diff --git "a/venv/lib/python3.10/site-packages/scipy/special/_basic.py" "b/venv/lib/python3.10/site-packages/scipy/special/_basic.py" new file mode 100644--- /dev/null +++ "b/venv/lib/python3.10/site-packages/scipy/special/_basic.py" @@ -0,0 +1,3398 @@ +# +# Author: Travis Oliphant, 2002 +# + +import operator +import numpy as np +import math +import warnings +from collections import defaultdict +from heapq import heapify, heappop +from numpy import (pi, asarray, floor, isscalar, iscomplex, sqrt, where, mgrid, + sin, place, issubdtype, extract, inexact, nan, zeros, sinc) +from . import _ufuncs +from ._ufuncs import (mathieu_a, mathieu_b, iv, jv, gamma, + psi, hankel1, hankel2, yv, kv, poch, binom, + _stirling2_inexact) +from . import _specfun +from ._comb import _comb_int +from scipy._lib.deprecation import _NoValue, _deprecate_positional_args + + +__all__ = [ + 'ai_zeros', + 'assoc_laguerre', + 'bei_zeros', + 'beip_zeros', + 'ber_zeros', + 'bernoulli', + 'berp_zeros', + 'bi_zeros', + 'clpmn', + 'comb', + 'digamma', + 'diric', + 'erf_zeros', + 'euler', + 'factorial', + 'factorial2', + 'factorialk', + 'fresnel_zeros', + 'fresnelc_zeros', + 'fresnels_zeros', + 'h1vp', + 'h2vp', + 'ivp', + 'jn_zeros', + 'jnjnp_zeros', + 'jnp_zeros', + 'jnyn_zeros', + 'jvp', + 'kei_zeros', + 'keip_zeros', + 'kelvin_zeros', + 'ker_zeros', + 'kerp_zeros', + 'kvp', + 'lmbda', + 'lpmn', + 'lpn', + 'lqmn', + 'lqn', + 'mathieu_even_coef', + 'mathieu_odd_coef', + 'obl_cv_seq', + 'pbdn_seq', + 'pbdv_seq', + 'pbvv_seq', + 'perm', + 'polygamma', + 'pro_cv_seq', + 'riccati_jn', + 'riccati_yn', + 'sinc', + 'stirling2', + 'y0_zeros', + 'y1_zeros', + 'y1p_zeros', + 'yn_zeros', + 'ynp_zeros', + 'yvp', + 'zeta' +] + + +# mapping k to last n such that factorialk(n, k) < np.iinfo(np.int64).max +_FACTORIALK_LIMITS_64BITS = {1: 20, 2: 33, 3: 44, 4: 54, 5: 65, + 6: 74, 7: 84, 8: 93, 9: 101} +# mapping k to last n such that factorialk(n, k) < np.iinfo(np.int32).max +_FACTORIALK_LIMITS_32BITS = {1: 12, 2: 19, 3: 25, 4: 31, 5: 37, + 6: 43, 7: 47, 8: 51, 9: 56} + + +def _nonneg_int_or_fail(n, var_name, strict=True): + try: + if strict: + # Raises an exception if float + n = operator.index(n) + elif n == floor(n): + n = int(n) + else: + raise ValueError() + if n < 0: + raise ValueError() + except (ValueError, TypeError) as err: + raise err.__class__(f"{var_name} must be a non-negative integer") from err + return n + + +def diric(x, n): + """Periodic sinc function, also called the Dirichlet function. + + The Dirichlet function is defined as:: + + diric(x, n) = sin(x * n/2) / (n * sin(x / 2)), + + where `n` is a positive integer. + + Parameters + ---------- + x : array_like + Input data + n : int + Integer defining the periodicity. + + Returns + ------- + diric : ndarray + + Examples + -------- + >>> import numpy as np + >>> from scipy import special + >>> import matplotlib.pyplot as plt + + >>> x = np.linspace(-8*np.pi, 8*np.pi, num=201) + >>> plt.figure(figsize=(8, 8)); + >>> for idx, n in enumerate([2, 3, 4, 9]): + ... plt.subplot(2, 2, idx+1) + ... plt.plot(x, special.diric(x, n)) + ... plt.title('diric, n={}'.format(n)) + >>> plt.show() + + The following example demonstrates that `diric` gives the magnitudes + (modulo the sign and scaling) of the Fourier coefficients of a + rectangular pulse. + + Suppress output of values that are effectively 0: + + >>> np.set_printoptions(suppress=True) + + Create a signal `x` of length `m` with `k` ones: + + >>> m = 8 + >>> k = 3 + >>> x = np.zeros(m) + >>> x[:k] = 1 + + Use the FFT to compute the Fourier transform of `x`, and + inspect the magnitudes of the coefficients: + + >>> np.abs(np.fft.fft(x)) + array([ 3. , 2.41421356, 1. , 0.41421356, 1. , + 0.41421356, 1. , 2.41421356]) + + Now find the same values (up to sign) using `diric`. We multiply + by `k` to account for the different scaling conventions of + `numpy.fft.fft` and `diric`: + + >>> theta = np.linspace(0, 2*np.pi, m, endpoint=False) + >>> k * special.diric(theta, k) + array([ 3. , 2.41421356, 1. , -0.41421356, -1. , + -0.41421356, 1. , 2.41421356]) + """ + x, n = asarray(x), asarray(n) + n = asarray(n + (x-x)) + x = asarray(x + (n-n)) + if issubdtype(x.dtype, inexact): + ytype = x.dtype + else: + ytype = float + y = zeros(x.shape, ytype) + + # empirical minval for 32, 64 or 128 bit float computations + # where sin(x/2) < minval, result is fixed at +1 or -1 + if np.finfo(ytype).eps < 1e-18: + minval = 1e-11 + elif np.finfo(ytype).eps < 1e-15: + minval = 1e-7 + else: + minval = 1e-3 + + mask1 = (n <= 0) | (n != floor(n)) + place(y, mask1, nan) + + x = x / 2 + denom = sin(x) + mask2 = (1-mask1) & (abs(denom) < minval) + xsub = extract(mask2, x) + nsub = extract(mask2, n) + zsub = xsub / pi + place(y, mask2, pow(-1, np.round(zsub)*(nsub-1))) + + mask = (1-mask1) & (1-mask2) + xsub = extract(mask, x) + nsub = extract(mask, n) + dsub = extract(mask, denom) + place(y, mask, sin(nsub*xsub)/(nsub*dsub)) + return y + + +def jnjnp_zeros(nt): + """Compute zeros of integer-order Bessel functions Jn and Jn'. + + Results are arranged in order of the magnitudes of the zeros. + + Parameters + ---------- + nt : int + Number (<=1200) of zeros to compute + + Returns + ------- + zo[l-1] : ndarray + Value of the lth zero of Jn(x) and Jn'(x). Of length `nt`. + n[l-1] : ndarray + Order of the Jn(x) or Jn'(x) associated with lth zero. Of length `nt`. + m[l-1] : ndarray + Serial number of the zeros of Jn(x) or Jn'(x) associated + with lth zero. Of length `nt`. + t[l-1] : ndarray + 0 if lth zero in zo is zero of Jn(x), 1 if it is a zero of Jn'(x). Of + length `nt`. + + See Also + -------- + jn_zeros, jnp_zeros : to get separated arrays of zeros. + + References + ---------- + .. [1] Zhang, Shanjie and Jin, Jianming. "Computation of Special + Functions", John Wiley and Sons, 1996, chapter 5. + https://people.sc.fsu.edu/~jburkardt/f77_src/special_functions/special_functions.html + + """ + if not isscalar(nt) or (floor(nt) != nt) or (nt > 1200): + raise ValueError("Number must be integer <= 1200.") + nt = int(nt) + n, m, t, zo = _specfun.jdzo(nt) + return zo[1:nt+1], n[:nt], m[:nt], t[:nt] + + +def jnyn_zeros(n, nt): + """Compute nt zeros of Bessel functions Jn(x), Jn'(x), Yn(x), and Yn'(x). + + Returns 4 arrays of length `nt`, corresponding to the first `nt` + zeros of Jn(x), Jn'(x), Yn(x), and Yn'(x), respectively. The zeros + are returned in ascending order. + + Parameters + ---------- + n : int + Order of the Bessel functions + nt : int + Number (<=1200) of zeros to compute + + Returns + ------- + Jn : ndarray + First `nt` zeros of Jn + Jnp : ndarray + First `nt` zeros of Jn' + Yn : ndarray + First `nt` zeros of Yn + Ynp : ndarray + First `nt` zeros of Yn' + + See Also + -------- + jn_zeros, jnp_zeros, yn_zeros, ynp_zeros + + References + ---------- + .. [1] Zhang, Shanjie and Jin, Jianming. "Computation of Special + Functions", John Wiley and Sons, 1996, chapter 5. + https://people.sc.fsu.edu/~jburkardt/f77_src/special_functions/special_functions.html + + Examples + -------- + Compute the first three roots of :math:`J_1`, :math:`J_1'`, + :math:`Y_1` and :math:`Y_1'`. + + >>> from scipy.special import jnyn_zeros + >>> jn_roots, jnp_roots, yn_roots, ynp_roots = jnyn_zeros(1, 3) + >>> jn_roots, yn_roots + (array([ 3.83170597, 7.01558667, 10.17346814]), + array([2.19714133, 5.42968104, 8.59600587])) + + Plot :math:`J_1`, :math:`J_1'`, :math:`Y_1`, :math:`Y_1'` and their roots. + + >>> import numpy as np + >>> import matplotlib.pyplot as plt + >>> from scipy.special import jnyn_zeros, jvp, jn, yvp, yn + >>> jn_roots, jnp_roots, yn_roots, ynp_roots = jnyn_zeros(1, 3) + >>> fig, ax = plt.subplots() + >>> xmax= 11 + >>> x = np.linspace(0, xmax) + >>> x[0] += 1e-15 + >>> ax.plot(x, jn(1, x), label=r"$J_1$", c='r') + >>> ax.plot(x, jvp(1, x, 1), label=r"$J_1'$", c='b') + >>> ax.plot(x, yn(1, x), label=r"$Y_1$", c='y') + >>> ax.plot(x, yvp(1, x, 1), label=r"$Y_1'$", c='c') + >>> zeros = np.zeros((3, )) + >>> ax.scatter(jn_roots, zeros, s=30, c='r', zorder=5, + ... label=r"$J_1$ roots") + >>> ax.scatter(jnp_roots, zeros, s=30, c='b', zorder=5, + ... label=r"$J_1'$ roots") + >>> ax.scatter(yn_roots, zeros, s=30, c='y', zorder=5, + ... label=r"$Y_1$ roots") + >>> ax.scatter(ynp_roots, zeros, s=30, c='c', zorder=5, + ... label=r"$Y_1'$ roots") + >>> ax.hlines(0, 0, xmax, color='k') + >>> ax.set_ylim(-0.6, 0.6) + >>> ax.set_xlim(0, xmax) + >>> ax.legend(ncol=2, bbox_to_anchor=(1., 0.75)) + >>> plt.tight_layout() + >>> plt.show() + """ + if not (isscalar(nt) and isscalar(n)): + raise ValueError("Arguments must be scalars.") + if (floor(n) != n) or (floor(nt) != nt): + raise ValueError("Arguments must be integers.") + if (nt <= 0): + raise ValueError("nt > 0") + return _specfun.jyzo(abs(n), nt) + + +def jn_zeros(n, nt): + r"""Compute zeros of integer-order Bessel functions Jn. + + Compute `nt` zeros of the Bessel functions :math:`J_n(x)` on the + interval :math:`(0, \infty)`. The zeros are returned in ascending + order. Note that this interval excludes the zero at :math:`x = 0` + that exists for :math:`n > 0`. + + Parameters + ---------- + n : int + Order of Bessel function + nt : int + Number of zeros to return + + Returns + ------- + ndarray + First `nt` zeros of the Bessel function. + + See Also + -------- + jv: Real-order Bessel functions of the first kind + jnp_zeros: Zeros of :math:`Jn'` + + References + ---------- + .. [1] Zhang, Shanjie and Jin, Jianming. "Computation of Special + Functions", John Wiley and Sons, 1996, chapter 5. + https://people.sc.fsu.edu/~jburkardt/f77_src/special_functions/special_functions.html + + Examples + -------- + Compute the first four positive roots of :math:`J_3`. + + >>> from scipy.special import jn_zeros + >>> jn_zeros(3, 4) + array([ 6.3801619 , 9.76102313, 13.01520072, 16.22346616]) + + Plot :math:`J_3` and its first four positive roots. Note + that the root located at 0 is not returned by `jn_zeros`. + + >>> import numpy as np + >>> import matplotlib.pyplot as plt + >>> from scipy.special import jn, jn_zeros + >>> j3_roots = jn_zeros(3, 4) + >>> xmax = 18 + >>> xmin = -1 + >>> x = np.linspace(xmin, xmax, 500) + >>> fig, ax = plt.subplots() + >>> ax.plot(x, jn(3, x), label=r'$J_3$') + >>> ax.scatter(j3_roots, np.zeros((4, )), s=30, c='r', + ... label=r"$J_3$_Zeros", zorder=5) + >>> ax.scatter(0, 0, s=30, c='k', + ... label=r"Root at 0", zorder=5) + >>> ax.hlines(0, 0, xmax, color='k') + >>> ax.set_xlim(xmin, xmax) + >>> plt.legend() + >>> plt.show() + """ + return jnyn_zeros(n, nt)[0] + + +def jnp_zeros(n, nt): + r"""Compute zeros of integer-order Bessel function derivatives Jn'. + + Compute `nt` zeros of the functions :math:`J_n'(x)` on the + interval :math:`(0, \infty)`. The zeros are returned in ascending + order. Note that this interval excludes the zero at :math:`x = 0` + that exists for :math:`n > 1`. + + Parameters + ---------- + n : int + Order of Bessel function + nt : int + Number of zeros to return + + Returns + ------- + ndarray + First `nt` zeros of the Bessel function. + + See Also + -------- + jvp: Derivatives of integer-order Bessel functions of the first kind + jv: Float-order Bessel functions of the first kind + + References + ---------- + .. [1] Zhang, Shanjie and Jin, Jianming. "Computation of Special + Functions", John Wiley and Sons, 1996, chapter 5. + https://people.sc.fsu.edu/~jburkardt/f77_src/special_functions/special_functions.html + + Examples + -------- + Compute the first four roots of :math:`J_2'`. + + >>> from scipy.special import jnp_zeros + >>> jnp_zeros(2, 4) + array([ 3.05423693, 6.70613319, 9.96946782, 13.17037086]) + + As `jnp_zeros` yields the roots of :math:`J_n'`, it can be used to + compute the locations of the peaks of :math:`J_n`. Plot + :math:`J_2`, :math:`J_2'` and the locations of the roots of :math:`J_2'`. + + >>> import numpy as np + >>> import matplotlib.pyplot as plt + >>> from scipy.special import jn, jnp_zeros, jvp + >>> j2_roots = jnp_zeros(2, 4) + >>> xmax = 15 + >>> x = np.linspace(0, xmax, 500) + >>> fig, ax = plt.subplots() + >>> ax.plot(x, jn(2, x), label=r'$J_2$') + >>> ax.plot(x, jvp(2, x, 1), label=r"$J_2'$") + >>> ax.hlines(0, 0, xmax, color='k') + >>> ax.scatter(j2_roots, np.zeros((4, )), s=30, c='r', + ... label=r"Roots of $J_2'$", zorder=5) + >>> ax.set_ylim(-0.4, 0.8) + >>> ax.set_xlim(0, xmax) + >>> plt.legend() + >>> plt.show() + """ + return jnyn_zeros(n, nt)[1] + + +def yn_zeros(n, nt): + r"""Compute zeros of integer-order Bessel function Yn(x). + + Compute `nt` zeros of the functions :math:`Y_n(x)` on the interval + :math:`(0, \infty)`. The zeros are returned in ascending order. + + Parameters + ---------- + n : int + Order of Bessel function + nt : int + Number of zeros to return + + Returns + ------- + ndarray + First `nt` zeros of the Bessel function. + + See Also + -------- + yn: Bessel function of the second kind for integer order + yv: Bessel function of the second kind for real order + + References + ---------- + .. [1] Zhang, Shanjie and Jin, Jianming. "Computation of Special + Functions", John Wiley and Sons, 1996, chapter 5. + https://people.sc.fsu.edu/~jburkardt/f77_src/special_functions/special_functions.html + + Examples + -------- + Compute the first four roots of :math:`Y_2`. + + >>> from scipy.special import yn_zeros + >>> yn_zeros(2, 4) + array([ 3.38424177, 6.79380751, 10.02347798, 13.20998671]) + + Plot :math:`Y_2` and its first four roots. + + >>> import numpy as np + >>> import matplotlib.pyplot as plt + >>> from scipy.special import yn, yn_zeros + >>> xmin = 2 + >>> xmax = 15 + >>> x = np.linspace(xmin, xmax, 500) + >>> fig, ax = plt.subplots() + >>> ax.hlines(0, xmin, xmax, color='k') + >>> ax.plot(x, yn(2, x), label=r'$Y_2$') + >>> ax.scatter(yn_zeros(2, 4), np.zeros((4, )), s=30, c='r', + ... label='Roots', zorder=5) + >>> ax.set_ylim(-0.4, 0.4) + >>> ax.set_xlim(xmin, xmax) + >>> plt.legend() + >>> plt.show() + """ + return jnyn_zeros(n, nt)[2] + + +def ynp_zeros(n, nt): + r"""Compute zeros of integer-order Bessel function derivatives Yn'(x). + + Compute `nt` zeros of the functions :math:`Y_n'(x)` on the + interval :math:`(0, \infty)`. The zeros are returned in ascending + order. + + Parameters + ---------- + n : int + Order of Bessel function + nt : int + Number of zeros to return + + Returns + ------- + ndarray + First `nt` zeros of the Bessel derivative function. + + + See Also + -------- + yvp + + References + ---------- + .. [1] Zhang, Shanjie and Jin, Jianming. "Computation of Special + Functions", John Wiley and Sons, 1996, chapter 5. + https://people.sc.fsu.edu/~jburkardt/f77_src/special_functions/special_functions.html + + Examples + -------- + Compute the first four roots of the first derivative of the + Bessel function of second kind for order 0 :math:`Y_0'`. + + >>> from scipy.special import ynp_zeros + >>> ynp_zeros(0, 4) + array([ 2.19714133, 5.42968104, 8.59600587, 11.74915483]) + + Plot :math:`Y_0`, :math:`Y_0'` and confirm visually that the roots of + :math:`Y_0'` are located at local extrema of :math:`Y_0`. + + >>> import numpy as np + >>> import matplotlib.pyplot as plt + >>> from scipy.special import yn, ynp_zeros, yvp + >>> zeros = ynp_zeros(0, 4) + >>> xmax = 13 + >>> x = np.linspace(0, xmax, 500) + >>> fig, ax = plt.subplots() + >>> ax.plot(x, yn(0, x), label=r'$Y_0$') + >>> ax.plot(x, yvp(0, x, 1), label=r"$Y_0'$") + >>> ax.scatter(zeros, np.zeros((4, )), s=30, c='r', + ... label=r"Roots of $Y_0'$", zorder=5) + >>> for root in zeros: + ... y0_extremum = yn(0, root) + ... lower = min(0, y0_extremum) + ... upper = max(0, y0_extremum) + ... ax.vlines(root, lower, upper, color='r') + >>> ax.hlines(0, 0, xmax, color='k') + >>> ax.set_ylim(-0.6, 0.6) + >>> ax.set_xlim(0, xmax) + >>> plt.legend() + >>> plt.show() + """ + return jnyn_zeros(n, nt)[3] + + +def y0_zeros(nt, complex=False): + """Compute nt zeros of Bessel function Y0(z), and derivative at each zero. + + The derivatives are given by Y0'(z0) = -Y1(z0) at each zero z0. + + Parameters + ---------- + nt : int + Number of zeros to return + complex : bool, default False + Set to False to return only the real zeros; set to True to return only + the complex zeros with negative real part and positive imaginary part. + Note that the complex conjugates of the latter are also zeros of the + function, but are not returned by this routine. + + Returns + ------- + z0n : ndarray + Location of nth zero of Y0(z) + y0pz0n : ndarray + Value of derivative Y0'(z0) for nth zero + + References + ---------- + .. [1] Zhang, Shanjie and Jin, Jianming. "Computation of Special + Functions", John Wiley and Sons, 1996, chapter 5. + https://people.sc.fsu.edu/~jburkardt/f77_src/special_functions/special_functions.html + + Examples + -------- + Compute the first 4 real roots and the derivatives at the roots of + :math:`Y_0`: + + >>> import numpy as np + >>> from scipy.special import y0_zeros + >>> zeros, grads = y0_zeros(4) + >>> with np.printoptions(precision=5): + ... print(f"Roots: {zeros}") + ... print(f"Gradients: {grads}") + Roots: [ 0.89358+0.j 3.95768+0.j 7.08605+0.j 10.22235+0.j] + Gradients: [-0.87942+0.j 0.40254+0.j -0.3001 +0.j 0.2497 +0.j] + + Plot the real part of :math:`Y_0` and the first four computed roots. + + >>> import matplotlib.pyplot as plt + >>> from scipy.special import y0 + >>> xmin = 0 + >>> xmax = 11 + >>> x = np.linspace(xmin, xmax, 500) + >>> fig, ax = plt.subplots() + >>> ax.hlines(0, xmin, xmax, color='k') + >>> ax.plot(x, y0(x), label=r'$Y_0$') + >>> zeros, grads = y0_zeros(4) + >>> ax.scatter(zeros.real, np.zeros((4, )), s=30, c='r', + ... label=r'$Y_0$_zeros', zorder=5) + >>> ax.set_ylim(-0.5, 0.6) + >>> ax.set_xlim(xmin, xmax) + >>> plt.legend(ncol=2) + >>> plt.show() + + Compute the first 4 complex roots and the derivatives at the roots of + :math:`Y_0` by setting ``complex=True``: + + >>> y0_zeros(4, True) + (array([ -2.40301663+0.53988231j, -5.5198767 +0.54718001j, + -8.6536724 +0.54841207j, -11.79151203+0.54881912j]), + array([ 0.10074769-0.88196771j, -0.02924642+0.5871695j , + 0.01490806-0.46945875j, -0.00937368+0.40230454j])) + """ + if not isscalar(nt) or (floor(nt) != nt) or (nt <= 0): + raise ValueError("Arguments must be scalar positive integer.") + kf = 0 + kc = not complex + return _specfun.cyzo(nt, kf, kc) + + +def y1_zeros(nt, complex=False): + """Compute nt zeros of Bessel function Y1(z), and derivative at each zero. + + The derivatives are given by Y1'(z1) = Y0(z1) at each zero z1. + + Parameters + ---------- + nt : int + Number of zeros to return + complex : bool, default False + Set to False to return only the real zeros; set to True to return only + the complex zeros with negative real part and positive imaginary part. + Note that the complex conjugates of the latter are also zeros of the + function, but are not returned by this routine. + + Returns + ------- + z1n : ndarray + Location of nth zero of Y1(z) + y1pz1n : ndarray + Value of derivative Y1'(z1) for nth zero + + References + ---------- + .. [1] Zhang, Shanjie and Jin, Jianming. "Computation of Special + Functions", John Wiley and Sons, 1996, chapter 5. + https://people.sc.fsu.edu/~jburkardt/f77_src/special_functions/special_functions.html + + Examples + -------- + Compute the first 4 real roots and the derivatives at the roots of + :math:`Y_1`: + + >>> import numpy as np + >>> from scipy.special import y1_zeros + >>> zeros, grads = y1_zeros(4) + >>> with np.printoptions(precision=5): + ... print(f"Roots: {zeros}") + ... print(f"Gradients: {grads}") + Roots: [ 2.19714+0.j 5.42968+0.j 8.59601+0.j 11.74915+0.j] + Gradients: [ 0.52079+0.j -0.34032+0.j 0.27146+0.j -0.23246+0.j] + + Extract the real parts: + + >>> realzeros = zeros.real + >>> realzeros + array([ 2.19714133, 5.42968104, 8.59600587, 11.74915483]) + + Plot :math:`Y_1` and the first four computed roots. + + >>> import matplotlib.pyplot as plt + >>> from scipy.special import y1 + >>> xmin = 0 + >>> xmax = 13 + >>> x = np.linspace(xmin, xmax, 500) + >>> zeros, grads = y1_zeros(4) + >>> fig, ax = plt.subplots() + >>> ax.hlines(0, xmin, xmax, color='k') + >>> ax.plot(x, y1(x), label=r'$Y_1$') + >>> ax.scatter(zeros.real, np.zeros((4, )), s=30, c='r', + ... label=r'$Y_1$_zeros', zorder=5) + >>> ax.set_ylim(-0.5, 0.5) + >>> ax.set_xlim(xmin, xmax) + >>> plt.legend() + >>> plt.show() + + Compute the first 4 complex roots