502 |
+
arg0, arg1 = tr(args[0]), tr(args[1])
|
503 |
+
if Tuple(arg0, arg1).has(oo, zoo, -oo):
|
504 |
+
raise ValueError("G-function parameters must be finite")
|
505 |
+
if any((a - b).is_Integer and a - b > 0
|
506 |
+
for a in arg0[0] for b in arg1[0]):
|
507 |
+
raise ValueError("no parameter a1, ..., an may differ from "
|
508 |
+
"any b1, ..., bm by a positive integer")
|
509 |
+
|
510 |
+
# TODO should we check convergence conditions?
|
511 |
+
return Function.__new__(cls, arg0, arg1, args[2], **kwargs)
|
512 |
+
|
513 |
+
def fdiff(self, argindex=3):
|
514 |
+
if argindex != 3:
|
515 |
+
return self._diff_wrt_parameter(argindex[1])
|
516 |
+
if len(self.an) >= 1:
|
517 |
+
a = list(self.an)
|
518 |
+
a[0] -= 1
|
519 |
+
G = meijerg(a, self.aother, self.bm, self.bother, self.argument)
|
520 |
+
return 1/self.argument * ((self.an[0] - 1)*self + G)
|
521 |
+
elif len(self.bm) >= 1:
|
522 |
+
b = list(self.bm)
|
523 |
+
b[0] += 1
|
524 |
+
G = meijerg(self.an, self.aother, b, self.bother, self.argument)
|
525 |
+
return 1/self.argument * (self.bm[0]*self - G)
|
526 |
+
else:
|
527 |
+
return S.Zero
|
528 |
+
|
529 |
+
def _diff_wrt_parameter(self, idx):
|
530 |
+
# Differentiation wrt a parameter can only be done in very special
|
531 |
+
# cases. In particular, if we want to differentiate with respect to
|
532 |
+
# `a`, all other gamma factors have to reduce to rational functions.
|
533 |
+
#
|
534 |
+
# Let MT denote mellin transform. Suppose T(-s) is the gamma factor
|
535 |
+
# appearing in the definition of G. Then
|
536 |
+
#
|
537 |
+
# MT(log(z)G(z)) = d/ds T(s) = d/da T(s) + ...
|
538 |
+
#
|
539 |
+
# Thus d/da G(z) = log(z)G(z) - ...
|
540 |
+
# The ... can be evaluated as a G function under the above conditions,
|
541 |
+
# the formula being most easily derived by using
|
542 |
+
#
|
543 |
+
# d Gamma(s + n) Gamma(s + n) / 1 1 1 \
|
544 |
+
# -- ------------ = ------------ | - + ---- + ... + --------- |
|
545 |
+
# ds Gamma(s) Gamma(s) \ s s + 1 s + n - 1 /
|
546 |
+
#
|
547 |
+
# which follows from the difference equation of the digamma function.
|
548 |
+
# (There is a similar equation for -n instead of +n).
|
549 |
+
|
550 |
+
# We first figure out how to pair the parameters.
|
551 |
+
an = list(self.an)
|
552 |
+
ap = list(self.aother)
|
553 |
+
bm = list(self.bm)
|
554 |
+
bq = list(self.bother)
|
555 |
+
if idx < len(an):
|
556 |
+
an.pop(idx)
|
557 |
+
else:
|
558 |
+
idx -= len(an)
|
559 |
+
if idx < len(ap):
|
560 |
+
ap.pop(idx)
|
561 |
+
else:
|
562 |
+
idx -= len(ap)
|
563 |
+
if idx < len(bm):
|
564 |
+
bm.pop(idx)
|
565 |
+
else:
|
566 |
+
bq.pop(idx - len(bm))
|
567 |
+
pairs1 = []
|
568 |
+
pairs2 = []
|
569 |
+
for l1, l2, pairs in [(an, bq, pairs1), (ap, bm, pairs2)]:
|
570 |
+
while l1:
|
571 |
+
x = l1.pop()
|
572 |
+
found = None
|
573 |
+
for i, y in enumerate(l2):
|
574 |
+
if not Mod((x - y).simplify(), 1):
|
575 |
+
found = i
|
576 |
+
break
|
577 |
+
if found is None:
|
578 |
+
raise NotImplementedError('Derivative not expressible '
|
579 |
+
'as G-function?')
|
580 |
+
y = l2[i]
|
581 |
+
l2.pop(i)
|
582 |
+
pairs.append((x, y))
|
583 |
+
|
584 |
+
# Now build the result.
|
585 |
+
res = log(self.argument)*self
|
586 |
+
|
587 |
+
for a, b in pairs1:
|
588 |
+
sign = 1
|
589 |
+
n = a - b
|
590 |
+
base = b
|
591 |
+
if n < 0:
|
592 |
+
sign = -1
|
593 |
+
n = b - a
|
594 |
+
base = a
|
595 |
+
for k in range(n):
|
596 |
+
res -= sign*meijerg(self.an + (base + k + 1,), self.aother,
|
597 |
+
self.bm, self.bother + (base + k + 0,),
|
598 |
+
self.argument)
|
599 |
+
|
600 |
+
for a, b in pairs2:
|
601 |
+
sign = 1
|
602 |
+
n = b - a
|
603 |
+
base = a
|
604 |
+
if n < 0:
|
605 |
+
sign = -1
|
606 |
+
n = a - b
|
607 |
+
base = b
|
608 |
+
for k in range(n):
|
609 |
+
res -= sign*meijerg(self.an, self.aother + (base + k + 1,),
|
610 |
+
self.bm + (base + k + 0,), self.bother,
|
611 |
+
self.argument)
|
612 |
+
|
613 |
+
return res
|
614 |
+
|
615 |
+
def get_period(self):
|
616 |
+
"""
|
617 |
+
Return a number $P$ such that $G(x*exp(I*P)) == G(x)$.
|
618 |
+
|
619 |
+
Examples
|
620 |
+
========
|
621 |
+
|
622 |
+
>>> from sympy import meijerg, pi, S
|
623 |
+
>>> from sympy.abc import z
|
624 |
+
|
625 |
+
>>> meijerg([1], [], [], [], z).get_period()
|
626 |
+
2*pi
|
627 |
+
>>> meijerg([pi], [], [], [], z).get_period()
|
628 |
+
oo
|
629 |
+
>>> meijerg([1, 2], [], [], [], z).get_period()
|
630 |
+
oo
|
631 |
+
>>> meijerg([1,1], [2], [1, S(1)/2, S(1)/3], [1], z).get_period()
|
632 |
+
12*pi
|
633 |
+
|
634 |
+
"""
|
635 |
+
# This follows from slater's theorem.
|
636 |
+
def compute(l):
|
637 |
+
# first check that no two differ by an integer
|
638 |
+
for i, b in enumerate(l):
|
639 |
+
if not b.is_Rational:
|
640 |
+
return oo
|
641 |
+
for j in range(i + 1, len(l)):
|
642 |
+
if not Mod((b - l[j]).simplify(), 1):
|
643 |
+
return oo
|
644 |
+
return reduce(ilcm, (x.q for x in l), 1)
|
645 |
+
beta = compute(self.bm)
|
646 |
+
alpha = compute(self.an)
|
647 |
+
p, q = len(self.ap), len(self.bq)
|
648 |
+
if p == q:
|
649 |
+
if oo in (alpha, beta):
|
650 |
+
return oo
|
651 |
+
return 2*pi*ilcm(alpha, beta)
|
652 |
+
elif p < q:
|
653 |
+
return 2*pi*beta
|
654 |
+
else:
|
655 |
+
return 2*pi*alpha
|
656 |
+
|
657 |
+
def _eval_expand_func(self, **hints):
|
658 |
+
from sympy.simplify.hyperexpand import hyperexpand
|
659 |
+
return hyperexpand(self)
|
660 |
+
|
661 |
+
def _eval_evalf(self, prec):
|
662 |
+
# The default code is insufficient for polar arguments.
|
663 |
+
# mpmath provides an optional argument "r", which evaluates
|
664 |
+
# G(z**(1/r)). I am not sure what its intended use is, but we hijack it
|
665 |
+
# here in the following way: to evaluate at a number z of |argument|
|
666 |
+
# less than (say) n*pi, we put r=1/n, compute z' = root(z, n)
|
667 |
+
# (carefully so as not to loose the branch information), and evaluate
|
668 |
+
# G(z'**(1/r)) = G(z'**n) = G(z).
|
669 |
+
import mpmath
|
670 |
+
znum = self.argument._eval_evalf(prec)
|
671 |
+
if znum.has(exp_polar):
|
672 |
+
znum, branch = znum.as_coeff_mul(exp_polar)
|
673 |
+
if len(branch) != 1:
|
674 |
+
return
|
675 |
+
branch = branch[0].args[0]/I
|
676 |
+
else:
|
677 |
+
branch = S.Zero
|
678 |
+
n = ceiling(abs(branch/pi)) + 1
|
679 |
+
znum = znum**(S.One/n)*exp(I*branch / n)
|
680 |
+
|
681 |
+
# Convert all args to mpf or mpc
|
682 |
+
try:
|
683 |
+
[z, r, ap, bq] = [arg._to_mpmath(prec)
|
684 |
+
for arg in [znum, 1/n, self.args[0], self.args[1]]]
|
685 |
+
except ValueError:
|
686 |
+
return
|
687 |
+
|
688 |
+
with mpmath.workprec(prec):
|
689 |
+
v = mpmath.meijerg(ap, bq, z, r)
|
690 |
+
|
691 |
+
return Expr._from_mpmath(v, prec)
|
692 |
+
|
693 |
+
def _eval_as_leading_term(self, x, logx=None, cdir=0):
|
694 |
+
from sympy.simplify.hyperexpand import hyperexpand
|
695 |
+
return hyperexpand(self).as_leading_term(x, logx=logx, cdir=cdir)
|
696 |
+
|
697 |
+
def integrand(self, s):
|
698 |
+
""" Get the defining integrand D(s). """
|
699 |
+
from sympy.functions.special.gamma_functions import gamma
|
700 |
+
return self.argument**s \
|
701 |
+
* Mul(*(gamma(b - s) for b in self.bm)) \
|
702 |
+
* Mul(*(gamma(1 - a + s) for a in self.an)) \
|
703 |
+
/ Mul(*(gamma(1 - b + s) for b in self.bother)) \
|
704 |
+
/ Mul(*(gamma(a - s) for a in self.aother))
|
705 |
+
|
706 |
+
@property
|
707 |
+
def argument(self):
|
708 |
+
""" Argument of the Meijer G-function. """
|
709 |
+
return self.args[2]
|
710 |
+
|
711 |
+
@property
|
712 |
+
def an(self):
|
713 |
+
""" First set of numerator parameters. """
|
714 |
+
return Tuple(*self.args[0][0])
|
715 |
+
|
716 |
+
@property
|
717 |
+
def ap(self):
|
718 |
+
""" Combined numerator parameters. """
|
719 |
+
return Tuple(*(self.args[0][0] + self.args[0][1]))
|
720 |
+
|
721 |
+
@property
|
722 |
+
def aother(self):
|
723 |
+
""" Second set of numerator parameters. """
|
724 |
+
return Tuple(*self.args[0][1])
|
725 |
+
|
726 |
+
@property
|
727 |
+
def bm(self):
|
728 |
+
""" First set of denominator parameters. """
|
729 |
+
return Tuple(*self.args[1][0])
|
730 |
+
|
731 |
+
@property
|
732 |
+
def bq(self):
|
733 |
+
""" Combined denominator parameters. """
|
734 |
+
return Tuple(*(self.args[1][0] + self.args[1][1]))
|
735 |
+
|
736 |
+
@property
|
737 |
+
def bother(self):
|
738 |
+
""" Second set of denominator parameters. """
|
739 |
+
return Tuple(*self.args[1][1])
|
740 |
+
|
741 |
+
@property
|
742 |
+
def _diffargs(self):
|
743 |
+
return self.ap + self.bq
|
744 |
+
|
745 |
+
@property
|
746 |
+
def nu(self):
|
747 |
+
""" A quantity related to the convergence region of the integral,
|
748 |
+
c.f. references. """
|
749 |
+
return sum(self.bq) - sum(self.ap)
|
750 |
+
|
751 |
+
@property
|
752 |
+
def delta(self):
|
753 |
+
""" A quantity related to the convergence region of the integral,
|
754 |
+
c.f. references. """
|
755 |
+
return len(self.bm) + len(self.an) - S(len(self.ap) + len(self.bq))/2
|
756 |
+
|
757 |
+
@property
|
758 |
+
def is_number(self):
|
759 |
+
""" Returns true if expression has numeric data only. """
|
760 |
+
return not self.free_symbols
|
761 |
+
|
762 |
+
|
763 |
+
class HyperRep(Function):
|
764 |
+
"""
|
765 |
+
A base class for "hyper representation functions".
|
766 |
+
|
767 |
+
This is used exclusively in ``hyperexpand()``, but fits more logically here.
|
768 |
+
|
769 |
+
pFq is branched at 1 if p == q+1. For use with slater-expansion, we want
|
770 |
+
define an "analytic continuation" to all polar numbers, which is
|
771 |
+
continuous on circles and on the ray t*exp_polar(I*pi). Moreover, we want
|
772 |
+
a "nice" expression for the various cases.
|
773 |
+
|
774 |
+
This base class contains the core logic, concrete derived classes only
|
775 |
+
supply the actual functions.
|
776 |
+
|
777 |
+
"""
|
778 |
+
|
779 |
+
|
780 |
+
@classmethod
|
781 |
+
def eval(cls, *args):
|
782 |
+
newargs = tuple(map(unpolarify, args[:-1])) + args[-1:]
|
783 |
+
if args != newargs:
|
784 |
+
return cls(*newargs)
|
785 |
+
|
786 |
+
@classmethod
|
787 |
+
def _expr_small(cls, x):
|
788 |
+
""" An expression for F(x) which holds for |x| < 1. """
|
789 |
+
raise NotImplementedError
|
790 |
+
|
791 |
+
@classmethod
|
792 |
+
def _expr_small_minus(cls, x):
|
793 |
+
""" An expression for F(-x) which holds for |x| < 1. """
|
794 |
+
raise NotImplementedError
|
795 |
+
|
796 |
+
@classmethod
|
797 |
+
def _expr_big(cls, x, n):
|
798 |
+
""" An expression for F(exp_polar(2*I*pi*n)*x), |x| > 1. """
|
799 |
+
raise NotImplementedError
|
800 |
+
|
801 |
+
@classmethod
|
802 |
+
def _expr_big_minus(cls, x, n):
|
803 |
+
""" An expression for F(exp_polar(2*I*pi*n + pi*I)*x), |x| > 1. """
|
804 |
+
raise NotImplementedError
|
805 |
+
|
806 |
+
def _eval_rewrite_as_nonrep(self, *args, **kwargs):
|
807 |
+
x, n = self.args[-1].extract_branch_factor(allow_half=True)
|
808 |
+
minus = False
|
809 |
+
newargs = self.args[:-1] + (x,)
|
810 |
+
if not n.is_Integer:
|
811 |
+
minus = True
|
812 |
+
n -= S.Half
|
813 |
+
newerargs = newargs + (n,)
|
814 |
+
if minus:
|
815 |
+
small = self._expr_small_minus(*newargs)
|
816 |
+
big = self._expr_big_minus(*newerargs)
|
817 |
+
else:
|
818 |
+
small = self._expr_small(*newargs)
|
819 |
+
big = self._expr_big(*newerargs)
|
820 |
+
|
821 |
+
if big == small:
|
822 |
+
return small
|
823 |
+
return Piecewise((big, abs(x) > 1), (small, True))
|
824 |
+
|
825 |
+
def _eval_rewrite_as_nonrepsmall(self, *args, **kwargs):
|
826 |
+
x, n = self.args[-1].extract_branch_factor(allow_half=True)
|
827 |
+
args = self.args[:-1] + (x,)
|
828 |
+
if not n.is_Integer:
|
829 |
+
return self._expr_small_minus(*args)
|
830 |
+
return self._expr_small(*args)
|
831 |
+
|
832 |
+
|
833 |
+
class HyperRep_power1(HyperRep):
|
834 |
+
""" Return a representative for hyper([-a], [], z) == (1 - z)**a. """
|
835 |
+
|
836 |
+
@classmethod
|
837 |
+
def _expr_small(cls, a, x):
|
838 |
+
return (1 - x)**a
|
839 |
+
|
840 |
+
@classmethod
|
841 |
+
def _expr_small_minus(cls, a, x):
|
842 |
+
return (1 + x)**a
|
843 |
+
|
844 |
+
@classmethod
|
845 |
+
def _expr_big(cls, a, x, n):
|
846 |
+
if a.is_integer:
|
847 |
+
return cls._expr_small(a, x)
|
848 |
+
return (x - 1)**a*exp((2*n - 1)*pi*I*a)
|
849 |
+
|
850 |
+
@classmethod
|
851 |
+
def _expr_big_minus(cls, a, x, n):
|
852 |
+
if a.is_integer:
|
853 |
+
return cls._expr_small_minus(a, x)
|
854 |
+
return (1 + x)**a*exp(2*n*pi*I*a)
|
855 |
+
|
856 |
+
|
857 |
+
class HyperRep_power2(HyperRep):
|
858 |
+
""" Return a representative for hyper([a, a - 1/2], [2*a], z). """
|
859 |
+
|
860 |
+
@classmethod
|
861 |
+
def _expr_small(cls, a, x):
|
862 |
+
return 2**(2*a - 1)*(1 + sqrt(1 - x))**(1 - 2*a)
|
863 |
+
|
864 |
+
@classmethod
|
865 |
+
def _expr_small_minus(cls, a, x):
|
866 |
+
return 2**(2*a - 1)*(1 + sqrt(1 + x))**(1 - 2*a)
|
867 |
+
|
868 |
+
@classmethod
|
869 |
+
def _expr_big(cls, a, x, n):
|
870 |
+
sgn = -1
|
871 |
+
if n.is_odd:
|
872 |
+
sgn = 1
|
873 |
+
n -= 1
|
874 |
+
return 2**(2*a - 1)*(1 + sgn*I*sqrt(x - 1))**(1 - 2*a) \
|
875 |
+
*exp(-2*n*pi*I*a)
|
876 |
+
|
877 |
+
@classmethod
|
878 |
+
def _expr_big_minus(cls, a, x, n):
|
879 |
+
sgn = 1
|
880 |
+
if n.is_odd:
|
881 |
+
sgn = -1
|
882 |
+
return sgn*2**(2*a - 1)*(sqrt(1 + x) + sgn)**(1 - 2*a)*exp(-2*pi*I*a*n)
|
883 |
+
|
884 |
+
|
885 |
+
class HyperRep_log1(HyperRep):
|
886 |
+
""" Represent -z*hyper([1, 1], [2], z) == log(1 - z). """
|
887 |
+
@classmethod
|
888 |
+
def _expr_small(cls, x):
|
889 |
+
return log(1 - x)
|
890 |
+
|
891 |
+
@classmethod
|
892 |
+
def _expr_small_minus(cls, x):
|
893 |
+
return log(1 + x)
|
894 |
+
|
895 |
+
@classmethod
|
896 |
+
def _expr_big(cls, x, n):
|
897 |
+
return log(x - 1) + (2*n - 1)*pi*I
|
898 |
+
|
899 |
+
@classmethod
|
900 |
+
def _expr_big_minus(cls, x, n):
|
901 |
+
return log(1 + x) + 2*n*pi*I
|
902 |
+
|
903 |
+
|
904 |
+
class HyperRep_atanh(HyperRep):
|
905 |
+
""" Represent hyper([1/2, 1], [3/2], z) == atanh(sqrt(z))/sqrt(z). """
|
906 |
+
@classmethod
|
907 |
+
def _expr_small(cls, x):
|
908 |
+
return atanh(sqrt(x))/sqrt(x)
|
909 |
+
|
910 |
+
def _expr_small_minus(cls, x):
|
911 |
+
return atan(sqrt(x))/sqrt(x)
|
912 |
+
|
913 |
+
def _expr_big(cls, x, n):
|
914 |
+
if n.is_even:
|
915 |
+
return (acoth(sqrt(x)) + I*pi/2)/sqrt(x)
|
916 |
+
else:
|
917 |
+
return (acoth(sqrt(x)) - I*pi/2)/sqrt(x)
|
918 |
+
|
919 |
+
def _expr_big_minus(cls, x, n):
|
920 |
+
if n.is_even:
|
921 |
+
return atan(sqrt(x))/sqrt(x)
|
922 |
+
else:
|
923 |
+
return (atan(sqrt(x)) - pi)/sqrt(x)
|
924 |
+
|
925 |
+
|
926 |
+
class HyperRep_asin1(HyperRep):
|
927 |
+
""" Represent hyper([1/2, 1/2], [3/2], z) == asin(sqrt(z))/sqrt(z). """
|
928 |
+
@classmethod
|
929 |
+
def _expr_small(cls, z):
|
930 |
+
return asin(sqrt(z))/sqrt(z)
|
931 |
+
|
932 |
+
@classmethod
|
933 |
+
def _expr_small_minus(cls, z):
|
934 |
+
return asinh(sqrt(z))/sqrt(z)
|
935 |
+
|
936 |
+
@classmethod
|
937 |
+
def _expr_big(cls, z, n):
|
938 |
+
return S.NegativeOne**n*((S.Half - n)*pi/sqrt(z) + I*acosh(sqrt(z))/sqrt(z))
|
939 |
+
|
940 |
+
@classmethod
|
941 |
+
def _expr_big_minus(cls, z, n):
|
942 |
+
return S.NegativeOne**n*(asinh(sqrt(z))/sqrt(z) + n*pi*I/sqrt(z))
|
943 |
+
|
944 |
+
|
945 |
+
class HyperRep_asin2(HyperRep):
|
946 |
+
""" Represent hyper([1, 1], [3/2], z) == asin(sqrt(z))/sqrt(z)/sqrt(1-z). """
|
947 |
+
# TODO this can be nicer
|
948 |
+
@classmethod
|
949 |
+
def _expr_small(cls, z):
|
950 |
+
return HyperRep_asin1._expr_small(z) \
|
951 |
+
/HyperRep_power1._expr_small(S.Half, z)
|
952 |
+
|
953 |
+
@classmethod
|
954 |
+
def _expr_small_minus(cls, z):
|
955 |
+
return HyperRep_asin1._expr_small_minus(z) \
|
956 |
+
/HyperRep_power1._expr_small_minus(S.Half, z)
|
957 |
+
|
958 |
+
@classmethod
|
959 |
+
def _expr_big(cls, z, n):
|
960 |
+
return HyperRep_asin1._expr_big(z, n) \
|
961 |
+
/HyperRep_power1._expr_big(S.Half, z, n)
|
962 |
+
|
963 |
+
@classmethod
|
964 |
+
def _expr_big_minus(cls, z, n):
|
965 |
+
return HyperRep_asin1._expr_big_minus(z, n) \
|
966 |
+
/HyperRep_power1._expr_big_minus(S.Half, z, n)
|
967 |
+
|
968 |
+
|
969 |
+
class HyperRep_sqrts1(HyperRep):
|
970 |
+
""" Return a representative for hyper([-a, 1/2 - a], [1/2], z). """
|
971 |
+
|
972 |
+
@classmethod
|
973 |
+
def _expr_small(cls, a, z):
|
974 |
+
return ((1 - sqrt(z))**(2*a) + (1 + sqrt(z))**(2*a))/2
|
975 |
+
|
976 |
+
@classmethod
|
977 |
+
def _expr_small_minus(cls, a, z):
|
978 |
+
return (1 + z)**a*cos(2*a*atan(sqrt(z)))
|
979 |
+
|
980 |
+
@classmethod
|
981 |
+
def _expr_big(cls, a, z, n):
|
982 |
+
if n.is_even:
|
983 |
+
return ((sqrt(z) + 1)**(2*a)*exp(2*pi*I*n*a) +
|
984 |
+
(sqrt(z) - 1)**(2*a)*exp(2*pi*I*(n - 1)*a))/2
|
985 |
+
else:
|
986 |
+
n -= 1
|
987 |
+
return ((sqrt(z) - 1)**(2*a)*exp(2*pi*I*a*(n + 1)) +
|
988 |
+
(sqrt(z) + 1)**(2*a)*exp(2*pi*I*a*n))/2
|
989 |
+
|
990 |
+
@classmethod
|
991 |
+
def _expr_big_minus(cls, a, z, n):
|
992 |
+
if n.is_even:
|
993 |
+
return (1 + z)**a*exp(2*pi*I*n*a)*cos(2*a*atan(sqrt(z)))
|
994 |
+
else:
|
995 |
+
return (1 + z)**a*exp(2*pi*I*n*a)*cos(2*a*atan(sqrt(z)) - 2*pi*a)
|
996 |
+
|
997 |
+
|
998 |
+
class HyperRep_sqrts2(HyperRep):
|
999 |
+
""" Return a representative for
|
1000 |
+
sqrt(z)/2*[(1-sqrt(z))**2a - (1 + sqrt(z))**2a]
|
1001 |
+
== -2*z/(2*a+1) d/dz hyper([-a - 1/2, -a], [1/2], z)"""
|
1002 |
+
|
1003 |
+
@classmethod
|
1004 |
+
def _expr_small(cls, a, z):
|
1005 |
+
return sqrt(z)*((1 - sqrt(z))**(2*a) - (1 + sqrt(z))**(2*a))/2
|
1006 |
+
|
1007 |
+
@classmethod
|
1008 |
+
def _expr_small_minus(cls, a, z):
|
1009 |
+
return sqrt(z)*(1 + z)**a*sin(2*a*atan(sqrt(z)))
|
1010 |
+
|
1011 |
+
@classmethod
|
1012 |
+
def _expr_big(cls, a, z, n):
|
1013 |
+
if n.is_even:
|
1014 |
+
return sqrt(z)/2*((sqrt(z) - 1)**(2*a)*exp(2*pi*I*a*(n - 1)) -
|
1015 |
+
(sqrt(z) + 1)**(2*a)*exp(2*pi*I*a*n))
|
1016 |
+
else:
|
1017 |
+
n -= 1
|
1018 |
+
return sqrt(z)/2*((sqrt(z) - 1)**(2*a)*exp(2*pi*I*a*(n + 1)) -
|
1019 |
+
(sqrt(z) + 1)**(2*a)*exp(2*pi*I*a*n))
|
1020 |
+
|
1021 |
+
def _expr_big_minus(cls, a, z, n):
|
1022 |
+
if n.is_even:
|
1023 |
+
return (1 + z)**a*exp(2*pi*I*n*a)*sqrt(z)*sin(2*a*atan(sqrt(z)))
|
1024 |
+
else:
|
1025 |
+
return (1 + z)**a*exp(2*pi*I*n*a)*sqrt(z) \
|
1026 |
+
*sin(2*a*atan(sqrt(z)) - 2*pi*a)
|
1027 |
+
|
1028 |
+
|
1029 |
+
class HyperRep_log2(HyperRep):
|
1030 |
+
""" Represent log(1/2 + sqrt(1 - z)/2) == -z/4*hyper([3/2, 1, 1], [2, 2], z) """
|
1031 |
+
|
1032 |
+
@classmethod
|
1033 |
+
def _expr_small(cls, z):
|
1034 |
+
return log(S.Half + sqrt(1 - z)/2)
|
1035 |
+
|
1036 |
+
@classmethod
|
1037 |
+
def _expr_small_minus(cls, z):
|
1038 |
+
return log(S.Half + sqrt(1 + z)/2)
|
1039 |
+
|
1040 |
+
@classmethod
|
1041 |
+
def _expr_big(cls, z, n):
|
1042 |
+
if n.is_even:
|
1043 |
+
return (n - S.Half)*pi*I + log(sqrt(z)/2) + I*asin(1/sqrt(z))
|
1044 |
+
else:
|
1045 |
+
return (n - S.Half)*pi*I + log(sqrt(z)/2) - I*asin(1/sqrt(z))
|
1046 |
+
|
1047 |
+
def _expr_big_minus(cls, z, n):
|
1048 |
+
if n.is_even:
|
1049 |
+
return pi*I*n + log(S.Half + sqrt(1 + z)/2)
|
1050 |
+
else:
|
1051 |
+
return pi*I*n + log(sqrt(1 + z)/2 - S.Half)
|
1052 |
+
|
1053 |
+
|
1054 |
+
class HyperRep_cosasin(HyperRep):
|
1055 |
+
""" Represent hyper([a, -a], [1/2], z) == cos(2*a*asin(sqrt(z))). """
|
1056 |
+
# Note there are many alternative expressions, e.g. as powers of a sum of
|
1057 |
+
# square roots.
|
1058 |
+
|
1059 |
+
@classmethod
|
1060 |
+
def _expr_small(cls, a, z):
|
1061 |
+
return cos(2*a*asin(sqrt(z)))
|
1062 |
+
|
1063 |
+
@classmethod
|
1064 |
+
def _expr_small_minus(cls, a, z):
|
1065 |
+
return cosh(2*a*asinh(sqrt(z)))
|
1066 |
+
|
1067 |
+
@classmethod
|
1068 |
+
def _expr_big(cls, a, z, n):
|
1069 |
+
return cosh(2*a*acosh(sqrt(z)) + a*pi*I*(2*n - 1))
|
1070 |
+
|
1071 |
+
@classmethod
|
1072 |
+
def _expr_big_minus(cls, a, z, n):
|
1073 |
+
return cosh(2*a*asinh(sqrt(z)) + 2*a*pi*I*n)
|
1074 |
+
|
1075 |
+
|
1076 |
+
class HyperRep_sinasin(HyperRep):
|
1077 |
+
""" Represent 2*a*z*hyper([1 - a, 1 + a], [3/2], z)
|
1078 |
+
== sqrt(z)/sqrt(1-z)*sin(2*a*asin(sqrt(z))) """
|
1079 |
+
|
1080 |
+
@classmethod
|
1081 |
+
def _expr_small(cls, a, z):
|
1082 |
+
return sqrt(z)/sqrt(1 - z)*sin(2*a*asin(sqrt(z)))
|
1083 |
+
|
1084 |
+
@classmethod
|
1085 |
+
def _expr_small_minus(cls, a, z):
|
1086 |
+
return -sqrt(z)/sqrt(1 + z)*sinh(2*a*asinh(sqrt(z)))
|
1087 |
+
|
1088 |
+
@classmethod
|
1089 |
+
def _expr_big(cls, a, z, n):
|
1090 |
+
return -1/sqrt(1 - 1/z)*sinh(2*a*acosh(sqrt(z)) + a*pi*I*(2*n - 1))
|
1091 |
+
|
1092 |
+
@classmethod
|
1093 |
+
def _expr_big_minus(cls, a, z, n):
|
1094 |
+
return -1/sqrt(1 + 1/z)*sinh(2*a*asinh(sqrt(z)) + 2*a*pi*I*n)
|
1095 |
+
|
1096 |
+
class appellf1(Function):
|
1097 |
+
r"""
|
1098 |
+
This is the Appell hypergeometric function of two variables as:
|
1099 |
+
|
1100 |
+
.. math ::
|
1101 |
+
F_1(a,b_1,b_2,c,x,y) = \sum_{m=0}^{\infty} \sum_{n=0}^{\infty}
|
1102 |
+
\frac{(a)_{m+n} (b_1)_m (b_2)_n}{(c)_{m+n}}
|
1103 |
+
\frac{x^m y^n}{m! n!}.
|
1104 |
+
|
1105 |
+
Examples
|
1106 |
+
========
|
1107 |
+
|
1108 |
+
>>> from sympy import appellf1, symbols
|
1109 |
+
>>> x, y, a, b1, b2, c = symbols('x y a b1 b2 c')
|
1110 |
+
>>> appellf1(2., 1., 6., 4., 5., 6.)
|
1111 |
+
0.0063339426292673
|
1112 |
+
>>> appellf1(12., 12., 6., 4., 0.5, 0.12)
|
1113 |
+
172870711.659936
|
1114 |
+
>>> appellf1(40, 2, 6, 4, 15, 60)
|
1115 |
+
appellf1(40, 2, 6, 4, 15, 60)
|
1116 |
+
>>> appellf1(20., 12., 10., 3., 0.5, 0.12)
|
1117 |
+
15605338197184.4
|
1118 |
+
>>> appellf1(40, 2, 6, 4, x, y)
|
1119 |
+
appellf1(40, 2, 6, 4, x, y)
|
1120 |
+
>>> appellf1(a, b1, b2, c, x, y)
|
1121 |
+
appellf1(a, b1, b2, c, x, y)
|
1122 |
+
|
1123 |
+
References
|
1124 |
+
==========
|
1125 |
+
|
1126 |
+
.. [1] https://en.wikipedia.org/wiki/Appell_series
|
1127 |
+
.. [2] https://functions.wolfram.com/HypergeometricFunctions/AppellF1/
|
1128 |
+
|
1129 |
+
"""
|
1130 |
+
|
1131 |
+
@classmethod
|
1132 |
+
def eval(cls, a, b1, b2, c, x, y):
|
1133 |
+
if default_sort_key(b1) > default_sort_key(b2):
|
1134 |
+
b1, b2 = b2, b1
|
1135 |
+
x, y = y, x
|
1136 |
+
return cls(a, b1, b2, c, x, y)
|
1137 |
+
elif b1 == b2 and default_sort_key(x) > default_sort_key(y):
|
1138 |
+
x, y = y, x
|
1139 |
+
return cls(a, b1, b2, c, x, y)
|
1140 |
+
if x == 0 and y == 0:
|
1141 |
+
return S.One
|
1142 |
+
|
1143 |
+
def fdiff(self, argindex=5):
|
1144 |
+
a, b1, b2, c, x, y = self.args
|
1145 |
+
if argindex == 5:
|
1146 |
+
return (a*b1/c)*appellf1(a + 1, b1 + 1, b2, c + 1, x, y)
|
1147 |
+
elif argindex == 6:
|
1148 |
+
return (a*b2/c)*appellf1(a + 1, b1, b2 + 1, c + 1, x, y)
|
1149 |
+
elif argindex in (1, 2, 3, 4):
|
1150 |
+
return Derivative(self, self.args[argindex-1])
|
1151 |
+
else:
|
1152 |
+
raise ArgumentIndexError(self, argindex)
|
venv/lib/python3.10/site-packages/sympy/functions/special/mathieu_functions.py
ADDED
@@ -0,0 +1,269 @@
|
|
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|
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|
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|
|
|
|
|
|
|
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|
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|
|
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|
|
|
|
|
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|
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|
|
|
|
|
|
|
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|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
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|
|
|
|
|
|
|
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|
|
|
|
|
|
|
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|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
1 |
+
""" This module contains the Mathieu functions.
|
2 |
+
"""
|
3 |
+
|
4 |
+
from sympy.core.function import Function, ArgumentIndexError
|
5 |
+
from sympy.functions.elementary.miscellaneous import sqrt
|
6 |
+
from sympy.functions.elementary.trigonometric import sin, cos
|
7 |
+
|
8 |
+
|
9 |
+
class MathieuBase(Function):
|
10 |
+
"""
|
11 |
+
Abstract base class for Mathieu functions.
|
12 |
+
|
13 |
+
This class is meant to reduce code duplication.
|
14 |
+
|
15 |
+
"""
|
16 |
+
|
17 |
+
unbranched = True
|
18 |
+
|
19 |
+
def _eval_conjugate(self):
|
20 |
+
a, q, z = self.args
|
21 |
+
return self.func(a.conjugate(), q.conjugate(), z.conjugate())
|
22 |
+
|
23 |
+
|
24 |
+
class mathieus(MathieuBase):
|
25 |
+
r"""
|
26 |
+
The Mathieu Sine function $S(a,q,z)$.
|
27 |
+
|
28 |
+
Explanation
|
29 |
+
===========
|
30 |
+
|
31 |
+
This function is one solution of the Mathieu differential equation:
|
32 |
+
|
33 |
+
.. math ::
|
34 |
+
y(x)^{\prime\prime} + (a - 2 q \cos(2 x)) y(x) = 0
|
35 |
+
|
36 |
+
The other solution is the Mathieu Cosine function.
|
37 |
+
|
38 |
+
Examples
|
39 |
+
========
|
40 |
+
|
41 |
+
>>> from sympy import diff, mathieus
|
42 |
+
>>> from sympy.abc import a, q, z
|
43 |
+
|
44 |
+
>>> mathieus(a, q, z)
|
45 |
+
mathieus(a, q, z)
|
46 |
+
|
47 |
+
>>> mathieus(a, 0, z)
|
48 |
+
sin(sqrt(a)*z)
|
49 |
+
|
50 |
+
>>> diff(mathieus(a, q, z), z)
|
51 |
+
mathieusprime(a, q, z)
|
52 |
+
|
53 |
+
See Also
|
54 |
+
========
|
55 |
+
|
56 |
+
mathieuc: Mathieu cosine function.
|
57 |
+
mathieusprime: Derivative of Mathieu sine function.
|
58 |
+
mathieucprime: Derivative of Mathieu cosine function.
|
59 |
+
|
60 |
+
References
|
61 |
+
==========
|
62 |
+
|
63 |
+
.. [1] https://en.wikipedia.org/wiki/Mathieu_function
|
64 |
+
.. [2] https://dlmf.nist.gov/28
|
65 |
+
.. [3] https://mathworld.wolfram.com/MathieuFunction.html
|
66 |
+
.. [4] https://functions.wolfram.com/MathieuandSpheroidalFunctions/MathieuS/
|
67 |
+
|
68 |
+
"""
|
69 |
+
|
70 |
+
def fdiff(self, argindex=1):
|
71 |
+
if argindex == 3:
|
72 |
+
a, q, z = self.args
|
73 |
+
return mathieusprime(a, q, z)
|
74 |
+
else:
|
75 |
+
raise ArgumentIndexError(self, argindex)
|
76 |
+
|
77 |
+
@classmethod
|
78 |
+
def eval(cls, a, q, z):
|
79 |
+
if q.is_Number and q.is_zero:
|
80 |
+
return sin(sqrt(a)*z)
|
81 |
+
# Try to pull out factors of -1
|
82 |
+
if z.could_extract_minus_sign():
|
83 |
+
return -cls(a, q, -z)
|
84 |
+
|
85 |
+
|
86 |
+
class mathieuc(MathieuBase):
|
87 |
+
r"""
|
88 |
+
The Mathieu Cosine function $C(a,q,z)$.
|
89 |
+
|
90 |
+
Explanation
|
91 |
+
===========
|
92 |
+
|
93 |
+
This function is one solution of the Mathieu differential equation:
|
94 |
+
|
95 |
+
.. math ::
|
96 |
+
y(x)^{\prime\prime} + (a - 2 q \cos(2 x)) y(x) = 0
|
97 |
+
|
98 |
+
The other solution is the Mathieu Sine function.
|
99 |
+
|
100 |
+
Examples
|
101 |
+
========
|
102 |
+
|
103 |
+
>>> from sympy import diff, mathieuc
|
104 |
+
>>> from sympy.abc import a, q, z
|
105 |
+
|
106 |
+
>>> mathieuc(a, q, z)
|
107 |
+
mathieuc(a, q, z)
|
108 |
+
|
109 |
+
>>> mathieuc(a, 0, z)
|
110 |
+
cos(sqrt(a)*z)
|
111 |
+
|
112 |
+
>>> diff(mathieuc(a, q, z), z)
|
113 |
+
mathieucprime(a, q, z)
|
114 |
+
|
115 |
+
See Also
|
116 |
+
========
|
117 |
+
|
118 |
+
mathieus: Mathieu sine function
|
119 |
+
mathieusprime: Derivative of Mathieu sine function
|
120 |
+
mathieucprime: Derivative of Mathieu cosine function
|
121 |
+
|
122 |
+
References
|
123 |
+
==========
|
124 |
+
|
125 |
+
.. [1] https://en.wikipedia.org/wiki/Mathieu_function
|
126 |
+
.. [2] https://dlmf.nist.gov/28
|
127 |
+
.. [3] https://mathworld.wolfram.com/MathieuFunction.html
|
128 |
+
.. [4] https://functions.wolfram.com/MathieuandSpheroidalFunctions/MathieuC/
|
129 |
+
|
130 |
+
"""
|
131 |
+
|
132 |
+
def fdiff(self, argindex=1):
|
133 |
+
if argindex == 3:
|
134 |
+
a, q, z = self.args
|
135 |
+
return mathieucprime(a, q, z)
|
136 |
+
else:
|
137 |
+
raise ArgumentIndexError(self, argindex)
|
138 |
+
|
139 |
+
@classmethod
|
140 |
+
def eval(cls, a, q, z):
|
141 |
+
if q.is_Number and q.is_zero:
|
142 |
+
return cos(sqrt(a)*z)
|
143 |
+
# Try to pull out factors of -1
|
144 |
+
if z.could_extract_minus_sign():
|
145 |
+
return cls(a, q, -z)
|
146 |
+
|
147 |
+
|
148 |
+
class mathieusprime(MathieuBase):
|
149 |
+
r"""
|
150 |
+
The derivative $S^{\prime}(a,q,z)$ of the Mathieu Sine function.
|
151 |
+
|
152 |
+
Explanation
|
153 |
+
===========
|
154 |
+
|
155 |
+
This function is one solution of the Mathieu differential equation:
|
156 |
+
|
157 |
+
.. math ::
|
158 |
+
y(x)^{\prime\prime} + (a - 2 q \cos(2 x)) y(x) = 0
|
159 |
+
|
160 |
+
The other solution is the Mathieu Cosine function.
|
161 |
+
|
162 |
+
Examples
|
163 |
+
========
|
164 |
+
|
165 |
+
>>> from sympy import diff, mathieusprime
|
166 |
+
>>> from sympy.abc import a, q, z
|
167 |
+
|
168 |
+
>>> mathieusprime(a, q, z)
|
169 |
+
mathieusprime(a, q, z)
|
170 |
+
|
171 |
+
>>> mathieusprime(a, 0, z)
|
172 |
+
sqrt(a)*cos(sqrt(a)*z)
|
173 |
+
|
174 |
+
>>> diff(mathieusprime(a, q, z), z)
|
175 |
+
(-a + 2*q*cos(2*z))*mathieus(a, q, z)
|
176 |
+
|
177 |
+
See Also
|
178 |
+
========
|
179 |
+
|
180 |
+
mathieus: Mathieu sine function
|
181 |
+
mathieuc: Mathieu cosine function
|
182 |
+
mathieucprime: Derivative of Mathieu cosine function
|
183 |
+
|
184 |
+
References
|
185 |
+
==========
|
186 |
+
|
187 |
+
.. [1] https://en.wikipedia.org/wiki/Mathieu_function
|
188 |
+
.. [2] https://dlmf.nist.gov/28
|
189 |
+
.. [3] https://mathworld.wolfram.com/MathieuFunction.html
|
190 |
+
.. [4] https://functions.wolfram.com/MathieuandSpheroidalFunctions/MathieuSPrime/
|
191 |
+
|
192 |
+
"""
|
193 |
+
|
194 |
+
def fdiff(self, argindex=1):
|
195 |
+
if argindex == 3:
|
196 |
+
a, q, z = self.args
|
197 |
+
return (2*q*cos(2*z) - a)*mathieus(a, q, z)
|
198 |
+
else:
|
199 |
+
raise ArgumentIndexError(self, argindex)
|
200 |
+
|
201 |
+
@classmethod
|
202 |
+
def eval(cls, a, q, z):
|
203 |
+
if q.is_Number and q.is_zero:
|
204 |
+
return sqrt(a)*cos(sqrt(a)*z)
|
205 |
+
# Try to pull out factors of -1
|
206 |
+
if z.could_extract_minus_sign():
|
207 |
+
return cls(a, q, -z)
|
208 |
+
|
209 |
+
|
210 |
+
class mathieucprime(MathieuBase):
|
211 |
+
r"""
|
212 |
+
The derivative $C^{\prime}(a,q,z)$ of the Mathieu Cosine function.
|
213 |
+
|
214 |
+
Explanation
|
215 |
+
===========
|
216 |
+
|
217 |
+
This function is one solution of the Mathieu differential equation:
|
218 |
+
|
219 |
+
.. math ::
|
220 |
+
y(x)^{\prime\prime} + (a - 2 q \cos(2 x)) y(x) = 0
|
221 |
+
|
222 |
+
The other solution is the Mathieu Sine function.