and the derivatives at the roots of + :math:`Y_1` by setting ``complex=True``: + + >>> y1_zeros(4, True) + (array([ -0.50274327+0.78624371j, -3.83353519+0.56235654j, + -7.01590368+0.55339305j, -10.17357383+0.55127339j]), + array([-0.45952768+1.31710194j, 0.04830191-0.69251288j, + -0.02012695+0.51864253j, 0.011614 -0.43203296j])) + """ + if not isscalar(nt) or (floor(nt) != nt) or (nt <= 0): + raise ValueError("Arguments must be scalar positive integer.") + kf = 1 + kc = not complex + return _specfun.cyzo(nt, kf, kc) + + +def y1p_zeros(nt, complex=False): + """Compute nt zeros of Bessel derivative Y1'(z), and value at each zero. + + The values are given by Y1(z1) at each z1 where Y1'(z1)=0. + + Parameters + ---------- + nt : int + Number of zeros to return + complex : bool, default False + Set to False to return only the real zeros; set to True to return only + the complex zeros with negative real part and positive imaginary part. + Note that the complex conjugates of the latter are also zeros of the + function, but are not returned by this routine. + + Returns + ------- + z1pn : ndarray + Location of nth zero of Y1'(z) + y1z1pn : ndarray + Value of derivative Y1(z1) for nth zero + + References + ---------- + .. [1] Zhang, Shanjie and Jin, Jianming. "Computation of Special + Functions", John Wiley and Sons, 1996, chapter 5. + https://people.sc.fsu.edu/~jburkardt/f77_src/special_functions/special_functions.html + + Examples + -------- + Compute the first four roots of :math:`Y_1'` and the values of + :math:`Y_1` at these roots. + + >>> import numpy as np + >>> from scipy.special import y1p_zeros + >>> y1grad_roots, y1_values = y1p_zeros(4) + >>> with np.printoptions(precision=5): + ... print(f"Y1' Roots: {y1grad_roots.real}") + ... print(f"Y1 values: {y1_values.real}") + Y1' Roots: [ 3.68302 6.9415 10.1234 13.28576] + Y1 values: [ 0.41673 -0.30317 0.25091 -0.21897] + + `y1p_zeros` can be used to calculate the extremal points of :math:`Y_1` + directly. Here we plot :math:`Y_1` and the first four extrema. + + >>> import matplotlib.pyplot as plt + >>> from scipy.special import y1, yvp + >>> y1_roots, y1_values_at_roots = y1p_zeros(4) + >>> real_roots = y1_roots.real + >>> xmax = 15 + >>> x = np.linspace(0, xmax, 500) + >>> x[0] += 1e-15 + >>> fig, ax = plt.subplots() + >>> ax.plot(x, y1(x), label=r'$Y_1$') + >>> ax.plot(x, yvp(1, x, 1), label=r"$Y_1'$") + >>> ax.scatter(real_roots, np.zeros((4, )), s=30, c='r', + ... label=r"Roots of $Y_1'$", zorder=5) + >>> ax.scatter(real_roots, y1_values_at_roots.real, s=30, c='k', + ... label=r"Extrema of $Y_1$", zorder=5) + >>> ax.hlines(0, 0, xmax, color='k') + >>> ax.set_ylim(-0.5, 0.5) + >>> ax.set_xlim(0, xmax) + >>> ax.legend(ncol=2, bbox_to_anchor=(1., 0.75)) + >>> plt.tight_layout() + >>> plt.show() + """ + if not isscalar(nt) or (floor(nt) != nt) or (nt <= 0): + raise ValueError("Arguments must be scalar positive integer.") + kf = 2 + kc = not complex + return _specfun.cyzo(nt, kf, kc) + + +def _bessel_diff_formula(v, z, n, L, phase): + # from AMS55. + # L(v, z) = J(v, z), Y(v, z), H1(v, z), H2(v, z), phase = -1 + # L(v, z) = I(v, z) or exp(v*pi*i)K(v, z), phase = 1 + # For K, you can pull out the exp((v-k)*pi*i) into the caller + v = asarray(v) + p = 1.0 + s = L(v-n, z) + for i in range(1, n+1): + p = phase * (p * (n-i+1)) / i # = choose(k, i) + s += p*L(v-n + i*2, z) + return s / (2.**n) + + +def jvp(v, z, n=1): + """Compute derivatives of Bessel functions of the first kind. + + Compute the nth derivative of the Bessel function `Jv` with + respect to `z`. + + Parameters + ---------- + v : array_like or float + Order of Bessel function + z : complex + Argument at which to evaluate the derivative; can be real or + complex. + n : int, default 1 + Order of derivative. For 0 returns the Bessel function `jv` itself. + + Returns + ------- + scalar or ndarray + Values of the derivative of the Bessel function. + + Notes + ----- + The derivative is computed using the relation DLFM 10.6.7 [2]_. + + References + ---------- + .. [1] Zhang, Shanjie and Jin, Jianming. "Computation of Special + Functions", John Wiley and Sons, 1996, chapter 5. + https://people.sc.fsu.edu/~jburkardt/f77_src/special_functions/special_functions.html + + .. [2] NIST Digital Library of Mathematical Functions. + https://dlmf.nist.gov/10.6.E7 + + Examples + -------- + + Compute the Bessel function of the first kind of order 0 and + its first two derivatives at 1. + + >>> from scipy.special import jvp + >>> jvp(0, 1, 0), jvp(0, 1, 1), jvp(0, 1, 2) + (0.7651976865579666, -0.44005058574493355, -0.3251471008130331) + + Compute the first derivative of the Bessel function of the first + kind for several orders at 1 by providing an array for `v`. + + >>> jvp([0, 1, 2], 1, 1) + array([-0.44005059, 0.3251471 , 0.21024362]) + + Compute the first derivative of the Bessel function of the first + kind of order 0 at several points by providing an array for `z`. + + >>> import numpy as np + >>> points = np.array([0., 1.5, 3.]) + >>> jvp(0, points, 1) + array([-0. , -0.55793651, -0.33905896]) + + Plot the Bessel function of the first kind of order 1 and its + first three derivatives. + + >>> import matplotlib.pyplot as plt + >>> x = np.linspace(-10, 10, 1000) + >>> fig, ax = plt.subplots() + >>> ax.plot(x, jvp(1, x, 0), label=r"$J_1$") + >>> ax.plot(x, jvp(1, x, 1), label=r"$J_1'$") + >>> ax.plot(x, jvp(1, x, 2), label=r"$J_1''$") + >>> ax.plot(x, jvp(1, x, 3), label=r"$J_1'''$") + >>> plt.legend() + >>> plt.show() + """ + n = _nonneg_int_or_fail(n, 'n') + if n == 0: + return jv(v, z) + else: + return _bessel_diff_formula(v, z, n, jv, -1) + + +def yvp(v, z, n=1): + """Compute derivatives of Bessel functions of the second kind. + + Compute the nth derivative of the Bessel function `Yv` with + respect to `z`. + + Parameters + ---------- + v : array_like of float + Order of Bessel function + z : complex + Argument at which to evaluate the derivative + n : int, default 1 + Order of derivative. For 0 returns the BEssel function `yv` + + Returns + ------- + scalar or ndarray + nth derivative of the Bessel function. + + See Also + -------- + yv : Bessel functions of the second kind + + Notes + ----- + The derivative is computed using the relation DLFM 10.6.7 [2]_. + + References + ---------- + .. [1] Zhang, Shanjie and Jin, Jianming. "Computation of Special + Functions", John Wiley and Sons, 1996, chapter 5. + https://people.sc.fsu.edu/~jburkardt/f77_src/special_functions/special_functions.html + + .. [2] NIST Digital Library of Mathematical Functions. + https://dlmf.nist.gov/10.6.E7 + + Examples + -------- + Compute the Bessel function of the second kind of order 0 and + its first two derivatives at 1. + + >>> from scipy.special import yvp + >>> yvp(0, 1, 0), yvp(0, 1, 1), yvp(0, 1, 2) + (0.088256964215677, 0.7812128213002889, -0.8694697855159659) + + Compute the first derivative of the Bessel function of the second + kind for several orders at 1 by providing an array for `v`. + + >>> yvp([0, 1, 2], 1, 1) + array([0.78121282, 0.86946979, 2.52015239]) + + Compute the first derivative of the Bessel function of the + second kind of order 0 at several points by providing an array for `z`. + + >>> import numpy as np + >>> points = np.array([0.5, 1.5, 3.]) + >>> yvp(0, points, 1) + array([ 1.47147239, 0.41230863, -0.32467442]) + + Plot the Bessel function of the second kind of order 1 and its + first three derivatives. + + >>> import matplotlib.pyplot as plt + >>> x = np.linspace(0, 5, 1000) + >>> x[0] += 1e-15 + >>> fig, ax = plt.subplots() + >>> ax.plot(x, yvp(1, x, 0), label=r"$Y_1$") + >>> ax.plot(x, yvp(1, x, 1), label=r"$Y_1'$") + >>> ax.plot(x, yvp(1, x, 2), label=r"$Y_1''$") + >>> ax.plot(x, yvp(1, x, 3), label=r"$Y_1'''$") + >>> ax.set_ylim(-10, 10) + >>> plt.legend() + >>> plt.show() + """ + n = _nonneg_int_or_fail(n, 'n') + if n == 0: + return yv(v, z) + else: + return _bessel_diff_formula(v, z, n, yv, -1) + + +def kvp(v, z, n=1): + """Compute derivatives of real-order modified Bessel function Kv(z) + + Kv(z) is the modified Bessel function of the second kind. + Derivative is calculated with respect to `z`. + + Parameters + ---------- + v : array_like of float + Order of Bessel function + z : array_like of complex + Argument at which to evaluate the derivative + n : int, default 1 + Order of derivative. For 0 returns the Bessel function `kv` itself. + + Returns + ------- + out : ndarray + The results + + See Also + -------- + kv + + Notes + ----- + The derivative is computed using the relation DLFM 10.29.5 [2]_. + + References + ---------- + .. [1] Zhang, Shanjie and Jin, Jianming. "Computation of Special + Functions", John Wiley and Sons, 1996, chapter 6. + https://people.sc.fsu.edu/~jburkardt/f77_src/special_functions/special_functions.html + + .. [2] NIST Digital Library of Mathematical Functions. + https://dlmf.nist.gov/10.29.E5 + + Examples + -------- + Compute the modified bessel function of the second kind of order 0 and + its first two derivatives at 1. + + >>> from scipy.special import kvp + >>> kvp(0, 1, 0), kvp(0, 1, 1), kvp(0, 1, 2) + (0.42102443824070834, -0.6019072301972346, 1.0229316684379428) + + Compute the first derivative of the modified Bessel function of the second + kind for several orders at 1 by providing an array for `v`. + + >>> kvp([0, 1, 2], 1, 1) + array([-0.60190723, -1.02293167, -3.85158503]) + + Compute the first derivative of the modified Bessel function of the + second kind of order 0 at several points by providing an array for `z`. + + >>> import numpy as np + >>> points = np.array([0.5, 1.5, 3.]) + >>> kvp(0, points, 1) + array([-1.65644112, -0.2773878 , -0.04015643]) + + Plot the modified bessel function of the second kind and its + first three derivatives. + + >>> import matplotlib.pyplot as plt + >>> x = np.linspace(0, 5, 1000) + >>> fig, ax = plt.subplots() + >>> ax.plot(x, kvp(1, x, 0), label=r"$K_1$") + >>> ax.plot(x, kvp(1, x, 1), label=r"$K_1'$") + >>> ax.plot(x, kvp(1, x, 2), label=r"$K_1''$") + >>> ax.plot(x, kvp(1, x, 3), label=r"$K_1'''$") + >>> ax.set_ylim(-2.5, 2.5) + >>> plt.legend() + >>> plt.show() + """ + n = _nonneg_int_or_fail(n, 'n') + if n == 0: + return kv(v, z) + else: + return (-1)**n * _bessel_diff_formula(v, z, n, kv, 1) + + +def ivp(v, z, n=1): + """Compute derivatives of modified Bessel functions of the first kind. + + Compute the nth derivative of the modified Bessel function `Iv` + with respect to `z`. + + Parameters + ---------- + v : array_like or float + Order of Bessel function + z : array_like + Argument at which to evaluate the derivative; can be real or + complex. + n : int, default 1 + Order of derivative. For 0, returns the Bessel function `iv` itself. + + Returns + ------- + scalar or ndarray + nth derivative of the modified Bessel function. + + See Also + -------- + iv + + Notes + ----- + The derivative is computed using the relation DLFM 10.29.5 [2]_. + + References + ---------- + .. [1] Zhang, Shanjie and Jin, Jianming. "Computation of Special + Functions", John Wiley and Sons, 1996, chapter 6. + https://people.sc.fsu.edu/~jburkardt/f77_src/special_functions/special_functions.html + + .. [2] NIST Digital Library of Mathematical Functions. + https://dlmf.nist.gov/10.29.E5 + + Examples + -------- + Compute the modified Bessel function of the first kind of order 0 and + its first two derivatives at 1. + + >>> from scipy.special import ivp + >>> ivp(0, 1, 0), ivp(0, 1, 1), ivp(0, 1, 2) + (1.2660658777520084, 0.565159103992485, 0.7009067737595233) + + Compute the first derivative of the modified Bessel function of the first + kind for several orders at 1 by providing an array for `v`. + + >>> ivp([0, 1, 2], 1, 1) + array([0.5651591 , 0.70090677, 0.29366376]) + + Compute the first derivative of the modified Bessel function of the + first kind of order 0 at several points by providing an array for `z`. + + >>> import numpy as np + >>> points = np.array([0., 1.5, 3.]) + >>> ivp(0, points, 1) + array([0. , 0.98166643, 3.95337022]) + + Plot the modified Bessel function of the first kind of order 1 and its + first three derivatives. + + >>> import matplotlib.pyplot as plt + >>> x = np.linspace(-5, 5, 1000) + >>> fig, ax = plt.subplots() + >>> ax.plot(x, ivp(1, x, 0), label=r"$I_1$") + >>> ax.plot(x, ivp(1, x, 1), label=r"$I_1'$") + >>> ax.plot(x, ivp(1, x, 2), label=r"$I_1''$") + >>> ax.plot(x, ivp(1, x, 3), label=r"$I_1'''$") + >>> plt.legend() + >>> plt.show() + """ + n = _nonneg_int_or_fail(n, 'n') + if n == 0: + return iv(v, z) + else: + return _bessel_diff_formula(v, z, n, iv, 1) + + +def h1vp(v, z, n=1): + """Compute derivatives of Hankel function H1v(z) with respect to `z`. + + Parameters + ---------- + v : array_like + Order of Hankel function + z : array_like + Argument at which to evaluate the derivative. Can be real or + complex. + n : int, default 1 + Order of derivative. For 0 returns the Hankel function `h1v` itself. + + Returns + ------- + scalar or ndarray + Values of the derivative of the Hankel function. + + See Also + -------- + hankel1 + + Notes + ----- + The derivative is computed using the relation DLFM 10.6.7 [2]_. + + References + ---------- + .. [1] Zhang, Shanjie and Jin, Jianming. "Computation of Special + Functions", John Wiley and Sons, 1996, chapter 5. + https://people.sc.fsu.edu/~jburkardt/f77_src/special_functions/special_functions.html + + .. [2] NIST Digital Library of Mathematical Functions. + https://dlmf.nist.gov/10.6.E7 + + Examples + -------- + Compute the Hankel function of the first kind of order 0 and + its first two derivatives at 1. + + >>> from scipy.special import h1vp + >>> h1vp(0, 1, 0), h1vp(0, 1, 1), h1vp(0, 1, 2) + ((0.7651976865579664+0.088256964215677j), + (-0.44005058574493355+0.7812128213002889j), + (-0.3251471008130329-0.8694697855159659j)) + + Compute the first derivative of the Hankel function of the first kind + for several orders at 1 by providing an array for `v`. + + >>> h1vp([0, 1, 2], 1, 1) + array([-0.44005059+0.78121282j, 0.3251471 +0.86946979j, + 0.21024362+2.52015239j]) + + Compute the first derivative of the Hankel function of the first kind + of order 0 at several points by providing an array for `z`. + + >>> import numpy as np + >>> points = np.array([0.5, 1.5, 3.]) + >>> h1vp(0, points, 1) + array([-0.24226846+1.47147239j, -0.55793651+0.41230863j, + -0.33905896-0.32467442j]) + """ + n = _nonneg_int_or_fail(n, 'n') + if n == 0: + return hankel1(v, z) + else: + return _bessel_diff_formula(v, z, n, hankel1, -1) + + +def h2vp(v, z, n=1): + """Compute derivatives of Hankel function H2v(z) with respect to `z`. + + Parameters + ---------- + v : array_like + Order of Hankel function + z : array_like + Argument at which to evaluate the derivative. Can be real or + complex. + n : int, default 1 + Order of derivative. For 0 returns the Hankel function `h2v` itself. + + Returns + ------- + scalar or ndarray + Values of the derivative of the Hankel function. + + See Also + -------- + hankel2 + + Notes + ----- + The derivative is computed using the relation DLFM 10.6.7 [2]_. + + References + ---------- + .. [1] Zhang, Shanjie and Jin, Jianming. "Computation of Special + Functions", John Wiley and Sons, 1996, chapter 5. + https://people.sc.fsu.edu/~jburkardt/f77_src/special_functions/special_functions.html + + .. [2] NIST Digital Library of Mathematical Functions. + https://dlmf.nist.gov/10.6.E7 + + Examples + -------- + Compute the Hankel function of the second kind of order 0 and + its first two derivatives at 1. + + >>> from scipy.special import h2vp + >>> h2vp(0, 1, 0), h2vp(0, 1, 1), h2vp(0, 1, 2) + ((0.7651976865579664-0.088256964215677j), + (-0.44005058574493355-0.7812128213002889j), + (-0.3251471008130329+0.8694697855159659j)) + + Compute the first derivative of the Hankel function of the second kind + for several orders at 1 by providing an array for `v`. + + >>> h2vp([0, 1, 2], 1, 1) + array([-0.44005059-0.78121282j, 0.3251471 -0.86946979j, + 0.21024362-2.52015239j]) + + Compute the first derivative of the Hankel function of the second kind + of order 0 at several points by providing an array for `z`. + + >>> import numpy as np + >>> points = np.array([0.5, 1.5, 3.]) + >>> h2vp(0, points, 1) + array([-0.24226846-1.47147239j, -0.55793651-0.41230863j, + -0.33905896+0.32467442j]) + """ + n = _nonneg_int_or_fail(n, 'n') + if n == 0: + return hankel2(v, z) + else: + return _bessel_diff_formula(v, z, n, hankel2, -1) + + +def riccati_jn(n, x): + r"""Compute Ricatti-Bessel function of the first kind and its derivative. + + The Ricatti-Bessel function of the first kind is defined as :math:`x + j_n(x)`, where :math:`j_n` is the spherical Bessel function of the first + kind of order :math:`n`. + + This function computes the value and first derivative of the + Ricatti-Bessel function for all orders up to and including `n`. + + Parameters + ---------- + n : int + Maximum order of function to compute + x : float + Argument at which to evaluate + + Returns + ------- + jn : ndarray + Value of j0(x), ..., jn(x) + jnp : ndarray + First derivative j0'(x), ..., jn'(x) + + Notes + ----- + The computation is carried out via backward recurrence, using the + relation DLMF 10.51.1 [2]_. + + Wrapper for a Fortran routine created by Shanjie Zhang and Jianming + Jin [1]_. + + References + ---------- + .. [1] Zhang, Shanjie and Jin, Jianming. "Computation of Special + Functions", John Wiley and Sons, 1996. + https://people.sc.fsu.edu/~jburkardt/f77_src/special_functions/special_functions.html + .. [2] NIST Digital Library of Mathematical Functions. + https://dlmf.nist.gov/10.51.E1 + + """ + if not (isscalar(n) and isscalar(x)): + raise ValueError("arguments must be scalars.") + n = _nonneg_int_or_fail(n, 'n', strict=False) + if (n == 0): + n1 = 1 + else: + n1 = n + nm, jn, jnp = _specfun.rctj(n1, x) + return jn[:(n+1)], jnp[:(n+1)] + + +def riccati_yn(n, x): + """Compute Ricatti-Bessel function of the second kind and its derivative. + + The Ricatti-Bessel function of the second kind is defined as :math:`x + y_n(x)`, where :math:`y_n` is the spherical Bessel function of the second + kind of order :math:`n`. + + This function computes the value and first derivative of the function for + all orders up to and including `n`. + + Parameters + ---------- + n : int + Maximum order of function to compute + x : float + Argument at which to evaluate + + Returns + ------- + yn : ndarray + Value of y0(x), ..., yn(x) + ynp : ndarray + First derivative y0'(x), ..., yn'(x) + + Notes + ----- + The computation is carried out via ascending recurrence, using the + relation DLMF 10.51.1 [2]_. + + Wrapper for a Fortran routine created by Shanjie Zhang and Jianming + Jin [1]_. + + References + ---------- + .. [1] Zhang, Shanjie and Jin, Jianming. "Computation of Special + Functions", John Wiley and Sons, 1996. + https://people.sc.fsu.edu/~jburkardt/f77_src/special_functions/special_functions.html + .. [2] NIST Digital Library of Mathematical Functions. + https://dlmf.nist.gov/10.51.E1 + + """ + if not (isscalar(n) and isscalar(x)): + raise ValueError("arguments must be scalars.") + n = _nonneg_int_or_fail(n, 'n', strict=False) + if (n == 0): + n1 = 1 + else: + n1 = n + nm, jn, jnp = _specfun.rcty(n1, x) + return jn[:(n+1)], jnp[:(n+1)] + + +def erf_zeros(nt): + """Compute the first nt zero in the first quadrant, ordered by absolute value. + + Zeros in the other quadrants can be obtained by using the symmetries + erf(-z) = erf(z) and erf(conj(z)) = conj(erf(z)). + + + Parameters + ---------- + nt : int + The number of zeros to compute + + Returns + ------- + The locations of the zeros of erf : ndarray (complex) + Complex values at which zeros of erf(z) + + References + ---------- + .. [1] Zhang, Shanjie and Jin, Jianming. "Computation of Special + Functions", John Wiley and Sons, 1996. + https://people.sc.fsu.edu/~jburkardt/f77_src/special_functions/special_functions.html + + Examples + -------- + >>> from scipy import special + >>> special.erf_zeros(1) + array([1.45061616+1.880943j]) + + Check that erf is (close to) zero for the value returned by erf_zeros + + >>> special.erf(special.erf_zeros(1)) + array([4.95159469e-14-1.16407394e-16j]) + + """ + if (floor(nt) != nt) or (nt <= 0) or not isscalar(nt): + raise ValueError("Argument must be positive scalar integer.") + return _specfun.cerzo(nt) + + +def