|
223 |
+
|
224 |
+
Examples
|
225 |
+
========
|
226 |
+
|
227 |
+
>>> from sympy import diff, mathieucprime
|
228 |
+
>>> from sympy.abc import a, q, z
|
229 |
+
|
230 |
+
>>> mathieucprime(a, q, z)
|
231 |
+
mathieucprime(a, q, z)
|
232 |
+
|
233 |
+
>>> mathieucprime(a, 0, z)
|
234 |
+
-sqrt(a)*sin(sqrt(a)*z)
|
235 |
+
|
236 |
+
>>> diff(mathieucprime(a, q, z), z)
|
237 |
+
(-a + 2*q*cos(2*z))*mathieuc(a, q, z)
|
238 |
+
|
239 |
+
See Also
|
240 |
+
========
|
241 |
+
|
242 |
+
mathieus: Mathieu sine function
|
243 |
+
mathieuc: Mathieu cosine function
|
244 |
+
mathieusprime: Derivative of Mathieu sine function
|
245 |
+
|
246 |
+
References
|
247 |
+
==========
|
248 |
+
|
249 |
+
.. [1] https://en.wikipedia.org/wiki/Mathieu_function
|
250 |
+
.. [2] https://dlmf.nist.gov/28
|
251 |
+
.. [3] https://mathworld.wolfram.com/MathieuFunction.html
|
252 |
+
.. [4] https://functions.wolfram.com/MathieuandSpheroidalFunctions/MathieuCPrime/
|
253 |
+
|
254 |
+
"""
|
255 |
+
|
256 |
+
def fdiff(self, argindex=1):
|
257 |
+
if argindex == 3:
|
258 |
+
a, q, z = self.args
|
259 |
+
return (2*q*cos(2*z) - a)*mathieuc(a, q, z)
|
260 |
+
else:
|
261 |
+
raise ArgumentIndexError(self, argindex)
|
262 |
+
|
263 |
+
@classmethod
|
264 |
+
def eval(cls, a, q, z):
|
265 |
+
if q.is_Number and q.is_zero:
|
266 |
+
return -sqrt(a)*sin(sqrt(a)*z)
|
267 |
+
# Try to pull out factors of -1
|
268 |
+
if z.could_extract_minus_sign():
|
269 |
+
return -cls(a, q, -z)
|
venv/lib/python3.10/site-packages/sympy/functions/special/polynomials.py
ADDED
@@ -0,0 +1,1447 @@
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|
1 |
+
"""
|
2 |
+
This module mainly implements special orthogonal polynomials.
|
3 |
+
|
4 |
+
See also functions.combinatorial.numbers which contains some
|
5 |
+
combinatorial polynomials.
|
6 |
+
|
7 |
+
"""
|
8 |
+
|
9 |
+
from sympy.core import Rational
|
10 |
+
from sympy.core.function import Function, ArgumentIndexError
|
11 |
+
from sympy.core.singleton import S
|
12 |
+
from sympy.core.symbol import Dummy
|
13 |
+
from sympy.functions.combinatorial.factorials import binomial, factorial, RisingFactorial
|
14 |
+
from sympy.functions.elementary.complexes import re
|
15 |
+
from sympy.functions.elementary.exponential import exp
|
16 |
+
from sympy.functions.elementary.integers import floor
|
17 |
+
from sympy.functions.elementary.miscellaneous import sqrt
|
18 |
+
from sympy.functions.elementary.trigonometric import cos, sec
|
19 |
+
from sympy.functions.special.gamma_functions import gamma
|
20 |
+
from sympy.functions.special.hyper import hyper
|
21 |
+
from sympy.polys.orthopolys import (chebyshevt_poly, chebyshevu_poly,
|
22 |
+
gegenbauer_poly, hermite_poly, hermite_prob_poly,
|
23 |
+
jacobi_poly, laguerre_poly, legendre_poly)
|
24 |
+
|
25 |
+
_x = Dummy('x')
|
26 |
+
|
27 |
+
|
28 |
+
class OrthogonalPolynomial(Function):
|
29 |
+
"""Base class for orthogonal polynomials.
|
30 |
+
"""
|
31 |
+
|
32 |
+
@classmethod
|
33 |
+
def _eval_at_order(cls, n, x):
|
34 |
+
if n.is_integer and n >= 0:
|
35 |
+
return cls._ortho_poly(int(n), _x).subs(_x, x)
|
36 |
+
|
37 |
+
def _eval_conjugate(self):
|
38 |
+
return self.func(self.args[0], self.args[1].conjugate())
|
39 |
+
|
40 |
+
#----------------------------------------------------------------------------
|
41 |
+
# Jacobi polynomials
|
42 |
+
#
|
43 |
+
|
44 |
+
|
45 |
+
class jacobi(OrthogonalPolynomial):
|
46 |
+
r"""
|
47 |
+
Jacobi polynomial $P_n^{\left(\alpha, \beta\right)}(x)$.
|
48 |
+
|
49 |
+
Explanation
|
50 |
+
===========
|
51 |
+
|
52 |
+
``jacobi(n, alpha, beta, x)`` gives the $n$th Jacobi polynomial
|
53 |
+
in $x$, $P_n^{\left(\alpha, \beta\right)}(x)$.
|
54 |
+
|
55 |
+
The Jacobi polynomials are orthogonal on $[-1, 1]$ with respect
|
56 |
+
to the weight $\left(1-x\right)^\alpha \left(1+x\right)^\beta$.
|
57 |
+
|
58 |
+
Examples
|
59 |
+
========
|
60 |
+
|
61 |
+
>>> from sympy import jacobi, S, conjugate, diff
|
62 |
+
>>> from sympy.abc import a, b, n, x
|
63 |
+
|
64 |
+
>>> jacobi(0, a, b, x)
|
65 |
+
1
|
66 |
+
>>> jacobi(1, a, b, x)
|
67 |
+
a/2 - b/2 + x*(a/2 + b/2 + 1)
|
68 |
+
>>> jacobi(2, a, b, x)
|
69 |
+
a**2/8 - a*b/4 - a/8 + b**2/8 - b/8 + x**2*(a**2/8 + a*b/4 + 7*a/8 + b**2/8 + 7*b/8 + 3/2) + x*(a**2/4 + 3*a/4 - b**2/4 - 3*b/4) - 1/2
|
70 |
+
|
71 |
+
>>> jacobi(n, a, b, x)
|
72 |
+
jacobi(n, a, b, x)
|
73 |
+
|
74 |
+
>>> jacobi(n, a, a, x)
|
75 |
+
RisingFactorial(a + 1, n)*gegenbauer(n,
|
76 |
+
a + 1/2, x)/RisingFactorial(2*a + 1, n)
|
77 |
+
|
78 |
+
>>> jacobi(n, 0, 0, x)
|
79 |
+
legendre(n, x)
|
80 |
+
|
81 |
+
>>> jacobi(n, S(1)/2, S(1)/2, x)
|
82 |
+
RisingFactorial(3/2, n)*chebyshevu(n, x)/factorial(n + 1)
|
83 |
+
|
84 |
+
>>> jacobi(n, -S(1)/2, -S(1)/2, x)
|
85 |
+
RisingFactorial(1/2, n)*chebyshevt(n, x)/factorial(n)
|
86 |
+
|
87 |
+
>>> jacobi(n, a, b, -x)
|
88 |
+
(-1)**n*jacobi(n, b, a, x)
|
89 |
+
|
90 |
+
>>> jacobi(n, a, b, 0)
|
91 |
+
gamma(a + n + 1)*hyper((-b - n, -n), (a + 1,), -1)/(2**n*factorial(n)*gamma(a + 1))
|
92 |
+
>>> jacobi(n, a, b, 1)
|
93 |
+
RisingFactorial(a + 1, n)/factorial(n)
|
94 |
+
|
95 |
+
>>> conjugate(jacobi(n, a, b, x))
|
96 |
+
jacobi(n, conjugate(a), conjugate(b), conjugate(x))
|
97 |
+
|
98 |
+
>>> diff(jacobi(n,a,b,x), x)
|
99 |
+
(a/2 + b/2 + n/2 + 1/2)*jacobi(n - 1, a + 1, b + 1, x)
|
100 |
+
|
101 |
+
See Also
|
102 |
+
========
|
103 |
+
|
104 |
+
gegenbauer,
|
105 |
+
chebyshevt_root, chebyshevu, chebyshevu_root,
|
106 |
+
legendre, assoc_legendre,
|
107 |
+
hermite, hermite_prob,
|
108 |
+
laguerre, assoc_laguerre,
|
109 |
+
sympy.polys.orthopolys.jacobi_poly,
|
110 |
+
sympy.polys.orthopolys.gegenbauer_poly
|
111 |
+
sympy.polys.orthopolys.chebyshevt_poly
|
112 |
+
sympy.polys.orthopolys.chebyshevu_poly
|
113 |
+
sympy.polys.orthopolys.hermite_poly
|
114 |
+
sympy.polys.orthopolys.legendre_poly
|
115 |
+
sympy.polys.orthopolys.laguerre_poly
|
116 |
+
|
117 |
+
References
|
118 |
+
==========
|
119 |
+
|
120 |
+
.. [1] https://en.wikipedia.org/wiki/Jacobi_polynomials
|
121 |
+
.. [2] https://mathworld.wolfram.com/JacobiPolynomial.html
|
122 |
+
.. [3] https://functions.wolfram.com/Polynomials/JacobiP/
|
123 |
+
|
124 |
+
"""
|
125 |
+
|
126 |
+
@classmethod
|
127 |
+
def eval(cls, n, a, b, x):
|
128 |
+
# Simplify to other polynomials
|
129 |
+
# P^{a, a}_n(x)
|
130 |
+
if a == b:
|
131 |
+
if a == Rational(-1, 2):
|
132 |
+
return RisingFactorial(S.Half, n) / factorial(n) * chebyshevt(n, x)
|
133 |
+
elif a.is_zero:
|
134 |
+
return legendre(n, x)
|
135 |
+
elif a == S.Half:
|
136 |
+
return RisingFactorial(3*S.Half, n) / factorial(n + 1) * chebyshevu(n, x)
|
137 |
+
else:
|
138 |
+
return RisingFactorial(a + 1, n) / RisingFactorial(2*a + 1, n) * gegenbauer(n, a + S.Half, x)
|
139 |
+
elif b == -a:
|
140 |
+
# P^{a, -a}_n(x)
|
141 |
+
return gamma(n + a + 1) / gamma(n + 1) * (1 + x)**(a/2) / (1 - x)**(a/2) * assoc_legendre(n, -a, x)
|
142 |
+
|
143 |
+
if not n.is_Number:
|
144 |
+
# Symbolic result P^{a,b}_n(x)
|
145 |
+
# P^{a,b}_n(-x) ---> (-1)**n * P^{b,a}_n(-x)
|
146 |
+
if x.could_extract_minus_sign():
|
147 |
+
return S.NegativeOne**n * jacobi(n, b, a, -x)
|
148 |
+
# We can evaluate for some special values of x
|
149 |
+
if x.is_zero:
|
150 |
+
return (2**(-n) * gamma(a + n + 1) / (gamma(a + 1) * factorial(n)) *
|
151 |
+
hyper([-b - n, -n], [a + 1], -1))
|
152 |
+
if x == S.One:
|
153 |
+
return RisingFactorial(a + 1, n) / factorial(n)
|
154 |
+
elif x is S.Infinity:
|
155 |
+
if n.is_positive:
|
156 |
+
# Make sure a+b+2*n \notin Z
|
157 |
+
if (a + b + 2*n).is_integer:
|
158 |
+
raise ValueError("Error. a + b + 2*n should not be an integer.")
|
159 |
+
return RisingFactorial(a + b + n + 1, n) * S.Infinity
|
160 |
+
else:
|
161 |
+
# n is a given fixed integer, evaluate into polynomial
|
162 |
+
return jacobi_poly(n, a, b, x)
|
163 |
+
|
164 |
+
def fdiff(self, argindex=4):
|
165 |
+
from sympy.concrete.summations import Sum
|
166 |
+
if argindex == 1:
|
167 |
+
# Diff wrt n
|
168 |
+
raise ArgumentIndexError(self, argindex)
|
169 |
+
elif argindex == 2:
|
170 |
+
# Diff wrt a
|
171 |
+
n, a, b, x = self.args
|
172 |
+
k = Dummy("k")
|
173 |
+
f1 = 1 / (a + b + n + k + 1)
|
174 |
+
f2 = ((a + b + 2*k + 1) * RisingFactorial(b + k + 1, n - k) /
|
175 |
+
((n - k) * RisingFactorial(a + b + k + 1, n - k)))
|
176 |
+
return Sum(f1 * (jacobi(n, a, b, x) + f2*jacobi(k, a, b, x)), (k, 0, n - 1))
|
177 |
+
elif argindex == 3:
|
178 |
+
# Diff wrt b
|
179 |
+
n, a, b, x = self.args
|
180 |
+
k = Dummy("k")
|
181 |
+
f1 = 1 / (a + b + n + k + 1)
|
182 |
+
f2 = (-1)**(n - k) * ((a + b + 2*k + 1) * RisingFactorial(a + k + 1, n - k) /
|
183 |
+
((n - k) * RisingFactorial(a + b + k + 1, n - k)))
|
184 |
+
return Sum(f1 * (jacobi(n, a, b, x) + f2*jacobi(k, a, b, x)), (k, 0, n - 1))
|
185 |
+
elif argindex == 4:
|
186 |
+
# Diff wrt x
|
187 |
+
n, a, b, x = self.args
|
188 |
+
return S.Half * (a + b + n + 1) * jacobi(n - 1, a + 1, b + 1, x)
|
189 |
+
else:
|
190 |
+
raise ArgumentIndexError(self, argindex)
|
191 |
+
|
192 |
+
def _eval_rewrite_as_Sum(self, n, a, b, x, **kwargs):
|
193 |
+
from sympy.concrete.summations import Sum
|
194 |
+
# Make sure n \in N
|
195 |
+
if n.is_negative or n.is_integer is False:
|
196 |
+
raise ValueError("Error: n should be a non-negative integer.")
|
197 |
+
k = Dummy("k")
|
198 |
+
kern = (RisingFactorial(-n, k) * RisingFactorial(a + b + n + 1, k) * RisingFactorial(a + k + 1, n - k) /
|
199 |
+
factorial(k) * ((1 - x)/2)**k)
|
200 |
+
return 1 / factorial(n) * Sum(kern, (k, 0, n))
|
201 |
+
|
202 |
+
def _eval_rewrite_as_polynomial(self, n, a, b, x, **kwargs):
|
203 |
+
# This function is just kept for backwards compatibility
|
204 |
+
# but should not be used
|
205 |
+
return self._eval_rewrite_as_Sum(n, a, b, x, **kwargs)
|
206 |
+
|
207 |
+
def _eval_conjugate(self):
|
208 |
+
n, a, b, x = self.args
|
209 |
+
return self.func(n, a.conjugate(), b.conjugate(), x.conjugate())
|
210 |
+
|
211 |
+
|
212 |
+
def jacobi_normalized(n, a, b, x):
|
213 |
+
r"""
|
214 |
+
Jacobi polynomial $P_n^{\left(\alpha, \beta\right)}(x)$.
|
215 |
+
|
216 |
+
Explanation
|
217 |
+
===========
|
218 |
+
|
219 |
+
``jacobi_normalized(n, alpha, beta, x)`` gives the $n$th
|
220 |
+
Jacobi polynomial in $x$, $P_n^{\left(\alpha, \beta\right)}(x)$.
|
221 |
+
|
222 |
+
The Jacobi polynomials are orthogonal on $[-1, 1]$ with respect
|
223 |
+
to the weight $\left(1-x\right)^\alpha \left(1+x\right)^\beta$.
|
224 |
+
|
225 |
+
This functions returns the polynomials normilzed:
|
226 |
+
|
227 |
+
.. math::
|
228 |
+
|
229 |
+
\int_{-1}^{1}
|
230 |
+
P_m^{\left(\alpha, \beta\right)}(x)
|
231 |
+
P_n^{\left(\alpha, \beta\right)}(x)
|
232 |
+
(1-x)^{\alpha} (1+x)^{\beta} \mathrm{d}x
|
233 |
+
= \delta_{m,n}
|
234 |
+
|
235 |
+
Examples
|
236 |
+
========
|
237 |
+
|
238 |
+
>>> from sympy import jacobi_normalized
|
239 |
+
>>> from sympy.abc import n,a,b,x
|
240 |
+
|
241 |
+
>>> jacobi_normalized(n, a, b, x)
|
242 |
+
jacobi(n, a, b, x)/sqrt(2**(a + b + 1)*gamma(a + n + 1)*gamma(b + n + 1)/((a + b + 2*n + 1)*factorial(n)*gamma(a + b + n + 1)))
|
243 |
+
|
244 |
+
Parameters
|
245 |
+
==========
|
246 |
+
|
247 |
+
n : integer degree of polynomial
|
248 |
+
|
249 |
+
a : alpha value
|
250 |
+
|
251 |
+
b : beta value
|
252 |
+
|
253 |
+
x : symbol
|
254 |
+
|
255 |
+
See Also
|
256 |
+
========
|
257 |
+
|
258 |
+
gegenbauer,
|
259 |
+
chebyshevt_root, chebyshevu, chebyshevu_root,
|
260 |
+
legendre, assoc_legendre,
|
261 |
+
hermite, hermite_prob,
|
262 |
+
laguerre, assoc_laguerre,
|
263 |
+
sympy.polys.orthopolys.jacobi_poly,
|
264 |
+
sympy.polys.orthopolys.gegenbauer_poly
|
265 |
+
sympy.polys.orthopolys.chebyshevt_poly
|
266 |
+
sympy.polys.orthopolys.chebyshevu_poly
|
267 |
+
sympy.polys.orthopolys.hermite_poly
|
268 |
+
sympy.polys.orthopolys.legendre_poly
|
269 |
+
sympy.polys.orthopolys.laguerre_poly
|
270 |
+
|
271 |
+
References
|
272 |
+
==========
|
273 |
+
|
274 |
+
.. [1] https://en.wikipedia.org/wiki/Jacobi_polynomials
|
275 |
+
.. [2] https://mathworld.wolfram.com/JacobiPolynomial.html
|
276 |
+
.. [3] https://functions.wolfram.com/Polynomials/JacobiP/
|
277 |
+
|
278 |
+
"""
|
279 |
+
nfactor = (S(2)**(a + b + 1) * (gamma(n + a + 1) * gamma(n + b + 1))
|
280 |
+
/ (2*n + a + b + 1) / (factorial(n) * gamma(n + a + b + 1)))
|
281 |
+
|
282 |
+
return jacobi(n, a, b, x) / sqrt(nfactor)
|
283 |
+
|
284 |
+
|
285 |
+
#----------------------------------------------------------------------------
|
286 |
+
# Gegenbauer polynomials
|
287 |
+
#
|
288 |
+
|
289 |
+
|
290 |
+
class gegenbauer(OrthogonalPolynomial):
|
291 |
+
r"""
|
292 |
+
Gegenbauer polynomial $C_n^{\left(\alpha\right)}(x)$.
|
293 |
+
|
294 |
+
Explanation
|
295 |
+
===========
|
296 |
+
|
297 |
+
``gegenbauer(n, alpha, x)`` gives the $n$th Gegenbauer polynomial
|
298 |
+
in $x$, $C_n^{\left(\alpha\right)}(x)$.
|
299 |
+
|
300 |
+
The Gegenbauer polynomials are orthogonal on $[-1, 1]$ with
|
301 |
+
respect to the weight $\left(1-x^2\right)^{\alpha-\frac{1}{2}}$.
|
302 |
+
|
303 |
+
Examples
|
304 |
+
========
|
305 |
+
|
306 |
+
>>> from sympy import gegenbauer, conjugate, diff
|
307 |
+
>>> from sympy.abc import n,a,x
|
308 |
+
>>> gegenbauer(0, a, x)
|
309 |
+
1
|
310 |
+
>>> gegenbauer(1, a, x)
|
311 |
+
2*a*x
|
312 |
+
>>> gegenbauer(2, a, x)
|
313 |
+
-a + x**2*(2*a**2 + 2*a)
|
314 |
+
>>> gegenbauer(3, a, x)
|
315 |
+
x**3*(4*a**3/3 + 4*a**2 + 8*a/3) + x*(-2*a**2 - 2*a)
|
316 |
+
|
317 |
+
>>> gegenbauer(n, a, x)
|
318 |
+
gegenbauer(n, a, x)
|
319 |
+
>>> gegenbauer(n, a, -x)
|
320 |
+
(-1)**n*gegenbauer(n, a, x)
|
321 |
+
|
322 |
+
>>> gegenbauer(n, a, 0)
|
323 |
+
2**n*sqrt(pi)*gamma(a + n/2)/(gamma(a)*gamma(1/2 - n/2)*gamma(n + 1))
|
324 |
+
>>> gegenbauer(n, a, 1)
|
325 |
+
gamma(2*a + n)/(gamma(2*a)*gamma(n + 1))
|
326 |
+
|
327 |
+
>>> conjugate(gegenbauer(n, a, x))
|
328 |
+
gegenbauer(n, conjugate(a), conjugate(x))
|
329 |
+
|
330 |
+
>>> diff(gegenbauer(n, a, x), x)
|
331 |
+
2*a*gegenbauer(n - 1, a + 1, x)
|
332 |
+
|
333 |
+
See Also
|
334 |
+
========
|
335 |
+
|
336 |
+
jacobi,
|
337 |
+
chebyshevt_root, chebyshevu, chebyshevu_root,
|
338 |
+
legendre, assoc_legendre,
|
339 |
+
hermite, hermite_prob,
|
340 |
+
laguerre, assoc_laguerre,
|
341 |
+
sympy.polys.orthopolys.jacobi_poly
|
342 |
+
sympy.polys.orthopolys.gegenbauer_poly
|
343 |
+
sympy.polys.orthopolys.chebyshevt_poly
|
344 |
+
sympy.polys.orthopolys.chebyshevu_poly
|
345 |
+
sympy.polys.orthopolys.hermite_poly
|
346 |
+
sympy.polys.orthopolys.hermite_prob_poly
|
347 |
+
sympy.polys.orthopolys.legendre_poly
|
348 |
+
sympy.polys.orthopolys.laguerre_poly
|
349 |
+
|
350 |
+
References
|
351 |
+
==========
|
352 |
+
|
353 |
+
.. [1] https://en.wikipedia.org/wiki/Gegenbauer_polynomials
|
354 |
+
.. [2] https://mathworld.wolfram.com/GegenbauerPolynomial.html
|
355 |
+
.. [3] https://functions.wolfram.com/Polynomials/GegenbauerC3/
|
356 |
+
|
357 |
+
"""
|
358 |
+
|
359 |
+
@classmethod
|
360 |
+
def eval(cls, n, a, x):
|
361 |
+
# For negative n the polynomials vanish
|
362 |
+
# See https://functions.wolfram.com/Polynomials/GegenbauerC3/03/01/03/0012/
|
363 |
+
if n.is_negative:
|
364 |
+
return S.Zero
|
365 |
+
|
366 |
+
# Some special values for fixed a
|
367 |
+
if a == S.Half:
|
368 |
+
return legendre(n, x)
|
369 |
+
elif a == S.One:
|
370 |
+
return chebyshevu(n, x)
|
371 |
+
elif a == S.NegativeOne:
|
372 |
+
return S.Zero
|
373 |
+
|
374 |
+
if not n.is_Number:
|
375 |
+
# Handle this before the general sign extraction rule
|
376 |
+
if x == S.NegativeOne:
|
377 |
+
if (re(a) > S.Half) == True:
|
378 |
+
return S.ComplexInfinity
|
379 |
+
else:
|
380 |
+
return (cos(S.Pi*(a+n)) * sec(S.Pi*a) * gamma(2*a+n) /
|
381 |
+
(gamma(2*a) * gamma(n+1)))
|
382 |
+
|
383 |
+
# Symbolic result C^a_n(x)
|
384 |
+
# C^a_n(-x) ---> (-1)**n * C^a_n(x)
|
385 |
+
if x.could_extract_minus_sign():
|
386 |
+
return S.NegativeOne**n * gegenbauer(n, a, -x)
|
387 |
+
# We can evaluate for some special values of x
|
388 |
+
if x.is_zero:
|
389 |
+
return (2**n * sqrt(S.Pi) * gamma(a + S.Half*n) /
|
390 |
+
(gamma((1 - n)/2) * gamma(n + 1) * gamma(a)) )
|
391 |
+
if x == S.One:
|
392 |
+
return gamma(2*a + n) / (gamma(2*a) * gamma(n + 1))
|
393 |
+
elif x is S.Infinity:
|
394 |
+
if n.is_positive:
|
395 |
+
return RisingFactorial(a, n) * S.Infinity
|
396 |
+
else:
|
397 |
+
# n is a given fixed integer, evaluate into polynomial
|
398 |
+
return gegenbauer_poly(n, a, x)
|
399 |
+
|
400 |
+
def fdiff(self, argindex=3):
|
401 |
+
from sympy.concrete.summations import Sum
|
402 |
+
if argindex == 1:
|
403 |
+
# Diff wrt n
|
404 |
+
raise ArgumentIndexError(self, argindex)
|
405 |
+
elif argindex == 2:
|
406 |
+
# Diff wrt a
|
407 |
+
n, a, x = self.args
|
408 |
+
k = Dummy("k")
|
409 |
+
factor1 = 2 * (1 + (-1)**(n - k)) * (k + a) / ((k +
|
410 |
+
n + 2*a) * (n - k))
|
411 |
+
factor2 = 2*(k + 1) / ((k + 2*a) * (2*k + 2*a + 1)) + \
|
412 |
+
2 / (k + n + 2*a)
|
413 |
+
kern = factor1*gegenbauer(k, a, x) + factor2*gegenbauer(n, a, x)
|
414 |
+
return Sum(kern, (k, 0, n - 1))
|
415 |
+
elif argindex == 3:
|
416 |
+
# Diff wrt x
|
417 |
+
n, a, x = self.args
|
418 |
+
return 2*a*gegenbauer(n - 1, a + 1, x)
|
419 |
+
else:
|
420 |
+
raise ArgumentIndexError(self, argindex)
|
421 |
+
|
422 |
+
def _eval_rewrite_as_Sum(self, n, a, x, **kwargs):
|
423 |
+
from sympy.concrete.summations import Sum
|
424 |
+
k = Dummy("k")
|
425 |
+
kern = ((-1)**k * RisingFactorial(a, n - k) * (2*x)**(n - 2*k) /
|
426 |
+
(factorial(k) * factorial(n - 2*k)))
|
427 |
+
return Sum(kern, (k, 0, floor(n/2)))
|
428 |
+
|
429 |
+
def _eval_rewrite_as_polynomial(self, n, a, x, **kwargs):
|
430 |
+
# This function is just kept for backwards compatibility
|
431 |
+
# but should not be used
|
432 |
+
return self._eval_rewrite_as_Sum(n, a, x, **kwargs)
|
433 |
+
|
434 |
+
def _eval_conjugate(self):
|
435 |
+
n, a, x = self.args
|
436 |
+
return self.func(n, a.conjugate(), x.conjugate())
|
437 |
+
|
438 |
+
#----------------------------------------------------------------------------
|
439 |
+
# Chebyshev polynomials of first and second kind
|
440 |
+
#
|
441 |
+
|
442 |
+
|
443 |
+
class chebyshevt(OrthogonalPolynomial):
|
444 |
+
r"""
|
445 |
+
Chebyshev polynomial of the first kind, $T_n(x)$.
|
446 |
+
|
447 |
+
Explanation
|
448 |
+
===========
|
449 |
+
|
450 |
+
``chebyshevt(n, x)`` gives the $n$th Chebyshev polynomial (of the first
|
451 |
+
kind) in $x$, $T_n(x)$.
|
452 |
+
|
453 |
+
The Chebyshev polynomials of the first kind are orthogonal on
|
454 |
+
$[-1, 1]$ with respect to the weight $\frac{1}{\sqrt{1-x^2}}$.
|
455 |
+
|
456 |
+
Examples
|
457 |
+
========
|
458 |
+
|
459 |
+
>>> from sympy import chebyshevt, diff
|
460 |
+
>>> from sympy.abc import n,x
|
461 |
+
>>> chebyshevt(0, x)
|
462 |
+
1
|
463 |
+
>>> chebyshevt(1, x)
|
464 |
+
x
|
465 |
+
>>> chebyshevt(2, x)
|
466 |
+
2*x**2 - 1
|
467 |
+
|
468 |
+
>>> chebyshevt(n, x)
|
469 |
+
chebyshevt(n, x)
|
470 |
+
>>> chebyshevt(n, -x)
|
471 |
+
(-1)**n*chebyshevt(n, x)
|
472 |
+
>>> chebyshevt(-n, x)
|
473 |
+
chebyshevt(n, x)
|
474 |
+
|
475 |
+
>>> chebyshevt(n, 0)
|
476 |
+
cos(pi*n/2)
|
477 |
+
>>> chebyshevt(n, -1)
|
478 |
+
(-1)**n
|
479 |
+
|
480 |
+
>>> diff(chebyshevt(n, x), x)
|
481 |
+
n*chebyshevu(n - 1, x)
|
482 |
+
|
483 |
+
See Also
|
484 |
+
========
|
485 |
+
|
486 |
+
jacobi, gegenbauer,
|
487 |
+
chebyshevt_root, chebyshevu, chebyshevu_root,
|
488 |
+
legendre, assoc_legendre,
|
489 |
+
hermite, hermite_prob,
|
490 |
+
laguerre, assoc_laguerre,
|
491 |
+
sympy.polys.orthopolys.jacobi_poly
|
492 |
+
sympy.polys.orthopolys.gegenbauer_poly
|
493 |
+
sympy.polys.orthopolys.chebyshevt_poly
|
494 |
+
sympy.polys.orthopolys.chebyshevu_poly
|
495 |
+
sympy.polys.orthopolys.hermite_poly
|
496 |
+
sympy.polys.orthopolys.hermite_prob_poly
|
497 |
+
sympy.polys.orthopolys.legendre_poly
|
498 |
+
sympy.polys.orthopolys.laguerre_poly
|
499 |
+
|
500 |
+
References
|
501 |
+
==========
|
502 |
+
|
503 |
+
.. [1] https://en.wikipedia.org/wiki/Chebyshev_polynomial
|
504 |
+
.. [2] https://mathworld.wolfram.com/ChebyshevPolynomialoftheFirstKind.html
|
505 |
+
.. [3] https://mathworld.wolfram.com/ChebyshevPolynomialoftheSecondKind.html
|
506 |
+
.. [4] https://functions.wolfram.com/Polynomials/ChebyshevT/
|
507 |
+
.. [5] https://functions.wolfram.com/Polynomials/ChebyshevU/
|
508 |
+
|
509 |
+
"""
|
510 |
+
|
511 |
+
_ortho_poly = staticmethod(chebyshevt_poly)
|
512 |
+
|
513 |
+
@classmethod
|
514 |
+
def eval(cls, n, x):
|
515 |
+
if not n.is_Number:
|
516 |
+
# Symbolic result T_n(x)
|
517 |
+
# T_n(-x) ---> (-1)**n * T_n(x)
|
518 |
+
if x.could_extract_minus_sign():
|
519 |
+
return S.NegativeOne**n * chebyshevt(n, -x)
|
520 |
+
# T_{-n}(x) ---> T_n(x)
|
521 |
+
if n.could_extract_minus_sign():
|
522 |
+
return chebyshevt(-n, x)
|
523 |
+
# We can evaluate for some special values of x
|
524 |
+
if x.is_zero:
|
525 |
+
return cos(S.Half * S.Pi * n)
|
526 |
+
if x == S.One:
|
527 |
+
return S.One
|
528 |
+
elif x is S.Infinity:
|
529 |
+
return S.Infinity
|
530 |
+
else:
|
531 |
+
# n is a given fixed integer, evaluate into polynomial
|
532 |
+
if n.is_negative:
|
533 |
+
# T_{-n}(x) == T_n(x)
|
534 |
+
return cls._eval_at_order(-n, x)
|
535 |
+
else:
|
536 |
+
return cls._eval_at_order(n, x)
|
537 |
+
|
538 |
+
def fdiff(self, argindex=2):
|
539 |
+
if argindex == 1:
|
540 |
+
# Diff wrt n
|
541 |
+
raise ArgumentIndexError(self, argindex)
|
542 |
+
elif argindex == 2:
|
543 |
+
# Diff wrt x
|
544 |
+
n, x = self.args
|
545 |
+
return n * chebyshevu(n - 1, x)
|
546 |
+
else:
|
547 |
+
raise ArgumentIndexError(self, argindex)
|
548 |
+
|
549 |
+
def _eval_rewrite_as_Sum(self, n, x, **kwargs):
|
550 |
+
from sympy.concrete.summations import Sum
|
551 |
+
k = Dummy("k")
|
552 |
+
kern = binomial(n, 2*k) * (x**2 - 1)**k * x**(n - 2*k)
|
553 |
+
return Sum(kern, (k, 0, floor(n/2)))
|
554 |
+
|
555 |
+
def _eval_rewrite_as_polynomial(self, n, x, **kwargs):
|
556 |
+
# This function is just kept for backwards compatibility
|
557 |
+
# but should not be used
|
558 |
+
return self._eval_rewrite_as_Sum(n, x, **kwargs)
|
559 |
+
|
560 |
+
|
561 |
+
class chebyshevu(OrthogonalPolynomial):
|
562 |
+
r"""
|
563 |
+
Chebyshev polynomial of the second kind, $U_n(x)$.
|
564 |
+
|
565 |
+
Explanation
|
566 |
+
===========
|
567 |
+
|
568 |
+
``chebyshevu(n, x)`` gives the $n$th Chebyshev polynomial of the second
|
569 |
+
kind in x, $U_n(x)$.
|
570 |
+
|
571 |
+
The Chebyshev polynomials of the second kind are orthogonal on
|
572 |
+
$[-1, 1]$ with respect to the weight $\sqrt{1-x^2}$.
|
573 |
+
|
574 |
+
Examples
|
575 |
+
========
|
576 |
+
|
577 |
+
>>> from sympy import chebyshevu, diff
|
578 |
+
>>> from sympy.abc import n,x
|
579 |
+
>>> chebyshevu(0, x)
|
580 |
+
1
|
581 |
+
>>> chebyshevu(1, x)
|
582 |
+
2*x
|
583 |
+
>>> chebyshevu(2, x)
|
584 |
+
4*x**2 - 1
|
585 |
+
|
586 |
+
>>> chebyshevu(n, x)
|
587 |
+
chebyshevu(n, x)
|
588 |
+
>>> chebyshevu(n, -x)
|
589 |
+
(-1)**n*chebyshevu(n, x)
|
590 |
+
>>> chebyshevu(-n, x)
|
591 |
+
-chebyshevu(n - 2, x)
|
592 |
+
|
593 |
+
>>> chebyshevu(n, 0)
|
594 |
+
cos(pi*n/2)
|
595 |
+
>>> chebyshevu(n, 1)
|
596 |
+
n + 1
|
597 |
+
|
598 |
+
>>> diff(chebyshevu(n, x), x)
|
599 |
+
(-x*chebyshevu(n, x) + (n + 1)*chebyshevt(n + 1, x))/(x**2 - 1)
|
600 |
+
|
601 |
+
See Also
|
602 |
+
========
|
603 |
+
|
604 |
+
jacobi, gegenbauer,
|
605 |
+
chebyshevt, chebyshevt_root, chebyshevu_root,
|
606 |
+
legendre, assoc_legendre,
|
607 |
+
hermite, hermite_prob,
|
608 |
+
laguerre, assoc_laguerre,
|
609 |
+
sympy.polys.orthopolys.jacobi_poly
|
610 |
+
sympy.polys.orthopolys.gegenbauer_poly
|
611 |
+
sympy.polys.orthopolys.chebyshevt_poly
|
612 |
+
sympy.polys.orthopolys.chebyshevu_poly
|
613 |
+
sympy.polys.orthopolys.hermite_poly
|
614 |
+
sympy.polys.orthopolys.hermite_prob_poly
|
615 |
+
sympy.polys.orthopolys.legendre_poly
|
616 |
+
sympy.polys.orthopolys.laguerre_poly
|
617 |
+
|
618 |
+
References
|
619 |
+
==========
|
620 |
+
|
621 |
+
.. [1] https://en.wikipedia.org/wiki/Chebyshev_polynomial
|
622 |
+
.. [2] https://mathworld.wolfram.com/ChebyshevPolynomialoftheFirstKind.html
|
623 |
+
.. [3] https://mathworld.wolfram.com/ChebyshevPolynomialoftheSecondKind.html
|
624 |
+
.. [4] https://functions.wolfram.com/Polynomials/ChebyshevT/
|
625 |
+
.. [5] https://functions.wolfram.com/Polynomials/ChebyshevU/
|
626 |
+
|
627 |
+
"""
|
628 |
+
|
629 |
+
_ortho_poly = staticmethod(chebyshevu_poly)
|
630 |
+
|
631 |
+
@classmethod
|
632 |
+
def eval(cls, n, x):
|
633 |
+
if not n.is_Number:
|
634 |
+
# Symbolic result U_n(x)
|
635 |
+
# U_n(-x) ---> (-1)**n * U_n(x)
|
636 |
+
if x.could_extract_minus_sign():
|
637 |
+
return S.NegativeOne**n * chebyshevu(n, -x)
|
638 |
+
# U_{-n}(x) ---> -U_{n-2}(x)
|
639 |
+
if n.could_extract_minus_sign():
|
640 |
+
if n == S.NegativeOne:
|
641 |
+
# n can not be -1 here
|
642 |
+
return S.Zero
|
643 |
+
elif not (-n - 2).could_extract_minus_sign():
|
644 |
+
return -chebyshevu(-n - 2, x)
|
645 |
+
# We can evaluate for some special values of x
|
646 |
+
if x.is_zero:
|
647 |
+
return cos(S.Half * S.Pi * n)
|
648 |
+
if x == S.One:
|
649 |
+
return S.One + n
|
650 |
+
elif x is S.Infinity:
|
651 |
+
return S.Infinity
|
652 |
+
else:
|
653 |
+
# n is a given fixed integer, evaluate into polynomial
|
654 |
+
if n.is_negative:
|
655 |
+
# U_{-n}(x) ---> -U_{n-2}(x)
|
656 |
+
if n == S.NegativeOne:
|
657 |
+
return S.Zero
|
658 |
+
else:
|
659 |
+
return -cls._eval_at_order(-n - 2, x)
|
660 |
+
else:
|
661 |
+
return cls._eval_at_order(n, x)
|
662 |
+
|
663 |
+
def fdiff(self, argindex=2):
|
664 |
+
if argindex == 1:
|
665 |
+
# Diff wrt n
|
666 |
+
raise ArgumentIndexError(self, argindex)
|
667 |
+
elif argindex == 2:
|
668 |
+
# Diff wrt x
|
669 |
+
n, x = self.args
|
670 |
+
return ((n + 1) * chebyshevt(n + 1, x) - x * chebyshevu(n, x)) / (x**2 - 1)
|
671 |
+
else:
|
672 |
+
raise ArgumentIndexError(self, argindex)
|
673 |
+
|
674 |
+
def _eval_rewrite_as_Sum(self, n, x, **kwargs):
|
675 |
+
from sympy.concrete.summations import Sum
|
676 |
+
k = Dummy("k")
|
677 |
+
kern = S.NegativeOne**k * factorial(
|
678 |
+
n - k) * (2*x)**(n - 2*k) / (factorial(k) * factorial(n - 2*k))
|
679 |
+
return Sum(kern, (k, 0, floor(n/2)))
|
680 |
+
|
681 |
+
def _eval_rewrite_as_polynomial(self, n, x, **kwargs):
|
682 |
+
# This function is just kept for backwards compatibility
|
683 |
+
# but should not be used
|
684 |
+
return self._eval_rewrite_as_Sum(n, x, **kwargs)
|
685 |
+
|
686 |
+
|
687 |
+
class chebyshevt_root(Function):
|
688 |
+
r"""
|
689 |
+
``chebyshev_root(n, k)`` returns the $k$th root (indexed from zero) of
|
690 |
+
the $n$th Chebyshev polynomial of the first kind; that is, if
|
691 |
+
$0 \le k < n$, ``chebyshevt(n, chebyshevt_root(n, k)) == 0``.
|
692 |
+
|
693 |
+
Examples
|
694 |
+
========
|
695 |
+
|
696 |
+
>>> from sympy import chebyshevt, chebyshevt_root
|
697 |
+
>>> chebyshevt_root(3, 2)
|
698 |
+
-sqrt(3)/2
|
699 |
+
>>> chebyshevt(3, chebyshevt_root(3, 2))
|
700 |
+
0
|
701 |
+
|
702 |
+
See Also
|
703 |
+
========
|
704 |
+
|
705 |
+
jacobi, gegenbauer,
|
706 |
+
chebyshevt, chebyshevu, chebyshevu_root,
|
707 |
+
legendre, assoc_legendre,
|
708 |
+
hermite, hermite_prob,
|
709 |
+
laguerre, assoc_laguerre,
|
710 |
+
sympy.polys.orthopolys.jacobi_poly
|
711 |
+
sympy.polys.orthopolys.gegenbauer_poly
|
712 |
+
sympy.polys.orthopolys.chebyshevt_poly
|
713 |
+
sympy.polys.orthopolys.chebyshevu_poly
|
714 |
+
sympy.polys.orthopolys.hermite_poly
|
715 |
+
sympy.polys.orthopolys.hermite_prob_poly
|
716 |
+
sympy.polys.orthopolys.legendre_poly
|
717 |
+
sympy.polys.orthopolys.laguerre_poly
|
718 |
+
"""
|
719 |
+
|
720 |
+
@classmethod
|
721 |
+
def eval(cls, n, k):
|
722 |
+
if not ((0 <= k) and (k < n)):
|
723 |
+
raise ValueError("must have 0 <= k < n, "
|
724 |
+
"got k = %s and n = %s" % (k, n))
|
725 |
+
return cos(S.Pi*(2*k + 1)/(2*n))
|
726 |
+
|
727 |
+
|
728 |
+
class chebyshevu_root(Function):
|
729 |
+
r"""
|
730 |
+
``chebyshevu_root(n, k)`` returns the $k$th root (indexed from zero) of the
|
731 |
+
$n$th Chebyshev polynomial of the second kind; that is, if $0 \le k < n$,
|
732 |
+
``chebyshevu(n, chebyshevu_root(n, k)) == 0``.
|
733 |
+
|
734 |
+
Examples
|
735 |
+
========
|
736 |
+
|
737 |
+
>>> from sympy import chebyshevu, chebyshevu_root
|
738 |
+
>>> chebyshevu_root(3, 2)
|
739 |
+
-sqrt(2)/2
|
740 |
+
>>> chebyshevu(3, chebyshevu_root(3, 2))
|
741 |
+
0
|
742 |
+
|
743 |
+
See Also
|
744 |
+
========
|
745 |
+
|
746 |
+
chebyshevt, chebyshevt_root, chebyshevu,
|
747 |
+
legendre, assoc_legendre,
|
748 |
+
hermite, hermite_prob,
|
749 |
+
laguerre, assoc_laguerre,
|
750 |
+
sympy.polys.orthopolys.jacobi_poly
|
751 |
+
sympy.polys.orthopolys.gegenbauer_poly
|
752 |
+
sympy.polys.orthopolys.chebyshevt_poly
|
753 |
+
sympy.polys.orthopolys.chebyshevu_poly
|
754 |
+
sympy.polys.orthopolys.hermite_poly
|
755 |
+
sympy.polys.orthopolys.hermite_prob_poly
|
756 |
+
sympy.polys.orthopolys.legendre_poly
|
757 |
+
sympy.polys.orthopolys.laguerre_poly
|
758 |
+
"""
|
759 |
+
|
760 |
+
|
761 |
+
@classmethod
|
762 |
+
def eval(cls, n, k):
|
763 |
+
if not ((0 <= k) and (k < n)):
|
764 |
+
raise ValueError("must have 0 <= k < n, "
|
765 |
+
"got k = %s and n = %s" % (k, n))
|
766 |
+
return cos(S.Pi*(k + 1)/(n + 1))
|
767 |
+
|
768 |
+
#----------------------------------------------------------------------------
|
769 |
+
# Legendre polynomials and Associated Legendre polynomials
|
770 |
+
#
|
771 |
+
|
772 |
+
|
773 |
+
class legendre(OrthogonalPolynomial):
|
774 |
+
r"""
|
775 |
+
``legendre(n, x)`` gives the $n$th Legendre polynomial of $x$, $P_n(x)$
|
776 |
+
|
777 |
+
Explanation
|
778 |
+
===========
|
779 |
+
|
780 |
+
The Legendre polynomials are orthogonal on $[-1, 1]$ with respect to
|
781 |
+
the constant weight 1. They satisfy $P_n(1) = 1$ for all $n$; further,
|
782 |
+
$P_n$ is odd for odd $n$ and even for even $n$.