fresnelc_zeros(nt): + """Compute nt complex zeros of cosine Fresnel integral C(z). + + Parameters + ---------- + nt : int + Number of zeros to compute + + Returns + ------- + fresnelc_zeros: ndarray + Zeros of the cosine Fresnel integral + + References + ---------- + .. [1] Zhang, Shanjie and Jin, Jianming. "Computation of Special + Functions", John Wiley and Sons, 1996. + https://people.sc.fsu.edu/~jburkardt/f77_src/special_functions/special_functions.html + + """ + if (floor(nt) != nt) or (nt <= 0) or not isscalar(nt): + raise ValueError("Argument must be positive scalar integer.") + return _specfun.fcszo(1, nt) + + +def fresnels_zeros(nt): + """Compute nt complex zeros of sine Fresnel integral S(z). + + Parameters + ---------- + nt : int + Number of zeros to compute + + Returns + ------- + fresnels_zeros: ndarray + Zeros of the sine Fresnel integral + + References + ---------- + .. [1] Zhang, Shanjie and Jin, Jianming. "Computation of Special + Functions", John Wiley and Sons, 1996. + https://people.sc.fsu.edu/~jburkardt/f77_src/special_functions/special_functions.html + + """ + if (floor(nt) != nt) or (nt <= 0) or not isscalar(nt): + raise ValueError("Argument must be positive scalar integer.") + return _specfun.fcszo(2, nt) + + +def fresnel_zeros(nt): + """Compute nt complex zeros of sine and cosine Fresnel integrals S(z) and C(z). + + Parameters + ---------- + nt : int + Number of zeros to compute + + Returns + ------- + zeros_sine: ndarray + Zeros of the sine Fresnel integral + zeros_cosine : ndarray + Zeros of the cosine Fresnel integral + + References + ---------- + .. [1] Zhang, Shanjie and Jin, Jianming. "Computation of Special + Functions", John Wiley and Sons, 1996. + https://people.sc.fsu.edu/~jburkardt/f77_src/special_functions/special_functions.html + + """ + if (floor(nt) != nt) or (nt <= 0) or not isscalar(nt): + raise ValueError("Argument must be positive scalar integer.") + return _specfun.fcszo(2, nt), _specfun.fcszo(1, nt) + + +def assoc_laguerre(x, n, k=0.0): + """Compute the generalized (associated) Laguerre polynomial of degree n and order k. + + The polynomial :math:`L^{(k)}_n(x)` is orthogonal over ``[0, inf)``, + with weighting function ``exp(-x) * x**k`` with ``k > -1``. + + Parameters + ---------- + x : float or ndarray + Points where to evaluate the Laguerre polynomial + n : int + Degree of the Laguerre polynomial + k : int + Order of the Laguerre polynomial + + Returns + ------- + assoc_laguerre: float or ndarray + Associated laguerre polynomial values + + Notes + ----- + `assoc_laguerre` is a simple wrapper around `eval_genlaguerre`, with + reversed argument order ``(x, n, k=0.0) --> (n, k, x)``. + + """ + return _ufuncs.eval_genlaguerre(n, k, x) + + +digamma = psi + + +def polygamma(n, x): + r"""Polygamma functions. + + Defined as :math:`\psi^{(n)}(x)` where :math:`\psi` is the + `digamma` function. See [dlmf]_ for details. + + Parameters + ---------- + n : array_like + The order of the derivative of the digamma function; must be + integral + x : array_like + Real valued input + + Returns + ------- + ndarray + Function results + + See Also + -------- + digamma + + References + ---------- + .. [dlmf] NIST, Digital Library of Mathematical Functions, + https://dlmf.nist.gov/5.15 + + Examples + -------- + >>> from scipy import special + >>> x = [2, 3, 25.5] + >>> special.polygamma(1, x) + array([ 0.64493407, 0.39493407, 0.03999467]) + >>> special.polygamma(0, x) == special.psi(x) + array([ True, True, True], dtype=bool) + + """ + n, x = asarray(n), asarray(x) + fac2 = (-1.0)**(n+1) * gamma(n+1.0) * zeta(n+1, x) + return where(n == 0, psi(x), fac2) + + +def mathieu_even_coef(m, q): + r"""Fourier coefficients for even Mathieu and modified Mathieu functions. + + The Fourier series of the even solutions of the Mathieu differential + equation are of the form + + .. math:: \mathrm{ce}_{2n}(z, q) = \sum_{k=0}^{\infty} A_{(2n)}^{(2k)} \cos 2kz + + .. math:: \mathrm{ce}_{2n+1}(z, q) = + \sum_{k=0}^{\infty} A_{(2n+1)}^{(2k+1)} \cos (2k+1)z + + This function returns the coefficients :math:`A_{(2n)}^{(2k)}` for even + input m=2n, and the coefficients :math:`A_{(2n+1)}^{(2k+1)}` for odd input + m=2n+1. + + Parameters + ---------- + m : int + Order of Mathieu functions. Must be non-negative. + q : float (>=0) + Parameter of Mathieu functions. Must be non-negative. + + Returns + ------- + Ak : ndarray + Even or odd Fourier coefficients, corresponding to even or odd m. + + References + ---------- + .. [1] Zhang, Shanjie and Jin, Jianming. "Computation of Special + Functions", John Wiley and Sons, 1996. + https://people.sc.fsu.edu/~jburkardt/f77_src/special_functions/special_functions.html + .. [2] NIST Digital Library of Mathematical Functions + https://dlmf.nist.gov/28.4#i + + """ + if not (isscalar(m) and isscalar(q)): + raise ValueError("m and q must be scalars.") + if (q < 0): + raise ValueError("q >=0") + if (m != floor(m)) or (m < 0): + raise ValueError("m must be an integer >=0.") + + if (q <= 1): + qm = 7.5 + 56.1*sqrt(q) - 134.7*q + 90.7*sqrt(q)*q + else: + qm = 17.0 + 3.1*sqrt(q) - .126*q + .0037*sqrt(q)*q + km = int(qm + 0.5*m) + if km > 251: + warnings.warn("Too many predicted coefficients.", RuntimeWarning, stacklevel=2) + kd = 1 + m = int(floor(m)) + if m % 2: + kd = 2 + + a = mathieu_a(m, q) + fc = _specfun.fcoef(kd, m, q, a) + return fc[:km] + + +def mathieu_odd_coef(m, q): + r"""Fourier coefficients for even Mathieu and modified Mathieu functions. + + The Fourier series of the odd solutions of the Mathieu differential + equation are of the form + + .. math:: \mathrm{se}_{2n+1}(z, q) = + \sum_{k=0}^{\infty} B_{(2n+1)}^{(2k+1)} \sin (2k+1)z + + .. math:: \mathrm{se}_{2n+2}(z, q) = + \sum_{k=0}^{\infty} B_{(2n+2)}^{(2k+2)} \sin (2k+2)z + + This function returns the coefficients :math:`B_{(2n+2)}^{(2k+2)}` for even + input m=2n+2, and the coefficients :math:`B_{(2n+1)}^{(2k+1)}` for odd + input m=2n+1. + + Parameters + ---------- + m : int + Order of Mathieu functions. Must be non-negative. + q : float (>=0) + Parameter of Mathieu functions. Must be non-negative. + + Returns + ------- + Bk : ndarray + Even or odd Fourier coefficients, corresponding to even or odd m. + + References + ---------- + .. [1] Zhang, Shanjie and Jin, Jianming. "Computation of Special + Functions", John Wiley and Sons, 1996. + https://people.sc.fsu.edu/~jburkardt/f77_src/special_functions/special_functions.html + + """ + if not (isscalar(m) and isscalar(q)): + raise ValueError("m and q must be scalars.") + if (q < 0): + raise ValueError("q >=0") + if (m != floor(m)) or (m <= 0): + raise ValueError("m must be an integer > 0") + + if (q <= 1): + qm = 7.5 + 56.1*sqrt(q) - 134.7*q + 90.7*sqrt(q)*q + else: + qm = 17.0 + 3.1*sqrt(q) - .126*q + .0037*sqrt(q)*q + km = int(qm + 0.5*m) + if km > 251: + warnings.warn("Too many predicted coefficients.", RuntimeWarning, stacklevel=2) + kd = 4 + m = int(floor(m)) + if m % 2: + kd = 3 + + b = mathieu_b(m, q) + fc = _specfun.fcoef(kd, m, q, b) + return fc[:km] + + +def lpmn(m, n, z): + """Sequence of associated Legendre functions of the first kind. + + Computes the associated Legendre function of the first kind of order m and + degree n, ``Pmn(z)`` = :math:`P_n^m(z)`, and its derivative, ``Pmn'(z)``. + Returns two arrays of size ``(m+1, n+1)`` containing ``Pmn(z)`` and + ``Pmn'(z)`` for all orders from ``0..m`` and degrees from ``0..n``. + + This function takes a real argument ``z``. For complex arguments ``z`` + use clpmn instead. + + Parameters + ---------- + m : int + ``|m| <= n``; the order of the Legendre function. + n : int + where ``n >= 0``; the degree of the Legendre function. Often + called ``l`` (lower case L) in descriptions of the associated + Legendre function + z : float + Input value. + + Returns + ------- + Pmn_z : (m+1, n+1) array + Values for all orders 0..m and degrees 0..n + Pmn_d_z : (m+1, n+1) array + Derivatives for all orders 0..m and degrees 0..n + + See Also + -------- + clpmn: associated Legendre functions of the first kind for complex z + + Notes + ----- + In the interval (-1, 1), Ferrer's function of the first kind is + returned. The phase convention used for the intervals (1, inf) + and (-inf, -1) is such that the result is always real. + + References + ---------- + .. [1] Zhang, Shanjie and Jin, Jianming. "Computation of Special + Functions", John Wiley and Sons, 1996. + https://people.sc.fsu.edu/~jburkardt/f77_src/special_functions/special_functions.html + .. [2] NIST Digital Library of Mathematical Functions + https://dlmf.nist.gov/14.3 + + """ + if not isscalar(m) or (abs(m) > n): + raise ValueError("m must be <= n.") + if not isscalar(n) or (n < 0): + raise ValueError("n must be a non-negative integer.") + if not isscalar(z): + raise ValueError("z must be scalar.") + if iscomplex(z): + raise ValueError("Argument must be real. Use clpmn instead.") + if (m < 0): + mp = -m + mf, nf = mgrid[0:mp+1, 0:n+1] + with _ufuncs.errstate(all='ignore'): + if abs(z) < 1: + # Ferrer function; DLMF 14.9.3 + fixarr = where(mf > nf, 0.0, + (-1)**mf * gamma(nf-mf+1) / gamma(nf+mf+1)) + else: + # Match to clpmn; DLMF 14.9.13 + fixarr = where(mf > nf, 0.0, gamma(nf-mf+1) / gamma(nf+mf+1)) + else: + mp = m + p, pd = _specfun.lpmn(mp, n, z) + if (m < 0): + p = p * fixarr + pd = pd * fixarr + return p, pd + + +def clpmn(m, n, z, type=3): + """Associated Legendre function of the first kind for complex arguments. + + Computes the associated Legendre function of the first kind of order m and + degree n, ``Pmn(z)`` = :math:`P_n^m(z)`, and its derivative, ``Pmn'(z)``. + Returns two arrays of size ``(m+1, n+1)`` containing ``Pmn(z)`` and + ``Pmn'(z)`` for all orders from ``0..m`` and degrees from ``0..n``. + + Parameters + ---------- + m : int + ``|m| <= n``; the order of the Legendre function. + n : int + where ``n >= 0``; the degree of the Legendre function. Often + called ``l`` (lower case L) in descriptions of the associated + Legendre function + z : float or complex + Input value. + type : int, optional + takes values 2 or 3 + 2: cut on the real axis ``|x| > 1`` + 3: cut on the real axis ``-1 < x < 1`` (default) + + Returns + ------- + Pmn_z : (m+1, n+1) array + Values for all orders ``0..m`` and degrees ``0..n`` + Pmn_d_z : (m+1, n+1) array + Derivatives for all orders ``0..m`` and degrees ``0..n`` + + See Also + -------- + lpmn: associated Legendre functions of the first kind for real z + + Notes + ----- + By default, i.e. for ``type=3``, phase conventions are chosen according + to [1]_ such that the function is analytic. The cut lies on the interval + (-1, 1). Approaching the cut from above or below in general yields a phase + factor with respect to Ferrer's function of the first kind + (cf. `lpmn`). + + For ``type=2`` a cut at ``|x| > 1`` is chosen. Approaching the real values + on the interval (-1, 1) in the complex plane yields Ferrer's function + of the first kind. + + References + ---------- + .. [1] Zhang, Shanjie and Jin, Jianming. "Computation of Special + Functions", John Wiley and Sons, 1996. + https://people.sc.fsu.edu/~jburkardt/f77_src/special_functions/special_functions.html + .. [2] NIST Digital Library of Mathematical Functions + https://dlmf.nist.gov/14.21 + + """ + if not isscalar(m) or (abs(m) > n): + raise ValueError("m must be <= n.") + if not isscalar(n) or (n < 0): + raise ValueError("n must be a non-negative integer.") + if not isscalar(z): + raise ValueError("z must be scalar.") + if not (type == 2 or type == 3): + raise ValueError("type must be either 2 or 3.") + if (m < 0): + mp = -m + mf, nf = mgrid[0:mp+1, 0:n+1] + with _ufuncs.errstate(all='ignore'): + if type == 2: + fixarr = where(mf > nf, 0.0, + (-1)**mf * gamma(nf-mf+1) / gamma(nf+mf+1)) + else: + fixarr = where(mf > nf, 0.0, gamma(nf-mf+1) / gamma(nf+mf+1)) + else: + mp = m + p, pd = _specfun.clpmn(mp, n, z, type) + if (m < 0): + p = p * fixarr + pd = pd * fixarr + return p, pd + + +def lqmn(m, n, z): + """Sequence of associated Legendre functions of the second kind. + + Computes the associated Legendre function of the second kind of order m and + degree n, ``Qmn(z)`` = :math:`Q_n^m(z)`, and its derivative, ``Qmn'(z)``. + Returns two arrays of size ``(m+1, n+1)`` containing ``Qmn(z)`` and + ``Qmn'(z)`` for all orders from ``0..m`` and degrees from ``0..n``. + + Parameters + ---------- + m : int + ``|m| <= n``; the order of the Legendre function. + n : int + where ``n >= 0``; the degree of the Legendre function. Often + called ``l`` (lower case L) in descriptions of the associated + Legendre function + z : complex + Input value. + + Returns + ------- + Qmn_z : (m+1, n+1) array + Values for all orders 0..m and degrees 0..n + Qmn_d_z : (m+1, n+1) array + Derivatives for all orders 0..m and degrees 0..n + + References + ---------- + .. [1] Zhang, Shanjie and Jin, Jianming. "Computation of Special + Functions", John Wiley and Sons, 1996. + https://people.sc.fsu.edu/~jburkardt/f77_src/special_functions/special_functions.html + + """ + if not isscalar(m) or (m < 0): + raise ValueError("m must be a non-negative integer.") + if not isscalar(n) or (n < 0): + raise ValueError("n must be a non-negative integer.") + if not isscalar(z): + raise ValueError("z must be scalar.") + m = int(m) + n = int(n) + + # Ensure neither m nor n == 0 + mm = max(1, m) + nn = max(1, n) + + if iscomplex(z): + q, qd = _specfun.clqmn(mm, nn, z) + else: + q, qd = _specfun.lqmn(mm, nn, z) + return q[:(m+1), :(n+1)], qd[:(m+1), :(n+1)] + + +def bernoulli(n): + """Bernoulli numbers B0..Bn (inclusive). + + Parameters + ---------- + n : int + Indicated the number of terms in the Bernoulli series to generate. + + Returns + ------- + ndarray + The Bernoulli numbers ``[B(0), B(1), ..., B(n)]``. + + References + ---------- + .. [1] Zhang, Shanjie and Jin, Jianming. "Computation of Special + Functions", John Wiley and Sons, 1996. + https://people.sc.fsu.edu/~jburkardt/f77_src/special_functions/special_functions.html + .. [2] "Bernoulli number", Wikipedia, https://en.wikipedia.org/wiki/Bernoulli_number + + Examples + -------- + >>> import numpy as np + >>> from scipy.special import bernoulli, zeta + >>> bernoulli(4) + array([ 1. , -0.5 , 0.16666667, 0. , -0.03333333]) + + The Wikipedia article ([2]_) points out the relationship between the + Bernoulli numbers and the zeta function, ``B_n^+ = -n * zeta(1 - n)`` + for ``n > 0``: + + >>> n = np.arange(1, 5) + >>> -n * zeta(1 - n) + array([ 0.5 , 0.16666667, -0. , -0.03333333]) + + Note that, in the notation used in the wikipedia article, + `bernoulli` computes ``B_n^-`` (i.e. it used the convention that + ``B_1`` is -1/2). The relation given above is for ``B_n^+``, so the + sign of 0.5 does not match the output of ``bernoulli(4)``. + + """ + if not isscalar(n) or (n < 0): + raise ValueError("n must be a non-negative integer.") + n = int(n) + if (n < 2): + n1 = 2 + else: + n1 = n + return _specfun.bernob(int(n1))[:(n+1)] + + +def euler(n): + """Euler numbers E(0), E(1), ..., E(n). + + The Euler numbers [1]_ are also known as the secant numbers. + + Because ``euler(n)`` returns floating point values, it does not give + exact values for large `n`. The first inexact value is E(22). + + Parameters + ---------- + n : int + The highest index of the Euler number to be returned. + + Returns + ------- + ndarray + The Euler numbers [E(0), E(1), ..., E(n)]. + The odd Euler numbers, which are all zero, are included. + + References + ---------- + .. [1] Sequence A122045, The On-Line Encyclopedia of Integer Sequences, + https://oeis.org/A122045 + .. [2] Zhang, Shanjie and Jin, Jianming. "Computation of Special + Functions", John Wiley and Sons, 1996. + https://people.sc.fsu.edu/~jburkardt/f77_src/special_functions/special_functions.html + + Examples + -------- + >>> import numpy as np + >>> from scipy.special import euler + >>> euler(6) + array([ 1., 0., -1., 0., 5., 0., -61.]) + + >>> euler(13).astype(np.int64) + array([ 1, 0, -1, 0, 5, 0, -61, + 0, 1385, 0, -50521, 0, 2702765, 0]) + + >>> euler(22)[-1] # Exact value of E(22) is -69348874393137901. + -69348874393137976.0 + + """ + if not isscalar(n) or (n < 0): + raise ValueError("n must be a non-negative integer.") + n = int(n) + if (n < 2): + n1 = 2 + else: + n1 = n + return _specfun.eulerb(n1)[:(n+1)] + + +def lpn(n, z): + """Legendre function of the first kind. + + Compute sequence of Legendre functions of the first kind (polynomials), + Pn(z) and derivatives for all degrees from 0 to n (inclusive). + + See also special.legendre for polynomial class. + + References + ---------- + .. [1] Zhang, Shanjie and Jin, Jianming. "Computation of Special + Functions", John Wiley and Sons, 1996. + https://people.sc.fsu.edu/~jburkardt/f77_src/special_functions/special_functions.html + + """ + if not (isscalar(n) and isscalar(z)): + raise ValueError("arguments must be scalars.") + n = _nonneg_int_or_fail(n, 'n', strict=False) + if (n < 1): + n1 = 1 + else: + n1 = n + if iscomplex(z): + pn, pd = _specfun.clpn(n1, z) + else: + pn, pd = _specfun.lpn(n1, z) + return pn[:(n+1)], pd[:(n+1)] + + +def lqn(n, z): + """Legendre function of the second kind. + + Compute sequence of Legendre functions of the second kind, Qn(z) and + derivatives for all degrees from 0 to n (inclusive). + + References + ---------- + .. [1] Zhang, Shanjie and Jin, Jianming. "Computation of Special + Functions", John Wiley and Sons, 1996. + https://people.sc.fsu.edu/~jburkardt/f77_src/special_functions/special_functions.html + + """ + if not (isscalar(n) and isscalar(z)): + raise ValueError("arguments must be scalars.") + n = _nonneg_int_or_fail(n, 'n', strict=False) + if (n < 1): + n1 = 1 + else: + n1 = n + if iscomplex(z): + qn, qd = _specfun.clqn(n1, z) + else: + qn, qd = _specfun.lqnb(n1, z) + return qn[:(n+1)], qd[:(n+1)] + + +def ai_zeros(nt): + """ + Compute `nt` zeros and values of the Airy function Ai and its derivative. + + Computes the first `nt` zeros, `a`, of the Airy function Ai(x); + first `nt` zeros, `ap`, of the derivative of the Airy function Ai'(x); + the corresponding values Ai(a'); + and the corresponding values Ai'(a). + + Parameters + ---------- + nt : int + Number of zeros to compute + + Returns + ------- + a : ndarray + First `nt` zeros of Ai(x) + ap : ndarray + First `nt` zeros of Ai'(x) + ai : ndarray + Values of Ai(x) evaluated at first `nt` zeros of Ai'(x) + aip : ndarray + Values of Ai'(x) evaluated at first `nt` zeros of Ai(x) + + References + ---------- + .. [1] Zhang, Shanjie and Jin, Jianming. "Computation of Special + Functions", John Wiley and Sons, 1996. + https://people.sc.fsu.edu/~jburkardt/f77_src/special_functions/special_functions.html + + Examples + -------- + >>> from scipy import special + >>> a, ap, ai, aip = special.ai_zeros(3) + >>> a + array([-2.33810741, -4.08794944, -5.52055983]) + >>> ap + array([-1.01879297, -3.24819758, -4.82009921]) + >>> ai + array([ 0.53565666, -0.41901548, 0.38040647]) + >>> aip + array([ 0.70121082, -0.80311137, 0.86520403]) + + """ + kf = 1 + if not isscalar(nt) or (floor(nt) != nt) or (nt <= 0): + raise ValueError("nt must be a positive integer scalar.") + return _specfun.airyzo(nt, kf) + + +def bi_zeros(nt): + """ + Compute `nt` zeros and values of the Airy function Bi and its derivative. + + Computes the first `nt` zeros, b, of the Airy function Bi(x); + first `nt` zeros, b', of the derivative of the Airy function Bi'(x); + the corresponding values Bi(b'); + and the corresponding values Bi'(b). + + Parameters + ---------- + nt : int + Number of zeros to compute + + Returns + ------- + b : ndarray + First `nt` zeros of Bi(x) + bp : ndarray + First `nt` zeros of Bi'(x) + bi : ndarray + Values of Bi(x) evaluated at first `nt` zeros of Bi'(x) + bip : ndarray + Values of Bi'(x) evaluated at first `nt` zeros of Bi(x) + + References + ---------- + .. [1] Zhang, Shanjie and Jin, Jianming. "Computation of Special + Functions", John Wiley and Sons, 1996. + https://people.sc.fsu.edu/~jburkardt/f77_src/special_functions/special_functions.html + + Examples + -------- + >>> from scipy import special + >>> b, bp, bi, bip = special.bi_zeros(3) + >>> b + array([-1.17371322, -3.2710933 , -4.83073784]) + >>> bp + array([-2.29443968, -4.07315509, -5.51239573]) + >>> bi + array([-0.45494438, 0.39652284, -0.36796916]) + >>> bip + array([ 0.60195789, -0.76031014, 0.83699101]) + + """ + kf = 2 + if not