|
783 |
+
|
784 |
+
Examples
|
785 |
+
========
|
786 |
+
|
787 |
+
>>> from sympy import legendre, diff
|
788 |
+
>>> from sympy.abc import x, n
|
789 |
+
>>> legendre(0, x)
|
790 |
+
1
|
791 |
+
>>> legendre(1, x)
|
792 |
+
x
|
793 |
+
>>> legendre(2, x)
|
794 |
+
3*x**2/2 - 1/2
|
795 |
+
>>> legendre(n, x)
|
796 |
+
legendre(n, x)
|
797 |
+
>>> diff(legendre(n,x), x)
|
798 |
+
n*(x*legendre(n, x) - legendre(n - 1, x))/(x**2 - 1)
|
799 |
+
|
800 |
+
See Also
|
801 |
+
========
|
802 |
+
|
803 |
+
jacobi, gegenbauer,
|
804 |
+
chebyshevt, chebyshevt_root, chebyshevu, chebyshevu_root,
|
805 |
+
assoc_legendre,
|
806 |
+
hermite, hermite_prob,
|
807 |
+
laguerre, assoc_laguerre,
|
808 |
+
sympy.polys.orthopolys.jacobi_poly
|
809 |
+
sympy.polys.orthopolys.gegenbauer_poly
|
810 |
+
sympy.polys.orthopolys.chebyshevt_poly
|
811 |
+
sympy.polys.orthopolys.chebyshevu_poly
|
812 |
+
sympy.polys.orthopolys.hermite_poly
|
813 |
+
sympy.polys.orthopolys.hermite_prob_poly
|
814 |
+
sympy.polys.orthopolys.legendre_poly
|
815 |
+
sympy.polys.orthopolys.laguerre_poly
|
816 |
+
|
817 |
+
References
|
818 |
+
==========
|
819 |
+
|
820 |
+
.. [1] https://en.wikipedia.org/wiki/Legendre_polynomial
|
821 |
+
.. [2] https://mathworld.wolfram.com/LegendrePolynomial.html
|
822 |
+
.. [3] https://functions.wolfram.com/Polynomials/LegendreP/
|
823 |
+
.. [4] https://functions.wolfram.com/Polynomials/LegendreP2/
|
824 |
+
|
825 |
+
"""
|
826 |
+
|
827 |
+
_ortho_poly = staticmethod(legendre_poly)
|
828 |
+
|
829 |
+
@classmethod
|
830 |
+
def eval(cls, n, x):
|
831 |
+
if not n.is_Number:
|
832 |
+
# Symbolic result L_n(x)
|
833 |
+
# L_n(-x) ---> (-1)**n * L_n(x)
|
834 |
+
if x.could_extract_minus_sign():
|
835 |
+
return S.NegativeOne**n * legendre(n, -x)
|
836 |
+
# L_{-n}(x) ---> L_{n-1}(x)
|
837 |
+
if n.could_extract_minus_sign() and not(-n - 1).could_extract_minus_sign():
|
838 |
+
return legendre(-n - S.One, x)
|
839 |
+
# We can evaluate for some special values of x
|
840 |
+
if x.is_zero:
|
841 |
+
return sqrt(S.Pi)/(gamma(S.Half - n/2)*gamma(S.One + n/2))
|
842 |
+
elif x == S.One:
|
843 |
+
return S.One
|
844 |
+
elif x is S.Infinity:
|
845 |
+
return S.Infinity
|
846 |
+
else:
|
847 |
+
# n is a given fixed integer, evaluate into polynomial;
|
848 |
+
# L_{-n}(x) ---> L_{n-1}(x)
|
849 |
+
if n.is_negative:
|
850 |
+
n = -n - S.One
|
851 |
+
return cls._eval_at_order(n, x)
|
852 |
+
|
853 |
+
def fdiff(self, argindex=2):
|
854 |
+
if argindex == 1:
|
855 |
+
# Diff wrt n
|
856 |
+
raise ArgumentIndexError(self, argindex)
|
857 |
+
elif argindex == 2:
|
858 |
+
# Diff wrt x
|
859 |
+
# Find better formula, this is unsuitable for x = +/-1
|
860 |
+
# https://www.autodiff.org/ad16/Oral/Buecker_Legendre.pdf says
|
861 |
+
# at x = 1:
|
862 |
+
# n*(n + 1)/2 , m = 0
|
863 |
+
# oo , m = 1
|
864 |
+
# -(n-1)*n*(n+1)*(n+2)/4 , m = 2
|
865 |
+
# 0 , m = 3, 4, ..., n
|
866 |
+
#
|
867 |
+
# at x = -1
|
868 |
+
# (-1)**(n+1)*n*(n + 1)/2 , m = 0
|
869 |
+
# (-1)**n*oo , m = 1
|
870 |
+
# (-1)**n*(n-1)*n*(n+1)*(n+2)/4 , m = 2
|
871 |
+
# 0 , m = 3, 4, ..., n
|
872 |
+
n, x = self.args
|
873 |
+
return n/(x**2 - 1)*(x*legendre(n, x) - legendre(n - 1, x))
|
874 |
+
else:
|
875 |
+
raise ArgumentIndexError(self, argindex)
|
876 |
+
|
877 |
+
def _eval_rewrite_as_Sum(self, n, x, **kwargs):
|
878 |
+
from sympy.concrete.summations import Sum
|
879 |
+
k = Dummy("k")
|
880 |
+
kern = S.NegativeOne**k*binomial(n, k)**2*((1 + x)/2)**(n - k)*((1 - x)/2)**k
|
881 |
+
return Sum(kern, (k, 0, n))
|
882 |
+
|
883 |
+
def _eval_rewrite_as_polynomial(self, n, x, **kwargs):
|
884 |
+
# This function is just kept for backwards compatibility
|
885 |
+
# but should not be used
|
886 |
+
return self._eval_rewrite_as_Sum(n, x, **kwargs)
|
887 |
+
|
888 |
+
|
889 |
+
class assoc_legendre(Function):
|
890 |
+
r"""
|
891 |
+
``assoc_legendre(n, m, x)`` gives $P_n^m(x)$, where $n$ and $m$ are
|
892 |
+
the degree and order or an expression which is related to the nth
|
893 |
+
order Legendre polynomial, $P_n(x)$ in the following manner:
|
894 |
+
|
895 |
+
.. math::
|
896 |
+
P_n^m(x) = (-1)^m (1 - x^2)^{\frac{m}{2}}
|
897 |
+
\frac{\mathrm{d}^m P_n(x)}{\mathrm{d} x^m}
|
898 |
+
|
899 |
+
Explanation
|
900 |
+
===========
|
901 |
+
|
902 |
+
Associated Legendre polynomials are orthogonal on $[-1, 1]$ with:
|
903 |
+
|
904 |
+
- weight $= 1$ for the same $m$ and different $n$.
|
905 |
+
- weight $= \frac{1}{1-x^2}$ for the same $n$ and different $m$.
|
906 |
+
|
907 |
+
Examples
|
908 |
+
========
|
909 |
+
|
910 |
+
>>> from sympy import assoc_legendre
|
911 |
+
>>> from sympy.abc import x, m, n
|
912 |
+
>>> assoc_legendre(0,0, x)
|
913 |
+
1
|
914 |
+
>>> assoc_legendre(1,0, x)
|
915 |
+
x
|
916 |
+
>>> assoc_legendre(1,1, x)
|
917 |
+
-sqrt(1 - x**2)
|
918 |
+
>>> assoc_legendre(n,m,x)
|
919 |
+
assoc_legendre(n, m, x)
|
920 |
+
|
921 |
+
See Also
|
922 |
+
========
|
923 |
+
|
924 |
+
jacobi, gegenbauer,
|
925 |
+
chebyshevt, chebyshevt_root, chebyshevu, chebyshevu_root,
|
926 |
+
legendre,
|
927 |
+
hermite, hermite_prob,
|
928 |
+
laguerre, assoc_laguerre,
|
929 |
+
sympy.polys.orthopolys.jacobi_poly
|
930 |
+
sympy.polys.orthopolys.gegenbauer_poly
|
931 |
+
sympy.polys.orthopolys.chebyshevt_poly
|
932 |
+
sympy.polys.orthopolys.chebyshevu_poly
|
933 |
+
sympy.polys.orthopolys.hermite_poly
|
934 |
+
sympy.polys.orthopolys.hermite_prob_poly
|
935 |
+
sympy.polys.orthopolys.legendre_poly
|
936 |
+
sympy.polys.orthopolys.laguerre_poly
|
937 |
+
|
938 |
+
References
|
939 |
+
==========
|
940 |
+
|
941 |
+
.. [1] https://en.wikipedia.org/wiki/Associated_Legendre_polynomials
|
942 |
+
.. [2] https://mathworld.wolfram.com/LegendrePolynomial.html
|
943 |
+
.. [3] https://functions.wolfram.com/Polynomials/LegendreP/
|
944 |
+
.. [4] https://functions.wolfram.com/Polynomials/LegendreP2/
|
945 |
+
|
946 |
+
"""
|
947 |
+
|
948 |
+
@classmethod
|
949 |
+
def _eval_at_order(cls, n, m):
|
950 |
+
P = legendre_poly(n, _x, polys=True).diff((_x, m))
|
951 |
+
return S.NegativeOne**m * (1 - _x**2)**Rational(m, 2) * P.as_expr()
|
952 |
+
|
953 |
+
@classmethod
|
954 |
+
def eval(cls, n, m, x):
|
955 |
+
if m.could_extract_minus_sign():
|
956 |
+
# P^{-m}_n ---> F * P^m_n
|
957 |
+
return S.NegativeOne**(-m) * (factorial(m + n)/factorial(n - m)) * assoc_legendre(n, -m, x)
|
958 |
+
if m == 0:
|
959 |
+
# P^0_n ---> L_n
|
960 |
+
return legendre(n, x)
|
961 |
+
if x == 0:
|
962 |
+
return 2**m*sqrt(S.Pi) / (gamma((1 - m - n)/2)*gamma(1 - (m - n)/2))
|
963 |
+
if n.is_Number and m.is_Number and n.is_integer and m.is_integer:
|
964 |
+
if n.is_negative:
|
965 |
+
raise ValueError("%s : 1st index must be nonnegative integer (got %r)" % (cls, n))
|
966 |
+
if abs(m) > n:
|
967 |
+
raise ValueError("%s : abs('2nd index') must be <= '1st index' (got %r, %r)" % (cls, n, m))
|
968 |
+
return cls._eval_at_order(int(n), abs(int(m))).subs(_x, x)
|
969 |
+
|
970 |
+
def fdiff(self, argindex=3):
|
971 |
+
if argindex == 1:
|
972 |
+
# Diff wrt n
|
973 |
+
raise ArgumentIndexError(self, argindex)
|
974 |
+
elif argindex == 2:
|
975 |
+
# Diff wrt m
|
976 |
+
raise ArgumentIndexError(self, argindex)
|
977 |
+
elif argindex == 3:
|
978 |
+
# Diff wrt x
|
979 |
+
# Find better formula, this is unsuitable for x = 1
|
980 |
+
n, m, x = self.args
|
981 |
+
return 1/(x**2 - 1)*(x*n*assoc_legendre(n, m, x) - (m + n)*assoc_legendre(n - 1, m, x))
|
982 |
+
else:
|
983 |
+
raise ArgumentIndexError(self, argindex)
|
984 |
+
|
985 |
+
def _eval_rewrite_as_Sum(self, n, m, x, **kwargs):
|
986 |
+
from sympy.concrete.summations import Sum
|
987 |
+
k = Dummy("k")
|
988 |
+
kern = factorial(2*n - 2*k)/(2**n*factorial(n - k)*factorial(
|
989 |
+
k)*factorial(n - 2*k - m))*S.NegativeOne**k*x**(n - m - 2*k)
|
990 |
+
return (1 - x**2)**(m/2) * Sum(kern, (k, 0, floor((n - m)*S.Half)))
|
991 |
+
|
992 |
+
def _eval_rewrite_as_polynomial(self, n, m, x, **kwargs):
|
993 |
+
# This function is just kept for backwards compatibility
|
994 |
+
# but should not be used
|
995 |
+
return self._eval_rewrite_as_Sum(n, m, x, **kwargs)
|
996 |
+
|
997 |
+
def _eval_conjugate(self):
|
998 |
+
n, m, x = self.args
|
999 |
+
return self.func(n, m.conjugate(), x.conjugate())
|
1000 |
+
|
1001 |
+
#----------------------------------------------------------------------------
|
1002 |
+
# Hermite polynomials
|
1003 |
+
#
|
1004 |
+
|
1005 |
+
|
1006 |
+
class hermite(OrthogonalPolynomial):
|
1007 |
+
r"""
|
1008 |
+
``hermite(n, x)`` gives the $n$th Hermite polynomial in $x$, $H_n(x)$.
|
1009 |
+
|
1010 |
+
Explanation
|
1011 |
+
===========
|
1012 |
+
|
1013 |
+
The Hermite polynomials are orthogonal on $(-\infty, \infty)$
|
1014 |
+
with respect to the weight $\exp\left(-x^2\right)$.
|
1015 |
+
|
1016 |
+
Examples
|
1017 |
+
========
|
1018 |
+
|
1019 |
+
>>> from sympy import hermite, diff
|
1020 |
+
>>> from sympy.abc import x, n
|
1021 |
+
>>> hermite(0, x)
|
1022 |
+
1
|
1023 |
+
>>> hermite(1, x)
|
1024 |
+
2*x
|
1025 |
+
>>> hermite(2, x)
|
1026 |
+
4*x**2 - 2
|
1027 |
+
>>> hermite(n, x)
|
1028 |
+
hermite(n, x)
|
1029 |
+
>>> diff(hermite(n,x), x)
|
1030 |
+
2*n*hermite(n - 1, x)
|
1031 |
+
>>> hermite(n, -x)
|
1032 |
+
(-1)**n*hermite(n, x)
|
1033 |
+
|
1034 |
+
See Also
|
1035 |
+
========
|
1036 |
+
|
1037 |
+
jacobi, gegenbauer,
|
1038 |
+
chebyshevt, chebyshevt_root, chebyshevu, chebyshevu_root,
|
1039 |
+
legendre, assoc_legendre,
|
1040 |
+
hermite_prob,
|
1041 |
+
laguerre, assoc_laguerre,
|
1042 |
+
sympy.polys.orthopolys.jacobi_poly
|
1043 |
+
sympy.polys.orthopolys.gegenbauer_poly
|
1044 |
+
sympy.polys.orthopolys.chebyshevt_poly
|
1045 |
+
sympy.polys.orthopolys.chebyshevu_poly
|
1046 |
+
sympy.polys.orthopolys.hermite_poly
|
1047 |
+
sympy.polys.orthopolys.hermite_prob_poly
|
1048 |
+
sympy.polys.orthopolys.legendre_poly
|
1049 |
+
sympy.polys.orthopolys.laguerre_poly
|
1050 |
+
|
1051 |
+
References
|
1052 |
+
==========
|
1053 |
+
|
1054 |
+
.. [1] https://en.wikipedia.org/wiki/Hermite_polynomial
|
1055 |
+
.. [2] https://mathworld.wolfram.com/HermitePolynomial.html
|
1056 |
+
.. [3] https://functions.wolfram.com/Polynomials/HermiteH/
|
1057 |
+
|
1058 |
+
"""
|
1059 |
+
|
1060 |
+
_ortho_poly = staticmethod(hermite_poly)
|
1061 |
+
|
1062 |
+
@classmethod
|
1063 |
+
def eval(cls, n, x):
|
1064 |
+
if not n.is_Number:
|
1065 |
+
# Symbolic result H_n(x)
|
1066 |
+
# H_n(-x) ---> (-1)**n * H_n(x)
|
1067 |
+
if x.could_extract_minus_sign():
|
1068 |
+
return S.NegativeOne**n * hermite(n, -x)
|
1069 |
+
# We can evaluate for some special values of x
|
1070 |
+
if x.is_zero:
|
1071 |
+
return 2**n * sqrt(S.Pi) / gamma((S.One - n)/2)
|
1072 |
+
elif x is S.Infinity:
|
1073 |
+
return S.Infinity
|
1074 |
+
else:
|
1075 |
+
# n is a given fixed integer, evaluate into polynomial
|
1076 |
+
if n.is_negative:
|
1077 |
+
raise ValueError(
|
1078 |
+
"The index n must be nonnegative integer (got %r)" % n)
|
1079 |
+
else:
|
1080 |
+
return cls._eval_at_order(n, x)
|
1081 |
+
|
1082 |
+
def fdiff(self, argindex=2):
|
1083 |
+
if argindex == 1:
|
1084 |
+
# Diff wrt n
|
1085 |
+
raise ArgumentIndexError(self, argindex)
|
1086 |
+
elif argindex == 2:
|
1087 |
+
# Diff wrt x
|
1088 |
+
n, x = self.args
|
1089 |
+
return 2*n*hermite(n - 1, x)
|
1090 |
+
else:
|
1091 |
+
raise ArgumentIndexError(self, argindex)
|
1092 |
+
|
1093 |
+
def _eval_rewrite_as_Sum(self, n, x, **kwargs):
|
1094 |
+
from sympy.concrete.summations import Sum
|
1095 |
+
k = Dummy("k")
|
1096 |
+
kern = S.NegativeOne**k / (factorial(k)*factorial(n - 2*k)) * (2*x)**(n - 2*k)
|
1097 |
+
return factorial(n)*Sum(kern, (k, 0, floor(n/2)))
|
1098 |
+
|
1099 |
+
def _eval_rewrite_as_polynomial(self, n, x, **kwargs):
|
1100 |
+
# This function is just kept for backwards compatibility
|
1101 |
+
# but should not be used
|
1102 |
+
return self._eval_rewrite_as_Sum(n, x, **kwargs)
|
1103 |
+
|
1104 |
+
def _eval_rewrite_as_hermite_prob(self, n, x, **kwargs):
|
1105 |
+
return sqrt(2)**n * hermite_prob(n, x*sqrt(2))
|
1106 |
+
|
1107 |
+
|
1108 |
+
class hermite_prob(OrthogonalPolynomial):
|
1109 |
+
r"""
|
1110 |
+
``hermite_prob(n, x)`` gives the $n$th probabilist's Hermite polynomial
|
1111 |
+
in $x$, $He_n(x)$.
|
1112 |
+
|
1113 |
+
Explanation
|
1114 |
+
===========
|
1115 |
+
|
1116 |
+
The probabilist's Hermite polynomials are orthogonal on $(-\infty, \infty)$
|
1117 |
+
with respect to the weight $\exp\left(-\frac{x^2}{2}\right)$. They are monic
|
1118 |
+
polynomials, related to the plain Hermite polynomials (:py:class:`~.hermite`) by
|
1119 |
+
|
1120 |
+
.. math :: He_n(x) = 2^{-n/2} H_n(x/\sqrt{2})
|
1121 |
+
|
1122 |
+
Examples
|
1123 |
+
========
|
1124 |
+
|
1125 |
+
>>> from sympy import hermite_prob, diff, I
|
1126 |
+
>>> from sympy.abc import x, n
|
1127 |
+
>>> hermite_prob(1, x)
|
1128 |
+
x
|
1129 |
+
>>> hermite_prob(5, x)
|
1130 |
+
x**5 - 10*x**3 + 15*x
|
1131 |
+
>>> diff(hermite_prob(n,x), x)
|
1132 |
+
n*hermite_prob(n - 1, x)
|
1133 |
+
>>> hermite_prob(n, -x)
|
1134 |
+
(-1)**n*hermite_prob(n, x)
|
1135 |
+
|
1136 |
+
The sum of absolute values of coefficients of $He_n(x)$ is the number of
|
1137 |
+
matchings in the complete graph $K_n$ or telephone number, A000085 in the OEIS:
|
1138 |
+
|
1139 |
+
>>> [hermite_prob(n,I) / I**n for n in range(11)]
|
1140 |
+
[1, 1, 2, 4, 10, 26, 76, 232, 764, 2620, 9496]
|
1141 |
+
|
1142 |
+
See Also
|
1143 |
+
========
|
1144 |
+
|
1145 |
+
jacobi, gegenbauer,
|
1146 |
+
chebyshevt, chebyshevt_root, chebyshevu, chebyshevu_root,
|
1147 |
+
legendre, assoc_legendre,
|
1148 |
+
hermite,
|
1149 |
+
laguerre, assoc_laguerre,
|
1150 |
+
sympy.polys.orthopolys.jacobi_poly
|
1151 |
+
sympy.polys.orthopolys.gegenbauer_poly
|
1152 |
+
sympy.polys.orthopolys.chebyshevt_poly
|
1153 |
+
sympy.polys.orthopolys.chebyshevu_poly
|
1154 |
+
sympy.polys.orthopolys.hermite_poly
|
1155 |
+
sympy.polys.orthopolys.hermite_prob_poly
|
1156 |
+
sympy.polys.orthopolys.legendre_poly
|
1157 |
+
sympy.polys.orthopolys.laguerre_poly
|
1158 |
+
|
1159 |
+
References
|
1160 |
+
==========
|
1161 |
+
|
1162 |
+
.. [1] https://en.wikipedia.org/wiki/Hermite_polynomial
|
1163 |
+
.. [2] https://mathworld.wolfram.com/HermitePolynomial.html
|
1164 |
+
"""
|
1165 |
+
|
1166 |
+
_ortho_poly = staticmethod(hermite_prob_poly)
|
1167 |
+
|
1168 |
+
@classmethod
|
1169 |
+
def eval(cls, n, x):
|
1170 |
+
if not n.is_Number:
|
1171 |
+
if x.could_extract_minus_sign():
|
1172 |
+
return S.NegativeOne**n * hermite_prob(n, -x)
|
1173 |
+
if x.is_zero:
|
1174 |
+
return sqrt(S.Pi) / gamma((S.One-n) / 2)
|
1175 |
+
elif x is S.Infinity:
|
1176 |
+
return S.Infinity
|
1177 |
+
else:
|
1178 |
+
if n.is_negative:
|
1179 |
+
ValueError("n must be a nonnegative integer, not %r" % n)
|
1180 |
+
else:
|
1181 |
+
return cls._eval_at_order(n, x)
|
1182 |
+
|
1183 |
+
def fdiff(self, argindex=2):
|
1184 |
+
if argindex == 2:
|
1185 |
+
n, x = self.args
|
1186 |
+
return n*hermite_prob(n-1, x)
|
1187 |
+
else:
|
1188 |
+
raise ArgumentIndexError(self, argindex)
|
1189 |
+
|
1190 |
+
def _eval_rewrite_as_Sum(self, n, x, **kwargs):
|
1191 |
+
from sympy.concrete.summations import Sum
|
1192 |
+
k = Dummy("k")
|
1193 |
+
kern = (-S.Half)**k * x**(n-2*k) / (factorial(k) * factorial(n-2*k))
|
1194 |
+
return factorial(n)*Sum(kern, (k, 0, floor(n/2)))
|
1195 |
+
|
1196 |
+
def _eval_rewrite_as_polynomial(self, n, x, **kwargs):
|
1197 |
+
# This function is just kept for backwards compatibility
|
1198 |
+
# but should not be used
|
1199 |
+
return self._eval_rewrite_as_Sum(n, x, **kwargs)
|
1200 |
+
|
1201 |
+
def _eval_rewrite_as_hermite(self, n, x, **kwargs):
|
1202 |
+
return sqrt(2)**(-n) * hermite(n, x/sqrt(2))
|
1203 |
+
|
1204 |
+
|
1205 |
+
#----------------------------------------------------------------------------
|
1206 |
+
# Laguerre polynomials
|
1207 |
+
#
|
1208 |
+
|
1209 |
+
|
1210 |
+
class laguerre(OrthogonalPolynomial):
|
1211 |
+
r"""
|
1212 |
+
Returns the $n$th Laguerre polynomial in $x$, $L_n(x)$.
|
1213 |
+
|
1214 |
+
Examples
|
1215 |
+
========
|
1216 |
+
|
1217 |
+
>>> from sympy import laguerre, diff
|
1218 |
+
>>> from sympy.abc import x, n
|
1219 |
+
>>> laguerre(0, x)
|
1220 |
+
1
|
1221 |
+
>>> laguerre(1, x)
|
1222 |
+
1 - x
|
1223 |
+
>>> laguerre(2, x)
|
1224 |
+
x**2/2 - 2*x + 1
|
1225 |
+
>>> laguerre(3, x)
|
1226 |
+
-x**3/6 + 3*x**2/2 - 3*x + 1
|
1227 |
+
|
1228 |
+
>>> laguerre(n, x)
|
1229 |
+
laguerre(n, x)
|
1230 |
+
|
1231 |
+
>>> diff(laguerre(n, x), x)
|
1232 |
+
-assoc_laguerre(n - 1, 1, x)
|
1233 |
+
|
1234 |
+
Parameters
|
1235 |
+
==========
|
1236 |
+
|
1237 |
+
n : int
|
1238 |
+
Degree of Laguerre polynomial. Must be `n \ge 0`.
|
1239 |
+
|
1240 |
+
See Also
|
1241 |
+
========
|
1242 |
+
|
1243 |
+
jacobi, gegenbauer,
|
1244 |
+
chebyshevt, chebyshevt_root, chebyshevu, chebyshevu_root,
|
1245 |
+
legendre, assoc_legendre,
|
1246 |
+
hermite, hermite_prob,
|
1247 |
+
assoc_laguerre,
|
1248 |
+
sympy.polys.orthopolys.jacobi_poly
|
1249 |
+
sympy.polys.orthopolys.gegenbauer_poly
|
1250 |
+
sympy.polys.orthopolys.chebyshevt_poly
|
1251 |
+
sympy.polys.orthopolys.chebyshevu_poly
|
1252 |
+
sympy.polys.orthopolys.hermite_poly
|
1253 |
+
sympy.polys.orthopolys.hermite_prob_poly
|
1254 |
+
sympy.polys.orthopolys.legendre_poly
|
1255 |
+
sympy.polys.orthopolys.laguerre_poly
|
1256 |
+
|
1257 |
+
References
|
1258 |
+
==========
|
1259 |
+
|
1260 |
+
.. [1] https://en.wikipedia.org/wiki/Laguerre_polynomial
|
1261 |
+
.. [2] https://mathworld.wolfram.com/LaguerrePolynomial.html
|
1262 |
+
.. [3] https://functions.wolfram.com/Polynomials/LaguerreL/
|
1263 |
+
.. [4] https://functions.wolfram.com/Polynomials/LaguerreL3/
|
1264 |
+
|
1265 |
+
"""
|
1266 |
+
|
1267 |
+
_ortho_poly = staticmethod(laguerre_poly)
|
1268 |
+
|
1269 |
+
@classmethod
|
1270 |
+
def eval(cls, n, x):
|
1271 |
+
if n.is_integer is False:
|
1272 |
+
raise ValueError("Error: n should be an integer.")
|
1273 |
+
if not n.is_Number:
|
1274 |
+
# Symbolic result L_n(x)
|
1275 |
+
# L_{n}(-x) ---> exp(-x) * L_{-n-1}(x)
|
1276 |
+
# L_{-n}(x) ---> exp(x) * L_{n-1}(-x)
|
1277 |
+
if n.could_extract_minus_sign() and not(-n - 1).could_extract_minus_sign():
|
1278 |
+
return exp(x)*laguerre(-n - 1, -x)
|
1279 |
+
# We can evaluate for some special values of x
|
1280 |
+
if x.is_zero:
|
1281 |
+
return S.One
|
1282 |
+
elif x is S.NegativeInfinity:
|
1283 |
+
return S.Infinity
|
1284 |
+
elif x is S.Infinity:
|
1285 |
+
return S.NegativeOne**n * S.Infinity
|
1286 |
+
else:
|
1287 |
+
if n.is_negative:
|
1288 |
+
return exp(x)*laguerre(-n - 1, -x)
|
1289 |
+
else:
|
1290 |
+
return cls._eval_at_order(n, x)
|
1291 |
+
|
1292 |
+
def fdiff(self, argindex=2):
|
1293 |
+
if argindex == 1:
|
1294 |
+
# Diff wrt n
|
1295 |
+
raise ArgumentIndexError(self, argindex)
|
1296 |
+
elif argindex == 2:
|
1297 |
+
# Diff wrt x
|
1298 |
+
n, x = self.args
|
1299 |
+
return -assoc_laguerre(n - 1, 1, x)
|
1300 |
+
else:
|
1301 |
+
raise ArgumentIndexError(self, argindex)
|
1302 |
+
|
1303 |
+
def _eval_rewrite_as_Sum(self, n, x, **kwargs):
|
1304 |
+
from sympy.concrete.summations import Sum
|
1305 |
+
# Make sure n \in N_0
|
1306 |
+
if n.is_negative:
|
1307 |
+
return exp(x) * self._eval_rewrite_as_Sum(-n - 1, -x, **kwargs)
|
1308 |
+
if n.is_integer is False:
|
1309 |
+
raise ValueError("Error: n should be an integer.")
|
1310 |
+
k = Dummy("k")
|
1311 |
+
kern = RisingFactorial(-n, k) / factorial(k)**2 * x**k
|
1312 |
+
return Sum(kern, (k, 0, n))
|
1313 |
+
|
1314 |
+
def _eval_rewrite_as_polynomial(self, n, x, **kwargs):
|
1315 |
+
# This function is just kept for backwards compatibility
|
1316 |
+
# but should not be used
|
1317 |
+
return self._eval_rewrite_as_Sum(n, x, **kwargs)
|
1318 |
+
|
1319 |
+
|
1320 |
+
class assoc_laguerre(OrthogonalPolynomial):
|
1321 |
+
r"""
|
1322 |
+
Returns the $n$th generalized Laguerre polynomial in $x$, $L_n(x)$.
|
1323 |
+
|
1324 |
+
Examples
|
1325 |
+
========
|
1326 |
+
|
1327 |
+
>>> from sympy import assoc_laguerre, diff
|
1328 |
+
>>> from sympy.abc import x, n, a
|
1329 |
+
>>> assoc_laguerre(0, a, x)
|
1330 |
+
1
|
1331 |
+
>>> assoc_laguerre(1, a, x)
|
1332 |
+
a - x + 1
|
1333 |
+
>>> assoc_laguerre(2, a, x)
|
1334 |
+
a**2/2 + 3*a/2 + x**2/2 + x*(-a - 2) + 1
|
1335 |
+
>>> assoc_laguerre(3, a, x)
|
1336 |
+
a**3/6 + a**2 + 11*a/6 - x**3/6 + x**2*(a/2 + 3/2) +
|
1337 |
+
x*(-a**2/2 - 5*a/2 - 3) + 1
|
1338 |
+
|
1339 |
+
>>> assoc_laguerre(n, a, 0)
|
1340 |
+
binomial(a + n, a)
|
1341 |
+
|
1342 |
+
>>> assoc_laguerre(n, a, x)
|
1343 |
+
assoc_laguerre(n, a, x)
|
1344 |
+
|
1345 |
+
>>> assoc_laguerre(n, 0, x)
|
1346 |
+
laguerre(n, x)
|
1347 |
+
|
1348 |
+
>>> diff(assoc_laguerre(n, a, x), x)
|
1349 |
+
-assoc_laguerre(n - 1, a + 1, x)
|
1350 |
+
|
1351 |
+
>>> diff(assoc_laguerre(n, a, x), a)
|
1352 |
+
Sum(assoc_laguerre(_k, a, x)/(-a + n), (_k, 0, n - 1))
|
1353 |
+
|
1354 |
+
Parameters
|
1355 |
+
==========
|
1356 |
+
|
1357 |
+
n : int
|
1358 |
+
Degree of Laguerre polynomial. Must be `n \ge 0`.
|
1359 |
+
|
1360 |
+
alpha : Expr
|
1361 |
+
Arbitrary expression. For ``alpha=0`` regular Laguerre
|
1362 |
+
polynomials will be generated.
|
1363 |
+
|
1364 |
+
See Also
|
1365 |
+
========
|
1366 |
+
|
1367 |
+
jacobi, gegenbauer,
|
1368 |
+
chebyshevt, chebyshevt_root, chebyshevu, chebyshevu_root,
|
1369 |
+
legendre, assoc_legendre,
|
1370 |
+
hermite, hermite_prob,
|
1371 |
+
laguerre,
|
1372 |
+
sympy.polys.orthopolys.jacobi_poly
|
1373 |
+
sympy.polys.orthopolys.gegenbauer_poly
|
1374 |
+
sympy.polys.orthopolys.chebyshevt_poly
|
1375 |
+
sympy.polys.orthopolys.chebyshevu_poly
|
1376 |
+
sympy.polys.orthopolys.hermite_poly
|
1377 |
+
sympy.polys.orthopolys.hermite_prob_poly
|
1378 |
+
sympy.polys.orthopolys.legendre_poly
|
1379 |
+
sympy.polys.orthopolys.laguerre_poly
|
1380 |
+
|
1381 |
+
References
|
1382 |
+
==========
|
1383 |
+
|
1384 |
+
.. [1] https://en.wikipedia.org/wiki/Laguerre_polynomial#Generalized_Laguerre_polynomials
|
1385 |
+
.. [2] https://mathworld.wolfram.com/AssociatedLaguerrePolynomial.html
|
1386 |
+
.. [3] https://functions.wolfram.com/Polynomials/LaguerreL/
|
1387 |
+
.. [4] https://functions.wolfram.com/Polynomials/LaguerreL3/
|
1388 |
+
|
1389 |
+
"""
|
1390 |
+
|
1391 |
+
@classmethod
|
1392 |
+
def eval(cls, n, alpha, x):
|
1393 |
+
# L_{n}^{0}(x) ---> L_{n}(x)
|
1394 |
+
if alpha.is_zero:
|
1395 |
+
return laguerre(n, x)
|
1396 |
+
|
1397 |
+
if not n.is_Number:
|
1398 |
+
# We can evaluate for some special values of x
|
1399 |
+
if x.is_zero:
|
1400 |
+
return binomial(n + alpha, alpha)
|
1401 |
+
elif x is S.Infinity and n > 0:
|
1402 |
+
return S.NegativeOne**n * S.Infinity
|
1403 |
+
elif x is S.NegativeInfinity and n > 0:
|
1404 |
+
return S.Infinity
|
1405 |
+
else:
|
1406 |
+
# n is a given fixed integer, evaluate into polynomial
|
1407 |
+
if n.is_negative:
|
1408 |
+
raise ValueError(
|
1409 |
+
"The index n must be nonnegative integer (got %r)" % n)
|
1410 |
+
else:
|
1411 |
+
return laguerre_poly(n, x, alpha)
|
1412 |
+
|
1413 |
+
def fdiff(self, argindex=3):
|
1414 |
+
from sympy.concrete.summations import Sum
|
1415 |
+
if argindex == 1:
|
1416 |
+
# Diff wrt n
|
1417 |
+
raise ArgumentIndexError(self, argindex)
|
1418 |
+
elif argindex == 2:
|
1419 |
+
# Diff wrt alpha
|
1420 |
+
n, alpha, x = self.args
|
1421 |
+
k = Dummy("k")
|
1422 |
+
return Sum(assoc_laguerre(k, alpha, x) / (n - alpha), (k, 0, n - 1))
|
1423 |
+
elif argindex == 3:
|
1424 |
+
# Diff wrt x
|
1425 |
+
n, alpha, x = self.args
|
1426 |
+
return -assoc_laguerre(n - 1, alpha + 1, x)
|
1427 |
+
else:
|
1428 |
+
raise ArgumentIndexError(self, argindex)
|
1429 |
+
|
1430 |
+
def _eval_rewrite_as_Sum(self, n, alpha, x, **kwargs):
|
1431 |
+
from sympy.concrete.summations import Sum
|
1432 |
+
# Make sure n \in N_0
|
1433 |
+
if n.is_negative or n.is_integer is False:
|
1434 |
+
raise ValueError("Error: n should be a non-negative integer.")
|
1435 |
+
k = Dummy("k")
|
1436 |
+
kern = RisingFactorial(
|
1437 |
+
-n, k) / (gamma(k + alpha + 1) * factorial(k)) * x**k
|
1438 |
+
return gamma(n + alpha + 1) / factorial(n) * Sum(kern, (k, 0, n))
|
1439 |
+
|
1440 |
+
def _eval_rewrite_as_polynomial(self, n, alpha, x, **kwargs):
|
1441 |
+
# This function is just kept for backwards compatibility
|
1442 |
+
# but should not be used
|
1443 |
+
return self._eval_rewrite_as_Sum(n, alpha, x, **kwargs)
|
1444 |
+
|
1445 |
+
def _eval_conjugate(self):
|
1446 |
+
n, alpha, x = self.args
|
1447 |
+
return self.func(n, alpha.conjugate(), x.conjugate())
|
venv/lib/python3.10/site-packages/sympy/functions/special/singularity_functions.py
ADDED
@@ -0,0 +1,228 @@
|
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|
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|
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|
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|
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|
|
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|
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|
|
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|
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|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
1 |
+
from sympy.core import S, oo, diff
|
2 |
+
from sympy.core.function import Function, ArgumentIndexError
|
3 |
+
from sympy.core.logic import fuzzy_not
|
4 |
+
from sympy.core.relational import Eq
|
5 |
+
from sympy.functions.elementary.complexes import im
|
6 |
+
from sympy.functions.elementary.piecewise import Piecewise
|
7 |
+
from sympy.functions.special.delta_functions import Heaviside
|
8 |
+
|
9 |
+
###############################################################################
|
10 |
+
############################# SINGULARITY FUNCTION ############################
|
11 |
+
###############################################################################
|
12 |
+
|
13 |
+
|
14 |
+
class SingularityFunction(Function):
|
15 |
+
r"""
|
16 |
+
Singularity functions are a class of discontinuous functions.
|
17 |
+
|
18 |
+
Explanation
|
19 |
+
===========
|
20 |
+
|
21 |
+
Singularity functions take a variable, an offset, and an exponent as
|
22 |
+
arguments. These functions are represented using Macaulay brackets as:
|
23 |
+
|
24 |
+
SingularityFunction(x, a, n) := <x - a>^n
|
25 |
+
|
26 |
+
The singularity function will automatically evaluate to
|
27 |
+
``Derivative(DiracDelta(x - a), x, -n - 1)`` if ``n < 0``
|
28 |
+
and ``(x - a)**n*Heaviside(x - a)`` if ``n >= 0``.
|
29 |
+
|
30 |
+
Examples
|
31 |
+
========
|
32 |
+
|
33 |
+
>>> from sympy import SingularityFunction, diff, Piecewise, DiracDelta, Heaviside, Symbol
|
34 |
+
>>> from sympy.abc import x, a, n
|
35 |
+
>>> SingularityFunction(x, a, n)
|
36 |
+
SingularityFunction(x, a, n)
|
37 |
+
>>> y = Symbol('y', positive=True)
|
38 |
+
>>> n = Symbol('n', nonnegative=True)
|
39 |
+
>>> SingularityFunction(y, -10, n)
|
40 |
+
(y + 10)**n
|
41 |
+
>>> y = Symbol('y', negative=True)
|
42 |
+
>>> SingularityFunction(y, 10, n)
|
43 |
+
0
|
44 |
+
>>> SingularityFunction(x, 4, -1).subs(x, 4)
|
45 |
+
oo
|
46 |
+
>>> SingularityFunction(x, 10, -2).subs(x, 10)
|
47 |
+
oo
|
48 |
+
>>> SingularityFunction(4, 1, 5)
|
49 |
+
243
|
50 |
+
>>> diff(SingularityFunction(x, 1, 5) + SingularityFunction(x, 1, 4), x)
|
51 |
+
4*SingularityFunction(x, 1, 3) + 5*SingularityFunction(x, 1, 4)
|
52 |
+
>>> diff(SingularityFunction(x, 4, 0), x, 2)
|
53 |
+
SingularityFunction(x, 4, -2)
|
54 |
+
>>> SingularityFunction(x, 4, 5).rewrite(Piecewise)
|
55 |
+
Piecewise(((x - 4)**5, x > 4), (0, True))
|
56 |
+
>>> expr = SingularityFunction(x, a, n)
|
57 |
+
>>> y = Symbol('y', positive=True)
|
58 |
+
>>> n = Symbol('n', nonnegative=True)
|
59 |
+
>>> expr.subs({x: y, a: -10, n: n})
|
60 |
+
(y + 10)**n
|
61 |
+
|
62 |
+
The methods ``rewrite(DiracDelta)``, ``rewrite(Heaviside)``, and
|
63 |
+
``rewrite('HeavisideDiracDelta')`` returns the same output. One can use any
|
64 |
+
of these methods according to their choice.
|
65 |
+
|
66 |
+
>>> expr = SingularityFunction(x, 4, 5) + SingularityFunction(x, -3, -1) - SingularityFunction(x, 0, -2)
|
67 |
+
>>> expr.rewrite(Heaviside)
|
68 |
+
(x - 4)**5*Heaviside(x - 4) + DiracDelta(x + 3) - DiracDelta(x, 1)
|
69 |
+
>>> expr.rewrite(DiracDelta)
|
70 |
+
(x - 4)**5*Heaviside(x - 4) + DiracDelta(x + 3) - DiracDelta(x, 1)
|
71 |
+
>>> expr.rewrite('HeavisideDiracDelta')
|
72 |
+
(x - 4)**5*Heaviside(x - 4) + DiracDelta(x + 3) - DiracDelta(x, 1)
|
73 |
+
|
74 |
+
See Also
|
75 |
+
========
|
76 |
+
|
77 |
+
DiracDelta, Heaviside
|
78 |
+
|
79 |
+
References
|
80 |
+
==========
|
81 |
+
|
82 |
+
.. [1] https://en.wikipedia.org/wiki/Singularity_function
|
83 |
+
|
84 |
+
"""
|
85 |
+
|
86 |
+
is_real = True
|
87 |
+
|
88 |
+
def fdiff(self, argindex=1):
|
89 |
+
"""
|
90 |
+
Returns the first derivative of a DiracDelta Function.
|
91 |
+
|
92 |
+
Explanation
|
93 |
+
===========
|
94 |
+
|
95 |
+
The difference between ``diff()`` and ``fdiff()`` is: ``diff()`` is the
|
96 |
+
user-level function and ``fdiff()`` is an object method. ``fdiff()`` is
|
97 |
+
a convenience method available in the ``Function`` class. It returns
|
98 |
+
the derivative of the function without considering the chain rule.
|
99 |
+
``diff(function, x)`` calls ``Function._eval_derivative`` which in turn
|
100 |
+
calls ``fdiff()`` internally to compute the derivative of the function.
|
101 |
+
|
102 |
+
"""
|
103 |
+
|
104 |
+
if argindex == 1:
|
105 |
+
x, a, n = self.args
|
106 |
+
if n in (S.Zero, S.NegativeOne):
|
107 |
+
return self.func(x, a, n-1)
|
108 |
+
elif n.is_positive:
|
109 |
+
return n*self.func(x, a, n-1)
|
110 |
+
else:
|
111 |
+
raise ArgumentIndexError(self, argindex)
|
112 |
+
|
113 |
+
@classmethod
|
114 |
+
def eval(cls, variable, offset, exponent):
|
115 |
+
"""
|
116 |
+
Returns a simplified form or a value of Singularity Function depending
|
117 |
+
on the argument passed by the object.
|
118 |
+
|
119 |
+
Explanation
|
120 |
+
===========
|
121 |
+
|
122 |
+
The ``eval()`` method is automatically called when the
|
123 |
+
``SingularityFunction`` class is about to be instantiated and it
|
124 |
+
returns either some simplified instance or the unevaluated instance
|
125 |
+
depending on the argument passed. In other words, ``eval()`` method is
|
126 |
+
not needed to be called explicitly, it is being called and evaluated
|
127 |
+
once the object is called.