isscalar(nt) or (floor(nt) != nt) or (nt <= 0): + raise ValueError("nt must be a positive integer scalar.") + return _specfun.airyzo(nt, kf) + + +def lmbda(v, x): + r"""Jahnke-Emden Lambda function, Lambdav(x). + + This function is defined as [2]_, + + .. math:: \Lambda_v(x) = \Gamma(v+1) \frac{J_v(x)}{(x/2)^v}, + + where :math:`\Gamma` is the gamma function and :math:`J_v` is the + Bessel function of the first kind. + + Parameters + ---------- + v : float + Order of the Lambda function + x : float + Value at which to evaluate the function and derivatives + + Returns + ------- + vl : ndarray + Values of Lambda_vi(x), for vi=v-int(v), vi=1+v-int(v), ..., vi=v. + dl : ndarray + Derivatives Lambda_vi'(x), for vi=v-int(v), vi=1+v-int(v), ..., vi=v. + + References + ---------- + .. [1] Zhang, Shanjie and Jin, Jianming. "Computation of Special + Functions", John Wiley and Sons, 1996. + https://people.sc.fsu.edu/~jburkardt/f77_src/special_functions/special_functions.html + .. [2] Jahnke, E. and Emde, F. "Tables of Functions with Formulae and + Curves" (4th ed.), Dover, 1945 + """ + if not (isscalar(v) and isscalar(x)): + raise ValueError("arguments must be scalars.") + if (v < 0): + raise ValueError("argument must be > 0.") + n = int(v) + v0 = v - n + if (n < 1): + n1 = 1 + else: + n1 = n + v1 = n1 + v0 + if (v != floor(v)): + vm, vl, dl = _specfun.lamv(v1, x) + else: + vm, vl, dl = _specfun.lamn(v1, x) + return vl[:(n+1)], dl[:(n+1)] + + +def pbdv_seq(v, x): + """Parabolic cylinder functions Dv(x) and derivatives. + + Parameters + ---------- + v : float + Order of the parabolic cylinder function + x : float + Value at which to evaluate the function and derivatives + + Returns + ------- + dv : ndarray + Values of D_vi(x), for vi=v-int(v), vi=1+v-int(v), ..., vi=v. + dp : ndarray + Derivatives D_vi'(x), for vi=v-int(v), vi=1+v-int(v), ..., vi=v. + + References + ---------- + .. [1] Zhang, Shanjie and Jin, Jianming. "Computation of Special + Functions", John Wiley and Sons, 1996, chapter 13. + https://people.sc.fsu.edu/~jburkardt/f77_src/special_functions/special_functions.html + + """ + if not (isscalar(v) and isscalar(x)): + raise ValueError("arguments must be scalars.") + n = int(v) + v0 = v-n + if (n < 1): + n1 = 1 + else: + n1 = n + v1 = n1 + v0 + dv, dp, pdf, pdd = _specfun.pbdv(v1, x) + return dv[:n1+1], dp[:n1+1] + + +def pbvv_seq(v, x): + """Parabolic cylinder functions Vv(x) and derivatives. + + Parameters + ---------- + v : float + Order of the parabolic cylinder function + x : float + Value at which to evaluate the function and derivatives + + Returns + ------- + dv : ndarray + Values of V_vi(x), for vi=v-int(v), vi=1+v-int(v), ..., vi=v. + dp : ndarray + Derivatives V_vi'(x), for vi=v-int(v), vi=1+v-int(v), ..., vi=v. + + References + ---------- + .. [1] Zhang, Shanjie and Jin, Jianming. "Computation of Special + Functions", John Wiley and Sons, 1996, chapter 13. + https://people.sc.fsu.edu/~jburkardt/f77_src/special_functions/special_functions.html + + """ + if not (isscalar(v) and isscalar(x)): + raise ValueError("arguments must be scalars.") + n = int(v) + v0 = v-n + if (n <= 1): + n1 = 1 + else: + n1 = n + v1 = n1 + v0 + dv, dp, pdf, pdd = _specfun.pbvv(v1, x) + return dv[:n1+1], dp[:n1+1] + + +def pbdn_seq(n, z): + """Parabolic cylinder functions Dn(z) and derivatives. + + Parameters + ---------- + n : int + Order of the parabolic cylinder function + z : complex + Value at which to evaluate the function and derivatives + + Returns + ------- + dv : ndarray + Values of D_i(z), for i=0, ..., i=n. + dp : ndarray + Derivatives D_i'(z), for i=0, ..., i=n. + + References + ---------- + .. [1] Zhang, Shanjie and Jin, Jianming. "Computation of Special + Functions", John Wiley and Sons, 1996, chapter 13. + https://people.sc.fsu.edu/~jburkardt/f77_src/special_functions/special_functions.html + + """ + if not (isscalar(n) and isscalar(z)): + raise ValueError("arguments must be scalars.") + if (floor(n) != n): + raise ValueError("n must be an integer.") + if (abs(n) <= 1): + n1 = 1 + else: + n1 = n + cpb, cpd = _specfun.cpbdn(n1, z) + return cpb[:n1+1], cpd[:n1+1] + + +def ber_zeros(nt): + """Compute nt zeros of the Kelvin function ber. + + Parameters + ---------- + nt : int + Number of zeros to compute. Must be positive. + + Returns + ------- + ndarray + First `nt` zeros of the Kelvin function. + + See Also + -------- + ber + + References + ---------- + .. [1] Zhang, Shanjie and Jin, Jianming. "Computation of Special + Functions", John Wiley and Sons, 1996. + https://people.sc.fsu.edu/~jburkardt/f77_src/special_functions/special_functions.html + + """ + if not isscalar(nt) or (floor(nt) != nt) or (nt <= 0): + raise ValueError("nt must be positive integer scalar.") + return _specfun.klvnzo(nt, 1) + + +def bei_zeros(nt): + """Compute nt zeros of the Kelvin function bei. + + Parameters + ---------- + nt : int + Number of zeros to compute. Must be positive. + + Returns + ------- + ndarray + First `nt` zeros of the Kelvin function. + + See Also + -------- + bei + + References + ---------- + .. [1] Zhang, Shanjie and Jin, Jianming. "Computation of Special + Functions", John Wiley and Sons, 1996. + https://people.sc.fsu.edu/~jburkardt/f77_src/special_functions/special_functions.html + + """ + if not isscalar(nt) or (floor(nt) != nt) or (nt <= 0): + raise ValueError("nt must be positive integer scalar.") + return _specfun.klvnzo(nt, 2) + + +def ker_zeros(nt): + """Compute nt zeros of the Kelvin function ker. + + Parameters + ---------- + nt : int + Number of zeros to compute. Must be positive. + + Returns + ------- + ndarray + First `nt` zeros of the Kelvin function. + + See Also + -------- + ker + + References + ---------- + .. [1] Zhang, Shanjie and Jin, Jianming. "Computation of Special + Functions", John Wiley and Sons, 1996. + https://people.sc.fsu.edu/~jburkardt/f77_src/special_functions/special_functions.html + + """ + if not isscalar(nt) or (floor(nt) != nt) or (nt <= 0): + raise ValueError("nt must be positive integer scalar.") + return _specfun.klvnzo(nt, 3) + + +def kei_zeros(nt): + """Compute nt zeros of the Kelvin function kei. + + Parameters + ---------- + nt : int + Number of zeros to compute. Must be positive. + + Returns + ------- + ndarray + First `nt` zeros of the Kelvin function. + + See Also + -------- + kei + + References + ---------- + .. [1] Zhang, Shanjie and Jin, Jianming. "Computation of Special + Functions", John Wiley and Sons, 1996. + https://people.sc.fsu.edu/~jburkardt/f77_src/special_functions/special_functions.html + + """ + if not isscalar(nt) or (floor(nt) != nt) or (nt <= 0): + raise ValueError("nt must be positive integer scalar.") + return _specfun.klvnzo(nt, 4) + + +def berp_zeros(nt): + """Compute nt zeros of the derivative of the Kelvin function ber. + + Parameters + ---------- + nt : int + Number of zeros to compute. Must be positive. + + Returns + ------- + ndarray + First `nt` zeros of the derivative of the Kelvin function. + + See Also + -------- + ber, berp + + References + ---------- + .. [1] Zhang, Shanjie and Jin, Jianming. "Computation of Special + Functions", John Wiley and Sons, 1996. + https://people.sc.fsu.edu/~jburkardt/f77_src/special_functions/special_functions.html + + """ + if not isscalar(nt) or (floor(nt) != nt) or (nt <= 0): + raise ValueError("nt must be positive integer scalar.") + return _specfun.klvnzo(nt, 5) + + +def beip_zeros(nt): + """Compute nt zeros of the derivative of the Kelvin function bei. + + Parameters + ---------- + nt : int + Number of zeros to compute. Must be positive. + + Returns + ------- + ndarray + First `nt` zeros of the derivative of the Kelvin function. + + See Also + -------- + bei, beip + + References + ---------- + .. [1] Zhang, Shanjie and Jin, Jianming. "Computation of Special + Functions", John Wiley and Sons, 1996. + https://people.sc.fsu.edu/~jburkardt/f77_src/special_functions/special_functions.html + + """ + if not isscalar(nt) or (floor(nt) != nt) or (nt <= 0): + raise ValueError("nt must be positive integer scalar.") + return _specfun.klvnzo(nt, 6) + + +def kerp_zeros(nt): + """Compute nt zeros of the derivative of the Kelvin function ker. + + Parameters + ---------- + nt : int + Number of zeros to compute. Must be positive. + + Returns + ------- + ndarray + First `nt` zeros of the derivative of the Kelvin function. + + See Also + -------- + ker, kerp + + References + ---------- + .. [1] Zhang, Shanjie and Jin, Jianming. "Computation of Special + Functions", John Wiley and Sons, 1996. + https://people.sc.fsu.edu/~jburkardt/f77_src/special_functions/special_functions.html + + """ + if not isscalar(nt) or (floor(nt) != nt) or (nt <= 0): + raise ValueError("nt must be positive integer scalar.") + return _specfun.klvnzo(nt, 7) + + +def keip_zeros(nt): + """Compute nt zeros of the derivative of the Kelvin function kei. + + Parameters + ---------- + nt : int + Number of zeros to compute. Must be positive. + + Returns + ------- + ndarray + First `nt` zeros of the derivative of the Kelvin function. + + See Also + -------- + kei, keip + + References + ---------- + .. [1] Zhang, Shanjie and Jin, Jianming. "Computation of Special + Functions", John Wiley and Sons, 1996. + https://people.sc.fsu.edu/~jburkardt/f77_src/special_functions/special_functions.html + + """ + if not isscalar(nt) or (floor(nt) != nt) or (nt <= 0): + raise ValueError("nt must be positive integer scalar.") + return _specfun.klvnzo(nt, 8) + + +def kelvin_zeros(nt): + """Compute nt zeros of all Kelvin functions. + + Returned in a length-8 tuple of arrays of length nt. The tuple contains + the arrays of zeros of (ber, bei, ker, kei, ber', bei', ker', kei'). + + References + ---------- + .. [1] Zhang, Shanjie and Jin, Jianming. "Computation of Special + Functions", John Wiley and Sons, 1996. + https://people.sc.fsu.edu/~jburkardt/f77_src/special_functions/special_functions.html + + """ + if not isscalar(nt) or (floor(nt) != nt) or (nt <= 0): + raise ValueError("nt must be positive integer scalar.") + return (_specfun.klvnzo(nt, 1), + _specfun.klvnzo(nt, 2), + _specfun.klvnzo(nt, 3), + _specfun.klvnzo(nt, 4), + _specfun.klvnzo(nt, 5), + _specfun.klvnzo(nt, 