|
128 |
+
|
129 |
+
Examples
|
130 |
+
========
|
131 |
+
|
132 |
+
>>> from sympy import SingularityFunction, Symbol, nan
|
133 |
+
>>> from sympy.abc import x, a, n
|
134 |
+
>>> SingularityFunction(x, a, n)
|
135 |
+
SingularityFunction(x, a, n)
|
136 |
+
>>> SingularityFunction(5, 3, 2)
|
137 |
+
4
|
138 |
+
>>> SingularityFunction(x, a, nan)
|
139 |
+
nan
|
140 |
+
>>> SingularityFunction(x, 3, 0).subs(x, 3)
|
141 |
+
1
|
142 |
+
>>> SingularityFunction(4, 1, 5)
|
143 |
+
243
|
144 |
+
>>> x = Symbol('x', positive = True)
|
145 |
+
>>> a = Symbol('a', negative = True)
|
146 |
+
>>> n = Symbol('n', nonnegative = True)
|
147 |
+
>>> SingularityFunction(x, a, n)
|
148 |
+
(-a + x)**n
|
149 |
+
>>> x = Symbol('x', negative = True)
|
150 |
+
>>> a = Symbol('a', positive = True)
|
151 |
+
>>> SingularityFunction(x, a, n)
|
152 |
+
0
|
153 |
+
|
154 |
+
"""
|
155 |
+
|
156 |
+
x = variable
|
157 |
+
a = offset
|
158 |
+
n = exponent
|
159 |
+
shift = (x - a)
|
160 |
+
|
161 |
+
if fuzzy_not(im(shift).is_zero):
|
162 |
+
raise ValueError("Singularity Functions are defined only for Real Numbers.")
|
163 |
+
if fuzzy_not(im(n).is_zero):
|
164 |
+
raise ValueError("Singularity Functions are not defined for imaginary exponents.")
|
165 |
+
if shift is S.NaN or n is S.NaN:
|
166 |
+
return S.NaN
|
167 |
+
if (n + 2).is_negative:
|
168 |
+
raise ValueError("Singularity Functions are not defined for exponents less than -2.")
|
169 |
+
if shift.is_extended_negative:
|
170 |
+
return S.Zero
|
171 |
+
if n.is_nonnegative and shift.is_extended_nonnegative:
|
172 |
+
return (x - a)**n
|
173 |
+
if n in (S.NegativeOne, -2):
|
174 |
+
if shift.is_negative or shift.is_extended_positive:
|
175 |
+
return S.Zero
|
176 |
+
if shift.is_zero:
|
177 |
+
return oo
|
178 |
+
|
179 |
+
def _eval_rewrite_as_Piecewise(self, *args, **kwargs):
|
180 |
+
'''
|
181 |
+
Converts a Singularity Function expression into its Piecewise form.
|
182 |
+
|
183 |
+
'''
|
184 |
+
x, a, n = self.args
|
185 |
+
|
186 |
+
if n in (S.NegativeOne, S(-2)):
|
187 |
+
return Piecewise((oo, Eq((x - a), 0)), (0, True))
|
188 |
+
elif n.is_nonnegative:
|
189 |
+
return Piecewise(((x - a)**n, (x - a) > 0), (0, True))
|
190 |
+
|
191 |
+
def _eval_rewrite_as_Heaviside(self, *args, **kwargs):
|
192 |
+
'''
|
193 |
+
Rewrites a Singularity Function expression using Heavisides and DiracDeltas.
|
194 |
+
|
195 |
+
'''
|
196 |
+
x, a, n = self.args
|
197 |
+
|
198 |
+
if n == -2:
|
199 |
+
return diff(Heaviside(x - a), x.free_symbols.pop(), 2)
|
200 |
+
if n == -1:
|
201 |
+
return diff(Heaviside(x - a), x.free_symbols.pop(), 1)
|
202 |
+
if n.is_nonnegative:
|
203 |
+
return (x - a)**n*Heaviside(x - a)
|
204 |
+
|
205 |
+
def _eval_as_leading_term(self, x, logx=None, cdir=0):
|
206 |
+
z, a, n = self.args
|
207 |
+
shift = (z - a).subs(x, 0)
|
208 |
+
if n < 0:
|
209 |
+
return S.Zero
|
210 |
+
elif n.is_zero and shift.is_zero:
|
211 |
+
return S.Zero if cdir == -1 else S.One
|
212 |
+
elif shift.is_positive:
|
213 |
+
return shift**n
|
214 |
+
return S.Zero
|
215 |
+
|
216 |
+
def _eval_nseries(self, x, n, logx=None, cdir=0):
|
217 |
+
z, a, n = self.args
|
218 |
+
shift = (z - a).subs(x, 0)
|
219 |
+
if n < 0:
|
220 |
+
return S.Zero
|
221 |
+
elif n.is_zero and shift.is_zero:
|
222 |
+
return S.Zero if cdir == -1 else S.One
|
223 |
+
elif shift.is_positive:
|
224 |
+
return ((z - a)**n)._eval_nseries(x, n, logx=logx, cdir=cdir)
|
225 |
+
return S.Zero
|
226 |
+
|
227 |
+
_eval_rewrite_as_DiracDelta = _eval_rewrite_as_Heaviside
|
228 |
+
_eval_rewrite_as_HeavisideDiracDelta = _eval_rewrite_as_Heaviside
|
venv/lib/python3.10/site-packages/sympy/functions/special/spherical_harmonics.py
ADDED
@@ -0,0 +1,334 @@
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|
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|
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|
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|
|
|
|
|
|
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|
|
|
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|
|
|
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|
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|
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|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
1 |
+
from sympy.core.expr import Expr
|
2 |
+
from sympy.core.function import Function, ArgumentIndexError
|
3 |
+
from sympy.core.numbers import I, pi
|
4 |
+
from sympy.core.singleton import S
|
5 |
+
from sympy.core.symbol import Dummy
|
6 |
+
from sympy.functions import assoc_legendre
|
7 |
+
from sympy.functions.combinatorial.factorials import factorial
|
8 |
+
from sympy.functions.elementary.complexes import Abs, conjugate
|
9 |
+
from sympy.functions.elementary.exponential import exp
|
10 |
+
from sympy.functions.elementary.miscellaneous import sqrt
|
11 |
+
from sympy.functions.elementary.trigonometric import sin, cos, cot
|
12 |
+
|
13 |
+
_x = Dummy("x")
|
14 |
+
|
15 |
+
class Ynm(Function):
|
16 |
+
r"""
|
17 |
+
Spherical harmonics defined as
|
18 |
+
|
19 |
+
.. math::
|
20 |
+
Y_n^m(\theta, \varphi) := \sqrt{\frac{(2n+1)(n-m)!}{4\pi(n+m)!}}
|
21 |
+
\exp(i m \varphi)
|
22 |
+
\mathrm{P}_n^m\left(\cos(\theta)\right)
|
23 |
+
|
24 |
+
Explanation
|
25 |
+
===========
|
26 |
+
|
27 |
+
``Ynm()`` gives the spherical harmonic function of order $n$ and $m$
|
28 |
+
in $\theta$ and $\varphi$, $Y_n^m(\theta, \varphi)$. The four
|
29 |
+
parameters are as follows: $n \geq 0$ an integer and $m$ an integer
|
30 |
+
such that $-n \leq m \leq n$ holds. The two angles are real-valued
|
31 |
+
with $\theta \in [0, \pi]$ and $\varphi \in [0, 2\pi]$.
|
32 |
+
|
33 |
+
Examples
|
34 |
+
========
|
35 |
+
|
36 |
+
>>> from sympy import Ynm, Symbol, simplify
|
37 |
+
>>> from sympy.abc import n,m
|
38 |
+
>>> theta = Symbol("theta")
|
39 |
+
>>> phi = Symbol("phi")
|
40 |
+
|
41 |
+
>>> Ynm(n, m, theta, phi)
|
42 |
+
Ynm(n, m, theta, phi)
|
43 |
+
|
44 |
+
Several symmetries are known, for the order:
|
45 |
+
|
46 |
+
>>> Ynm(n, -m, theta, phi)
|
47 |
+
(-1)**m*exp(-2*I*m*phi)*Ynm(n, m, theta, phi)
|
48 |
+
|
49 |
+
As well as for the angles:
|
50 |
+
|
51 |
+
>>> Ynm(n, m, -theta, phi)
|
52 |
+
Ynm(n, m, theta, phi)
|
53 |
+
|
54 |
+
>>> Ynm(n, m, theta, -phi)
|
55 |
+
exp(-2*I*m*phi)*Ynm(n, m, theta, phi)
|
56 |
+
|
57 |
+
For specific integers $n$ and $m$ we can evaluate the harmonics
|
58 |
+
to more useful expressions:
|
59 |
+
|
60 |
+
>>> simplify(Ynm(0, 0, theta, phi).expand(func=True))
|
61 |
+
1/(2*sqrt(pi))
|
62 |
+
|
63 |
+
>>> simplify(Ynm(1, -1, theta, phi).expand(func=True))
|
64 |
+
sqrt(6)*exp(-I*phi)*sin(theta)/(4*sqrt(pi))
|
65 |
+
|
66 |
+
>>> simplify(Ynm(1, 0, theta, phi).expand(func=True))
|
67 |
+
sqrt(3)*cos(theta)/(2*sqrt(pi))
|
68 |
+
|
69 |
+
>>> simplify(Ynm(1, 1, theta, phi).expand(func=True))
|
70 |
+
-sqrt(6)*exp(I*phi)*sin(theta)/(4*sqrt(pi))
|
71 |
+
|
72 |
+
>>> simplify(Ynm(2, -2, theta, phi).expand(func=True))
|
73 |
+
sqrt(30)*exp(-2*I*phi)*sin(theta)**2/(8*sqrt(pi))
|
74 |
+
|
75 |
+
>>> simplify(Ynm(2, -1, theta, phi).expand(func=True))
|
76 |
+
sqrt(30)*exp(-I*phi)*sin(2*theta)/(8*sqrt(pi))
|
77 |
+
|
78 |
+
>>> simplify(Ynm(2, 0, theta, phi).expand(func=True))
|
79 |
+
sqrt(5)*(3*cos(theta)**2 - 1)/(4*sqrt(pi))
|
80 |
+
|
81 |
+
>>> simplify(Ynm(2, 1, theta, phi).expand(func=True))
|
82 |
+
-sqrt(30)*exp(I*phi)*sin(2*theta)/(8*sqrt(pi))
|
83 |
+
|
84 |
+
>>> simplify(Ynm(2, 2, theta, phi).expand(func=True))
|
85 |
+
sqrt(30)*exp(2*I*phi)*sin(theta)**2/(8*sqrt(pi))
|
86 |
+
|
87 |
+
We can differentiate the functions with respect
|
88 |
+
to both angles:
|
89 |
+
|
90 |
+
>>> from sympy import Ynm, Symbol, diff
|
91 |
+
>>> from sympy.abc import n,m
|
92 |
+
>>> theta = Symbol("theta")
|
93 |
+
>>> phi = Symbol("phi")
|
94 |
+
|
95 |
+
>>> diff(Ynm(n, m, theta, phi), theta)
|
96 |
+
m*cot(theta)*Ynm(n, m, theta, phi) + sqrt((-m + n)*(m + n + 1))*exp(-I*phi)*Ynm(n, m + 1, theta, phi)
|
97 |
+
|
98 |
+
>>> diff(Ynm(n, m, theta, phi), phi)
|
99 |
+
I*m*Ynm(n, m, theta, phi)
|
100 |
+
|
101 |
+
Further we can compute the complex conjugation:
|
102 |
+
|
103 |
+
>>> from sympy import Ynm, Symbol, conjugate
|
104 |
+
>>> from sympy.abc import n,m
|
105 |
+
>>> theta = Symbol("theta")
|
106 |
+
>>> phi = Symbol("phi")
|
107 |
+
|
108 |
+
>>> conjugate(Ynm(n, m, theta, phi))
|
109 |
+
(-1)**(2*m)*exp(-2*I*m*phi)*Ynm(n, m, theta, phi)
|
110 |
+
|
111 |
+
To get back the well known expressions in spherical
|
112 |
+
coordinates, we use full expansion:
|
113 |
+
|
114 |
+
>>> from sympy import Ynm, Symbol, expand_func
|
115 |
+
>>> from sympy.abc import n,m
|
116 |
+
>>> theta = Symbol("theta")
|
117 |
+
>>> phi = Symbol("phi")
|
118 |
+
|
119 |
+
>>> expand_func(Ynm(n, m, theta, phi))
|
120 |
+
sqrt((2*n + 1)*factorial(-m + n)/factorial(m + n))*exp(I*m*phi)*assoc_legendre(n, m, cos(theta))/(2*sqrt(pi))
|
121 |
+
|
122 |
+
See Also
|
123 |
+
========
|
124 |
+
|
125 |
+
Ynm_c, Znm
|
126 |
+
|
127 |
+
References
|
128 |
+
==========
|
129 |
+
|
130 |
+
.. [1] https://en.wikipedia.org/wiki/Spherical_harmonics
|
131 |
+
.. [2] https://mathworld.wolfram.com/SphericalHarmonic.html
|
132 |
+
.. [3] https://functions.wolfram.com/Polynomials/SphericalHarmonicY/
|
133 |
+
.. [4] https://dlmf.nist.gov/14.30
|
134 |
+
|
135 |
+
"""
|
136 |
+
|
137 |
+
@classmethod
|
138 |
+
def eval(cls, n, m, theta, phi):
|
139 |
+
# Handle negative index m and arguments theta, phi
|
140 |
+
if m.could_extract_minus_sign():
|
141 |
+
m = -m
|
142 |
+
return S.NegativeOne**m * exp(-2*I*m*phi) * Ynm(n, m, theta, phi)
|
143 |
+
if theta.could_extract_minus_sign():
|
144 |
+
theta = -theta
|
145 |
+
return Ynm(n, m, theta, phi)
|
146 |
+
if phi.could_extract_minus_sign():
|
147 |
+
phi = -phi
|
148 |
+
return exp(-2*I*m*phi) * Ynm(n, m, theta, phi)
|
149 |
+
|
150 |
+
# TODO Add more simplififcation here
|
151 |
+
|
152 |
+
def _eval_expand_func(self, **hints):
|
153 |
+
n, m, theta, phi = self.args
|
154 |
+
rv = (sqrt((2*n + 1)/(4*pi) * factorial(n - m)/factorial(n + m)) *
|
155 |
+
exp(I*m*phi) * assoc_legendre(n, m, cos(theta)))
|
156 |
+
# We can do this because of the range of theta
|
157 |
+
return rv.subs(sqrt(-cos(theta)**2 + 1), sin(theta))
|
158 |
+
|
159 |
+
def fdiff(self, argindex=4):
|
160 |
+
if argindex == 1:
|
161 |
+
# Diff wrt n
|
162 |
+
raise ArgumentIndexError(self, argindex)
|
163 |
+
elif argindex == 2:
|
164 |
+
# Diff wrt m
|
165 |
+
raise ArgumentIndexError(self, argindex)
|
166 |
+
elif argindex == 3:
|
167 |
+
# Diff wrt theta
|
168 |
+
n, m, theta, phi = self.args
|
169 |
+
return (m * cot(theta) * Ynm(n, m, theta, phi) +
|
170 |
+
sqrt((n - m)*(n + m + 1)) * exp(-I*phi) * Ynm(n, m + 1, theta, phi))
|
171 |
+
elif argindex == 4:
|
172 |
+
# Diff wrt phi
|
173 |
+
n, m, theta, phi = self.args
|
174 |
+
return I * m * Ynm(n, m, theta, phi)
|
175 |
+
else:
|
176 |
+
raise ArgumentIndexError(self, argindex)
|
177 |
+
|
178 |
+
def _eval_rewrite_as_polynomial(self, n, m, theta, phi, **kwargs):
|
179 |
+
# TODO: Make sure n \in N
|
180 |
+
# TODO: Assert |m| <= n ortherwise we should return 0
|
181 |
+
return self.expand(func=True)
|
182 |
+
|
183 |
+
def _eval_rewrite_as_sin(self, n, m, theta, phi, **kwargs):
|
184 |
+
return self.rewrite(cos)
|
185 |
+
|
186 |
+
def _eval_rewrite_as_cos(self, n, m, theta, phi, **kwargs):
|
187 |
+
# This method can be expensive due to extensive use of simplification!
|
188 |
+
from sympy.simplify import simplify, trigsimp
|
189 |
+
# TODO: Make sure n \in N
|
190 |
+
# TODO: Assert |m| <= n ortherwise we should return 0
|
191 |
+
term = simplify(self.expand(func=True))
|
192 |
+
# We can do this because of the range of theta
|
193 |
+
term = term.xreplace({Abs(sin(theta)):sin(theta)})
|
194 |
+
return simplify(trigsimp(term))
|
195 |
+
|
196 |
+
def _eval_conjugate(self):
|
197 |
+
# TODO: Make sure theta \in R and phi \in R
|
198 |
+
n, m, theta, phi = self.args
|
199 |
+
return S.NegativeOne**m * self.func(n, -m, theta, phi)
|
200 |
+
|
201 |
+
def as_real_imag(self, deep=True, **hints):
|
202 |
+
# TODO: Handle deep and hints
|
203 |
+
n, m, theta, phi = self.args
|
204 |
+
re = (sqrt((2*n + 1)/(4*pi) * factorial(n - m)/factorial(n + m)) *
|
205 |
+
cos(m*phi) * assoc_legendre(n, m, cos(theta)))
|
206 |
+
im = (sqrt((2*n + 1)/(4*pi) * factorial(n - m)/factorial(n + m)) *
|
207 |
+
sin(m*phi) * assoc_legendre(n, m, cos(theta)))
|
208 |
+
return (re, im)
|
209 |
+
|
210 |
+
def _eval_evalf(self, prec):
|
211 |
+
# Note: works without this function by just calling
|
212 |
+
# mpmath for Legendre polynomials. But using
|
213 |
+
# the dedicated function directly is cleaner.
|
214 |
+
from mpmath import mp, workprec
|
215 |
+
n = self.args[0]._to_mpmath(prec)
|
216 |
+
m = self.args[1]._to_mpmath(prec)
|
217 |
+
theta = self.args[2]._to_mpmath(prec)
|
218 |
+
phi = self.args[3]._to_mpmath(prec)
|
219 |
+
with workprec(prec):
|
220 |
+
res = mp.spherharm(n, m, theta, phi)
|
221 |
+
return Expr._from_mpmath(res, prec)
|
222 |
+
|
223 |
+
|
224 |
+
def Ynm_c(n, m, theta, phi):
|
225 |
+
r"""
|
226 |
+
Conjugate spherical harmonics defined as
|
227 |
+
|
228 |
+
.. math::
|
229 |
+
\overline{Y_n^m(\theta, \varphi)} := (-1)^m Y_n^{-m}(\theta, \varphi).
|
230 |
+
|
231 |
+
Examples
|
232 |
+
========
|
233 |
+
|
234 |
+
>>> from sympy import Ynm_c, Symbol, simplify
|
235 |
+
>>> from sympy.abc import n,m
|
236 |
+
>>> theta = Symbol("theta")
|
237 |
+
>>> phi = Symbol("phi")
|
238 |
+
>>> Ynm_c(n, m, theta, phi)
|
239 |
+
(-1)**(2*m)*exp(-2*I*m*phi)*Ynm(n, m, theta, phi)
|
240 |
+
>>> Ynm_c(n, m, -theta, phi)
|
241 |
+
(-1)**(2*m)*exp(-2*I*m*phi)*Ynm(n, m, theta, phi)
|
242 |
+
|
243 |
+
For specific integers $n$ and $m$ we can evaluate the harmonics
|
244 |
+
to more useful expressions:
|
245 |
+
|
246 |
+
>>> simplify(Ynm_c(0, 0, theta, phi).expand(func=True))
|
247 |
+
1/(2*sqrt(pi))
|
248 |
+
>>> simplify(Ynm_c(1, -1, theta, phi).expand(func=True))
|
249 |
+
sqrt(6)*exp(I*(-phi + 2*conjugate(phi)))*sin(theta)/(4*sqrt(pi))
|
250 |
+
|
251 |
+
See Also
|
252 |
+
========
|
253 |
+
|
254 |
+
Ynm, Znm
|
255 |
+
|
256 |
+
References
|
257 |
+
==========
|
258 |
+
|
259 |
+
.. [1] https://en.wikipedia.org/wiki/Spherical_harmonics
|
260 |
+
.. [2] https://mathworld.wolfram.com/SphericalHarmonic.html
|
261 |
+
.. [3] https://functions.wolfram.com/Polynomials/SphericalHarmonicY/
|
262 |
+
|
263 |
+
"""
|
264 |
+
return conjugate(Ynm(n, m, theta, phi))
|
265 |
+
|
266 |
+
|
267 |
+
class Znm(Function):
|
268 |
+
r"""
|
269 |
+
Real spherical harmonics defined as
|
270 |
+
|
271 |
+
.. math::
|
272 |
+
|
273 |
+
Z_n^m(\theta, \varphi) :=
|
274 |
+
\begin{cases}
|
275 |
+
\frac{Y_n^m(\theta, \varphi) + \overline{Y_n^m(\theta, \varphi)}}{\sqrt{2}} &\quad m > 0 \\
|
276 |
+
Y_n^m(\theta, \varphi) &\quad m = 0 \\
|
277 |
+
\frac{Y_n^m(\theta, \varphi) - \overline{Y_n^m(\theta, \varphi)}}{i \sqrt{2}} &\quad m < 0 \\
|
278 |
+
\end{cases}
|
279 |
+
|
280 |
+
which gives in simplified form
|
281 |
+
|
282 |
+
.. math::
|
283 |
+
|
284 |
+
Z_n^m(\theta, \varphi) =
|
285 |
+
\begin{cases}
|
286 |
+
\frac{Y_n^m(\theta, \varphi) + (-1)^m Y_n^{-m}(\theta, \varphi)}{\sqrt{2}} &\quad m > 0 \\
|
287 |
+
Y_n^m(\theta, \varphi) &\quad m = 0 \\
|
288 |
+
\frac{Y_n^m(\theta, \varphi) - (-1)^m Y_n^{-m}(\theta, \varphi)}{i \sqrt{2}} &\quad m < 0 \\
|
289 |
+
\end{cases}
|
290 |
+
|
291 |
+
Examples
|
292 |
+
========
|
293 |
+
|
294 |
+
>>> from sympy import Znm, Symbol, simplify
|
295 |
+
>>> from sympy.abc import n, m
|
296 |
+
>>> theta = Symbol("theta")
|
297 |
+
>>> phi = Symbol("phi")
|
298 |
+
>>> Znm(n, m, theta, phi)
|
299 |
+
Znm(n, m, theta, phi)
|
300 |
+
|
301 |
+
For specific integers n and m we can evaluate the harmonics
|
302 |
+
to more useful expressions:
|
303 |
+
|
304 |
+
>>> simplify(Znm(0, 0, theta, phi).expand(func=True))
|
305 |
+
1/(2*sqrt(pi))
|
306 |
+
>>> simplify(Znm(1, 1, theta, phi).expand(func=True))
|
307 |
+
-sqrt(3)*sin(theta)*cos(phi)/(2*sqrt(pi))
|
308 |
+
>>> simplify(Znm(2, 1, theta, phi).expand(func=True))
|
309 |
+
-sqrt(15)*sin(2*theta)*cos(phi)/(4*sqrt(pi))
|
310 |
+
|
311 |
+
See Also
|
312 |
+
========
|
313 |
+
|
314 |
+
Ynm, Ynm_c
|
315 |
+
|
316 |
+
References
|
317 |
+
==========
|
318 |
+
|
319 |
+
.. [1] https://en.wikipedia.org/wiki/Spherical_harmonics
|
320 |
+
.. [2] https://mathworld.wolfram.com/SphericalHarmonic.html
|
321 |
+
.. [3] https://functions.wolfram.com/Polynomials/SphericalHarmonicY/
|
322 |
+
|
323 |
+
"""
|
324 |
+
|
325 |
+
@classmethod
|
326 |
+
def eval(cls, n, m, theta, phi):
|
327 |
+
if m.is_positive:
|
328 |
+
zz = (Ynm(n, m, theta, phi) + Ynm_c(n, m, theta, phi)) / sqrt(2)
|
329 |
+
return zz
|
330 |
+
elif m.is_zero:
|
331 |
+
return Ynm(n, m, theta, phi)
|
332 |
+
elif m.is_negative:
|
333 |
+
zz = (Ynm(n, m, theta, phi) - Ynm_c(n, m, theta, phi)) / (sqrt(2)*I)
|
334 |
+
return zz
|
venv/lib/python3.10/site-packages/sympy/functions/special/tensor_functions.py
ADDED
@@ -0,0 +1,474 @@
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|
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|
|
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|
|
|
|
|
|
|
|
|
|
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|
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|
|
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|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
1 |
+
from math import prod
|
2 |
+
|
3 |
+
from sympy.core import S, Integer
|
4 |
+
from sympy.core.function import Function
|
5 |
+
from sympy.core.logic import fuzzy_not
|
6 |
+
from sympy.core.relational import Ne
|
7 |
+
from sympy.core.sorting import default_sort_key
|
8 |
+
from sympy.external.gmpy import SYMPY_INTS
|
9 |
+
from sympy.functions.combinatorial.factorials import factorial
|
10 |
+
from sympy.functions.elementary.piecewise import Piecewise
|
11 |
+
from sympy.utilities.iterables import has_dups
|
12 |
+
|
13 |
+
###############################################################################
|
14 |
+
###################### Kronecker Delta, Levi-Civita etc. ######################
|
15 |
+
###############################################################################
|
16 |
+
|
17 |
+
|
18 |
+
def Eijk(*args, **kwargs):
|
19 |
+
"""
|
20 |
+
Represent the Levi-Civita symbol.
|
21 |
+
|
22 |
+
This is a compatibility wrapper to ``LeviCivita()``.
|
23 |
+
|
24 |
+
See Also
|
25 |
+
========
|
26 |
+
|
27 |
+
LeviCivita
|
28 |
+
|
29 |
+
"""
|
30 |
+
return LeviCivita(*args, **kwargs)
|
31 |
+
|
32 |
+
|
33 |
+
def eval_levicivita(*args):
|
34 |
+
"""Evaluate Levi-Civita symbol."""
|
35 |
+
n = len(args)
|
36 |
+
return prod(
|
37 |
+
prod(args[j] - args[i] for j in range(i + 1, n))
|
38 |
+
/ factorial(i) for i in range(n))
|
39 |
+
# converting factorial(i) to int is slightly faster
|
40 |
+
|
41 |
+
|
42 |
+
class LeviCivita(Function):
|
43 |
+
"""
|
44 |
+
Represent the Levi-Civita symbol.
|
45 |
+
|
46 |
+
Explanation
|
47 |
+
===========
|
48 |
+
|
49 |
+
For even permutations of indices it returns 1, for odd permutations -1, and
|
50 |
+
for everything else (a repeated index) it returns 0.
|
51 |
+
|
52 |
+
Thus it represents an alternating pseudotensor.
|
53 |
+
|
54 |
+
Examples
|
55 |
+
========
|
56 |
+
|
57 |
+
>>> from sympy import LeviCivita
|
58 |
+
>>> from sympy.abc import i, j, k
|
59 |
+
>>> LeviCivita(1, 2, 3)
|
60 |
+
1
|
61 |
+
>>> LeviCivita(1, 3, 2)
|
62 |
+
-1
|
63 |
+
>>> LeviCivita(1, 2, 2)
|
64 |
+
0
|
65 |
+
>>> LeviCivita(i, j, k)
|
66 |
+
LeviCivita(i, j, k)
|
67 |
+
>>> LeviCivita(i, j, i)
|
68 |
+
0
|
69 |
+
|
70 |
+
See Also
|
71 |
+
========
|
72 |
+
|
73 |
+
Eijk
|
74 |
+
|
75 |
+
"""
|
76 |
+
|
77 |
+
is_integer = True
|
78 |
+
|
79 |
+
@classmethod
|
80 |
+
def eval(cls, *args):
|
81 |
+
if all(isinstance(a, (SYMPY_INTS, Integer)) for a in args):
|
82 |
+
return eval_levicivita(*args)
|
83 |
+
if has_dups(args):
|
84 |
+
return S.Zero
|
85 |
+
|
86 |
+
def doit(self, **hints):
|
87 |
+
return eval_levicivita(*self.args)
|
88 |
+
|
89 |
+
|
90 |
+
class KroneckerDelta(Function):
|
91 |
+
"""
|
92 |
+
The discrete, or Kronecker, delta function.
|
93 |
+
|
94 |
+
Explanation
|
95 |
+
===========
|
96 |
+
|
97 |
+
A function that takes in two integers $i$ and $j$. It returns $0$ if $i$
|
98 |
+
and $j$ are not equal, or it returns $1$ if $i$ and $j$ are equal.
|
99 |
+
|
100 |
+
Examples
|
101 |
+
========
|
102 |
+
|
103 |
+
An example with integer indices:
|
104 |
+
|
105 |
+
>>> from sympy import KroneckerDelta
|
106 |
+
>>> KroneckerDelta(1, 2)
|
107 |
+
0
|
108 |
+
>>> KroneckerDelta(3, 3)
|
109 |
+
1
|
110 |
+
|
111 |
+
Symbolic indices:
|
112 |
+
|
113 |
+
>>> from sympy.abc import i, j, k
|
114 |
+
>>> KroneckerDelta(i, j)
|
115 |
+
KroneckerDelta(i, j)
|
116 |
+
>>> KroneckerDelta(i, i)
|
117 |
+
1
|
118 |
+
>>> KroneckerDelta(i, i + 1)
|
119 |
+
0
|
120 |
+
>>> KroneckerDelta(i, i + 1 + k)
|
121 |
+
KroneckerDelta(i, i + k + 1)
|
122 |
+
|
123 |
+
Parameters
|
124 |
+
==========
|
125 |
+
|
126 |
+
i : Number, Symbol
|
127 |
+
The first index of the delta function.
|
128 |
+
j : Number, Symbol
|
129 |
+
The second index of the delta function.
|
130 |
+
|
131 |
+
See Also
|
132 |
+
========
|
133 |
+
|
134 |
+
eval
|
135 |
+
DiracDelta
|
136 |
+
|
137 |
+
References
|
138 |
+
==========
|
139 |
+
|
140 |
+
.. [1] https://en.wikipedia.org/wiki/Kronecker_delta
|
141 |
+
|
142 |
+
"""
|
143 |
+
|
144 |
+
is_integer = True
|
145 |
+
|
146 |
+
@classmethod
|
147 |
+
def eval(cls, i, j, delta_range=None):
|
148 |
+
"""
|
149 |
+
Evaluates the discrete delta function.
|
150 |
+
|
151 |
+
Examples
|
152 |
+
========
|
153 |
+
|
154 |
+
>>> from sympy import KroneckerDelta
|
155 |
+
>>> from sympy.abc import i, j, k
|
156 |
+
|
157 |
+
>>> KroneckerDelta(i, j)
|
158 |
+
KroneckerDelta(i, j)
|
159 |
+
>>> KroneckerDelta(i, i)
|
160 |
+
1
|
161 |
+
>>> KroneckerDelta(i, i + 1)
|
162 |
+
0
|
163 |
+
>>> KroneckerDelta(i, i + 1 + k)
|
164 |
+
KroneckerDelta(i, i + k + 1)
|
165 |
+
|
166 |
+
# indirect doctest
|
167 |
+
|
168 |
+
"""
|
169 |
+
|
170 |
+
if delta_range is not None:
|
171 |
+
dinf, dsup = delta_range
|
172 |
+
if (dinf - i > 0) == True:
|
173 |
+
return S.Zero
|
174 |
+
if (dinf - j > 0) == True:
|
175 |
+
return S.Zero
|
176 |
+
if (dsup - i < 0) == True:
|
177 |
+
return S.Zero
|
178 |
+
if (dsup - j < 0) == True:
|
179 |
+
return S.Zero
|
180 |
+
|
181 |
+
diff = i - j
|
182 |
+
if diff.is_zero:
|
183 |
+
return S.One
|
184 |
+
elif fuzzy_not(diff.is_zero):
|
185 |
+
return S.Zero
|
186 |
+
|
187 |
+
if i.assumptions0.get("below_fermi") and \
|
188 |
+
j.assumptions0.get("above_fermi"):
|
189 |
+
return S.Zero
|
190 |
+
if j.assumptions0.get("below_fermi") and \
|
191 |
+
i.assumptions0.get("above_fermi"):
|
192 |
+
return S.Zero
|
193 |
+
# to make KroneckerDelta canonical
|
194 |
+
# following lines will check if inputs are in order
|
195 |
+
# if not, will return KroneckerDelta with correct order
|
196 |
+
if i != min(i, j, key=default_sort_key):
|
197 |
+
if delta_range:
|
198 |
+
return cls(j, i, delta_range)
|
199 |
+
else:
|
200 |
+
return cls(j, i)
|
201 |
+
|
202 |
+
@property
|
203 |
+
def delta_range(self):
|
204 |
+
if len(self.args) > 2:
|
205 |
+
return self.args[2]
|
206 |
+
|
207 |
+
def _eval_power(self, expt):
|
208 |
+
if expt.is_positive:
|
209 |
+
return self
|
210 |
+
if expt.is_negative and expt is not S.NegativeOne:
|
211 |
+
return 1/self
|
212 |
+
|
213 |
+
@property
|
214 |
+
def is_above_fermi(self):
|
215 |
+
"""
|
216 |
+
True if Delta can be non-zero above fermi.
|
217 |
+
|
218 |
+
Examples
|
219 |
+
========
|
220 |
+
|
221 |
+
>>> from sympy import KroneckerDelta, Symbol
|
222 |
+
>>> a = Symbol('a', above_fermi=True)
|
223 |
+
>>> i = Symbol('i', below_fermi=True)
|
224 |
+
>>> p = Symbol('p')
|
225 |
+
>>> q = Symbol('q')
|
226 |
+
>>> KroneckerDelta(p, a).is_above_fermi
|
227 |
+
True
|
228 |
+
>>> KroneckerDelta(p, i).is_above_fermi
|
229 |
+
False
|
230 |
+
>>> KroneckerDelta(p, q).is_above_fermi
|
231 |
+
True
|
232 |
+
|
233 |
+
See Also
|
234 |
+
========
|
235 |
+
|
236 |
+
is_below_fermi, is_only_below_fermi, is_only_above_fermi
|
237 |
+
|
238 |
+
"""
|
239 |
+
if self.args[0].assumptions0.get("below_fermi"):
|
240 |
+
return False
|
241 |
+
if self.args[1].assumptions0.get("below_fermi"):
|
242 |
+
return False
|
243 |
+
return True
|
244 |
+
|
245 |
+
@property
|
246 |
+
def is_below_fermi(self):
|
247 |
+
"""
|
248 |
+
True if Delta can be non-zero below fermi.
|
249 |
+
|
250 |
+
Examples
|
251 |
+
========
|
252 |
+
|
253 |
+
>>> from sympy import KroneckerDelta, Symbol
|
254 |
+
>>> a = Symbol('a', above_fermi=True)
|
255 |
+
>>> i = Symbol('i', below_fermi=True)
|
256 |
+
>>> p = Symbol('p')
|
257 |
+
>>> q = Symbol('q')
|
258 |
+
>>> KroneckerDelta(p, a).is_below_fermi
|
259 |
+
False
|
260 |
+
>>> KroneckerDelta(p, i).is_below_fermi
|
261 |
+
True
|
262 |
+
>>> KroneckerDelta(p, q).is_below_fermi
|
263 |
+
True
|
264 |
+
|
265 |
+
See Also
|
266 |
+
========
|
267 |
+
|
268 |
+
is_above_fermi, is_only_above_fermi, is_only_below_fermi
|
269 |
+
|
270 |
+
"""
|
271 |
+
if self.args[0].assumptions0.get("above_fermi"):
|
272 |
+
return False
|
273 |
+
if self.args[1].assumptions0.get("above_fermi"):
|
274 |
+
return False
|
275 |
+
return True
|
276 |
+
|
277 |
+
@property
|
278 |
+
def is_only_above_fermi(self):
|
279 |
+
"""
|
280 |
+
True if Delta is restricted to above fermi.
|
281 |
+
|
282 |
+
Examples
|
283 |
+
========
|
284 |
+
|
285 |
+
>>> from sympy import KroneckerDelta, Symbol
|
286 |
+
>>> a = Symbol('a', above_fermi=True)
|
287 |
+
>>> i = Symbol('i', below_fermi=True)
|
288 |
+
>>> p = Symbol('p')
|
289 |
+
>>> q = Symbol('q')
|
290 |
+
>>> KroneckerDelta(p, a).is_only_above_fermi
|
291 |
+
True
|
292 |
+
>>> KroneckerDelta(p, q).is_only_above_fermi
|
293 |
+
False
|
294 |
+
>>> KroneckerDelta(p, i).is_only_above_fermi
|
295 |
+
False
|
296 |
+
|
297 |
+
See Also
|
298 |
+
========
|
299 |
+
|
300 |
+
is_above_fermi, is_below_fermi, is_only_below_fermi
|
301 |
+
|
302 |
+
"""
|
303 |
+
return ( self.args[0].assumptions0.get("above_fermi")
|
304 |
+
or
|
305 |
+
self.args[1].assumptions0.get("above_fermi")
|
306 |
+
) or False
|
307 |
+
|
308 |
+
@property
|
309 |
+
def is_only_below_fermi(self):
|
310 |
+
"""
|
311 |
+
True if Delta is restricted to below fermi.
|
312 |
+
|
313 |
+
Examples
|
314 |
+
========
|
315 |
+
|
316 |
+
>>> from sympy import KroneckerDelta, Symbol
|
317 |
+
>>> a = Symbol('a', above_fermi=True)
|
318 |
+
>>> i = Symbol('i', below_fermi=True)
|
319 |
+
>>> p = Symbol('p')
|
320 |
+
>>> q = Symbol('q')
|
321 |
+
>>> KroneckerDelta(p, i).is_only_below_fermi
|
322 |
+
True
|
323 |
+
>>> KroneckerDelta(p, q).is_only_below_fermi
|
324 |
+
False
|
325 |
+
>>> KroneckerDelta(p, a).is_only_below_fermi
|
326 |
+
False
|
327 |
+
|
328 |
+
See Also
|
329 |
+
========
|
330 |
+
|
331 |
+
is_above_fermi, is_below_fermi, is_only_above_fermi
|
332 |
+
|
333 |
+
"""
|
334 |
+
return ( self.args[0].assumptions0.get("below_fermi")
|
335 |
+
or
|
336 |
+
self.args[1].assumptions0.get("below_fermi")
|
337 |
+
) or False
|
338 |
+
|
339 |
+
@property
|
340 |
+
def indices_contain_equal_information(self):
|
341 |
+
"""
|
342 |
+
Returns True if indices are either both above or below fermi.
|
343 |
+
|
344 |
+
Examples
|
345 |
+
========
|
346 |
+
|
347 |
+
>>> from sympy import KroneckerDelta, Symbol
|
348 |
+
>>> a = Symbol('a', above_fermi=True)
|
349 |
+
>>> i = Symbol('i', below_fermi=True)
|
350 |
+
>>> p = Symbol('p')
|
351 |
+
>>> q = Symbol('q')
|
352 |
+
>>> KroneckerDelta(p, q).indices_contain_equal_information
|
353 |
+
True
|
354 |
+
>>> KroneckerDelta(p, q+1).indices_contain_equal_information
|
355 |
+
True
|
356 |
+
>>> KroneckerDelta(i, p).indices_contain_equal_information
|
357 |
+
False
|
358 |
+
|
359 |
+
"""
|
360 |
+
if (self.args[0].assumptions0.get("below_fermi") and
|
361 |
+
self.args[1].assumptions0.get("below_fermi")):
|
362 |
+
return True
|
363 |
+
if (self.args[0].assumptions0.get("above_fermi")
|
364 |
+
and self.args[1].assumptions0.get("above_fermi")):
|
365 |
+
return True
|
366 |
+
|
367 |
+
# if both indices are general we are True, else false
|
368 |
+
return self.is_below_fermi and self.is_above_fermi
|
369 |
+
|
370 |
+
@property
|
371 |
+
def preferred_index(self):
|
372 |
+
"""
|
373 |
+
Returns the index which is preferred to keep in the final expression.
|
374 |
+
|
375 |
+
Explanation
|
376 |
+
===========
|
377 |
+
|
378 |
+
The preferred index is the index with more information regarding fermi
|
379 |
+
level. If indices contain the same information, 'a' is preferred before
|
380 |
+
'b'.
|
381 |
+
|
382 |
+
Examples
|
383 |
+
========
|
384 |
+
|
385 |
+
>>> from sympy import KroneckerDelta, Symbol
|
386 |
+
>>> a = Symbol('a', above_fermi=True)
|
387 |
+
>>> i = Symbol('i', below_fermi=True)
|
388 |
+
>>> j = Symbol('j', below_fermi=True)
|
389 |
+
>>> p = Symbol('p')
|
390 |
+
>>> KroneckerDelta(p, i).preferred_index
|
391 |
+
i
|
392 |
+
>>> KroneckerDelta(p, a).preferred_index
|
393 |
+
a
|
394 |
+
>>> KroneckerDelta(i, j).preferred_index
|
395 |
+
i
|
396 |
+
|
397 |
+
See Also
|
398 |
+
========
|
399 |
+
|
400 |
+
killable_index
|
401 |
+
|
402 |
+
"""
|
403 |
+
if self._get_preferred_index():
|
404 |
+
return self.args[1]
|
405 |
+
else:
|
406 |
+
return self.args[0]
|
407 |
+
|
408 |
+
@property
|
409 |
+
def killable_index(self):
|
410 |
+
"""
|
411 |
+
Returns the index which is preferred to substitute in the final
|
412 |
+
expression.
|
413 |
+
|
414 |
+
Explanation
|
415 |
+
===========
|
416 |
+
|
417 |
+
The index to substitute is the index with less information regarding
|
418 |
+
fermi level. If indices contain the same information, 'a' is preferred
|
419 |
+
before 'b'.
|
420 |
+
|
421 |
+
Examples
|
422 |
+
========
|
423 |
+
|
424 |
+
>>> from sympy import KroneckerDelta, Symbol
|
425 |
+
>>> a = Symbol('a', above_fermi=True)
|
426 |
+
>>> i = Symbol('i', below_fermi=True)
|
427 |
+
>>> j = Symbol('j', below_fermi=True)
|
428 |
+
>>> p = Symbol('p')
|
429 |
+
>>> KroneckerDelta(p, i).killable_index
|
430 |
+
p
|
431 |
+
>>> KroneckerDelta(p, a).killable_index
|
432 |
+
p
|
433 |
+
>>> KroneckerDelta(i, j).killable_index
|
434 |
+
j
|
435 |
+
|
436 |
+
See Also
|
437 |
+
========
|
438 |
+
|
439 |
+
preferred_index
|
440 |
+
|
441 |
+
"""
|
442 |
+
if self._get_preferred_index():
|
443 |
+
return self.args[0]
|
444 |
+
else:
|
445 |
+
return self.args[1]
|
446 |
+
|
447 |
+
def _get_preferred_index(self):
|
448 |
+
"""
|
449 |
+
Returns the index which is preferred to keep in the final expression.
|
450 |
+
|
451 |
+
The preferred index is the index with more information regarding fermi
|
452 |
+
level. If indices contain the same information, index 0 is returned.
|
453 |
+
|
454 |
+
"""
|
455 |
+
if not self.is_above_fermi:
|
456 |
+
if self.args[0].assumptions0.get("below_fermi"):
|
457 |
+
return 0
|
458 |
+
else:
|
459 |
+
return 1
|
460 |
+
elif not self.is_below_fermi:
|
461 |
+
if self.args[0].assumptions0.get("above_fermi"):
|
462 |
+
return 0
|
463 |
+
else:
|
464 |
+
return 1
|
465 |
+
else:
|
466 |
+
return 0
|
467 |
+
|
468 |
+
@property
|
469 |
+
def indices(self):
|
470 |
+
return self.args[0:2]
|
471 |
+
|
472 |
+
def _eval_rewrite_as_Piecewise(self, *args, **kwargs):
|
473 |
+
i, j = args
|
474 |
+
return Piecewise((0, Ne(i, j)), (1, True))
|
venv/lib/python3.10/site-packages/sympy/functions/special/tests/__init__.py
ADDED
File without changes
|