6), + _specfun.klvnzo(nt, 7), + _specfun.klvnzo(nt, 8)) + + +def pro_cv_seq(m, n, c): + """Characteristic values for prolate spheroidal wave functions. + + Compute a sequence of characteristic values for the prolate + spheroidal wave functions for mode m and n'=m..n and spheroidal + parameter c. + + References + ---------- + .. [1] Zhang, Shanjie and Jin, Jianming. "Computation of Special + Functions", John Wiley and Sons, 1996. + https://people.sc.fsu.edu/~jburkardt/f77_src/special_functions/special_functions.html + + """ + if not (isscalar(m) and isscalar(n) and isscalar(c)): + raise ValueError("Arguments must be scalars.") + if (n != floor(n)) or (m != floor(m)): + raise ValueError("Modes must be integers.") + if (n-m > 199): + raise ValueError("Difference between n and m is too large.") + maxL = n-m+1 + return _specfun.segv(m, n, c, 1)[1][:maxL] + + +def obl_cv_seq(m, n, c): + """Characteristic values for oblate spheroidal wave functions. + + Compute a sequence of characteristic values for the oblate + spheroidal wave functions for mode m and n'=m..n and spheroidal + parameter c. + + References + ---------- + .. [1] Zhang, Shanjie and Jin, Jianming. "Computation of Special + Functions", John Wiley and Sons, 1996. + https://people.sc.fsu.edu/~jburkardt/f77_src/special_functions/special_functions.html + + """ + if not (isscalar(m) and isscalar(n) and isscalar(c)): + raise ValueError("Arguments must be scalars.") + if (n != floor(n)) or (m != floor(m)): + raise ValueError("Modes must be integers.") + if (n-m > 199): + raise ValueError("Difference between n and m is too large.") + maxL = n-m+1 + return _specfun.segv(m, n, c, -1)[1][:maxL] + + +@_deprecate_positional_args(version="1.14") +def comb(N, k, *, exact=False, repetition=False, legacy=_NoValue): + """The number of combinations of N things taken k at a time. + + This is often expressed as "N choose k". + + Parameters + ---------- + N : int, ndarray + Number of things. + k : int, ndarray + Number of elements taken. + exact : bool, optional + For integers, if `exact` is False, then floating point precision is + used, otherwise the result is computed exactly. For non-integers, if + `exact` is True, is disregarded. + repetition : bool, optional + If `repetition` is True, then the number of combinations with + repetition is computed. + legacy : bool, optional + If `legacy` is True and `exact` is True, then non-integral arguments + are cast to ints; if `legacy` is False, the result for non-integral + arguments is unaffected by the value of `exact`. + + .. deprecated:: 1.9.0 + Using `legacy` is deprecated and will removed by + Scipy 1.14.0. If you want to keep the legacy behaviour, cast + your inputs directly, e.g. + ``comb(int(your_N), int(your_k), exact=True)``. + + Returns + ------- + val : int, float, ndarray + The total number of combinations. + + See Also + -------- + binom : Binomial coefficient considered as a function of two real + variables. + + Notes + ----- + - Array arguments accepted only for exact=False case. + - If N < 0, or k < 0, then 0 is returned. + - If k > N and repetition=False, then 0 is returned. + + Examples + -------- + >>> import numpy as np + >>> from scipy.special import comb + >>> k = np.array([3, 4]) + >>> n = np.array([10, 10]) + >>> comb(n, k, exact=False) + array([ 120., 210.]) + >>> comb(10, 3, exact=True) + 120 + >>> comb(10, 3, exact=True, repetition=True) + 220 + + """ + if legacy is not _NoValue: + warnings.warn( + "Using 'legacy' keyword is deprecated and will be removed by " + "Scipy 1.14.0. If you want to keep the legacy behaviour, cast " + "your inputs directly, e.g. " + "'comb(int(your_N), int(your_k), exact=True)'.", + DeprecationWarning, + stacklevel=2 + ) + if repetition: + return comb(N + k - 1, k, exact=exact, legacy=legacy) + if exact: + if int(N) == N and int(k) == k: + # _comb_int casts inputs to integers, which is safe & intended here + return _comb_int(N, k) + elif legacy: + # here at least one number is not an integer; legacy behavior uses + # lossy casts to int + return _comb_int(N, k) + # otherwise, we disregard `exact=True`; it makes no sense for + # non-integral arguments + return comb(N, k) + else: + k, N = asarray(k), asarray(N) + cond = (k <= N) & (N >= 0) & (k >= 0) + vals = binom(N, k) + if isinstance(vals, np.ndarray): + vals[~cond] = 0 + elif not cond: + vals = np.float64(0) + return vals + + +def perm(N, k, exact=False): + """Permutations of N things taken k at a time, i.e., k-permutations of N. + + It's also known as "partial permutations". + + Parameters + ---------- + N : int, ndarray + Number of things. + k : int, ndarray + Number of elements taken. + exact : bool, optional + If `exact` is False, then floating point precision is used, otherwise + exact long integer is computed. + + Returns + ------- + val : int, ndarray + The number of k-permutations of N. + + Notes + ----- + - Array arguments accepted only for exact=False case. + - If k > N, N < 0, or k < 0, then a 0 is returned. + + Examples + -------- + >>> import numpy as np + >>> from scipy.special import perm + >>> k = np.array([3, 4]) + >>> n = np.array([10, 10]) + >>> perm(n, k) + array([ 720., 5040.]) + >>> perm(10, 3, exact=True) + 720 + + """ + if exact: + if (k > N) or (N < 0) or (k < 0): + return 0 + val = 1 + for i in range(N - k + 1, N + 1): + val *= i + return val + else: + k, N = asarray(k), asarray(N) + cond = (k <= N) & (N >= 0) & (k >= 0) + vals = poch(N - k + 1, k) + if isinstance(vals, np.ndarray): + vals[~cond] = 0 + elif not cond: + vals = np.float64(0) + return vals + + +# https://stackoverflow.com/a/16327037 +def _range_prod(lo, hi, k=1): + """ + Product of a range of numbers spaced k apart (from hi). + + For k=1, this returns the product of + lo * (lo+1) * (lo+2) * ... * (hi-2) * (hi-1) * hi + = hi! / (lo-1)! + + For k>1, it correspond to taking only every k'th number when + counting down from hi - e.g. 18!!!! = _range_prod(1, 18, 4). + + Breaks into smaller products first for speed: + _range_prod(2, 9) = ((2*3)*(4*5))*((6*7)*(8*9)) + """ + if lo + k < hi: + mid = (hi + lo) // 2 + if k > 1: + # make sure mid is a multiple of k away from hi + mid = mid - ((mid - hi) % k) + return _range_prod(lo, mid, k) * _range_prod(mid + k, hi, k) + elif lo + k == hi: + return lo * hi + else: + return hi + + +def _factorialx_array_exact(n, k=1): + """ + Exact computation of factorial for an array. + + The factorials are computed in incremental fashion, by taking + the sorted unique values of n and multiplying the intervening + numbers between the different unique values. + + In other words, the factorial for the largest input is only + computed once, with each other result computed in the process. + + k > 1 corresponds to the multifactorial. + """ + un = np.unique(n) + # numpy changed nan-sorting behaviour with 1.21, see numpy/numpy#18070; + # to unify the behaviour, we remove the nan's here; the respective + # values will be set separately at the end + un = un[~np.isnan(un)] + + # Convert to object array if np.int64 can't handle size + if np.isnan(n).any(): + dt = float + elif k in _FACTORIALK_LIMITS_64BITS.keys(): + if un[-1] > _FACTORIALK_LIMITS_64BITS[k]: + # e.g. k=1: 21! > np.iinfo(np.int64).max + dt = object + elif un[-1] > _FACTORIALK_LIMITS_32BITS[k]: + # e.g. k=3: 26!!! > np.iinfo(np.int32).max + dt = np.int64 + else: + dt = np.dtype("long") + else: + # for k >= 10, we always use object + dt = object + + out = np.empty_like(n, dtype=dt) + + # Handle invalid/trivial values + un = un[un > 1] + out[n < 2] = 1 + out[n < 0] = 0 + + # Calculate products of each range of numbers + # we can only multiply incrementally if the values are k apart; + # therefore we partition `un` into "lanes", i.e. its residues modulo k + for lane in range(0, k): + ul = un[(un % k) == lane] if k > 1 else un + if ul.size: + # after np.unique, un resp. ul are sorted, ul[0] is the smallest; + # cast to python ints to avoid overflow with np.int-types + val = _range_prod(1, int(ul[0]), k=k) + out[n == ul[0]] = val + for i in range(len(ul) - 1): + # by the filtering above, we have ensured that prev & current + # are a multiple of k apart + prev = ul[i] + current = ul[i + 1] + # we already multiplied all factors until prev; continue + # building the full factorial from the following (`prev + 1`); + # use int() for the same reason as above + val *= _range_prod(int(prev + 1), int(current), k=k) + out[n == current] = val + + if np.isnan(n).any(): + out = out.astype(np.float64) + out[np.isnan(n)] = np.nan + return out + + +def _factorialx_array_approx(n, k): + """ + Calculate approximation to multifactorial for array n and integer k. + + Ensure we only call _factorialx_approx_core where necessary/required. + """ + result = zeros(n.shape) + # keep nans as nans + place(result, np.isnan(n), np.nan) + # only compute where n >= 0 (excludes nans), everything else is 0 + cond = (n >= 0) + n_to_compute = extract(cond, n) + place(result, cond, _factorialx_approx_core(n_to_compute, k=k)) + return result + + +def _factorialx_approx_core(n, k): + """ + Core approximation to multifactorial for array n and integer k. + """ + if k == 1: + # shortcut for k=1 + result = gamma(n + 1) + if isinstance(n, np.ndarray): + # gamma does not maintain 0-dim arrays + result = np.array(result) + return result + + n_mod_k = n % k + # scalar case separately, unified handling would be inefficient for arrays; + # don't use isscalar due to numpy/numpy#23574; 0-dim arrays treated below + if not isinstance(n, np.ndarray): + return ( + np.power(k, (n - n_mod_k) / k) + * gamma(n / k + 1) / gamma(n_mod_k / k + 1) + * max(n_mod_k, 1) + ) + + # factor that's independent of the residue class (see factorialk docstring) + result = np.power(k, n / k) * gamma(n / k + 1) + # factor dependent on residue r (for `r=0` it's 1, so we skip `r=0` + # below and thus also avoid evaluating `max(r, 1)`) + def corr(k, r): return np.power(k, -r / k) / gamma(r / k + 1) * r + for r in np.unique(n_mod_k): + if r == 0: + continue + result[n_mod_k == r] *= corr(k, r) + return result + + +def factorial(n, exact=False): + """ + The factorial of a number or array of numbers. + + The factorial of non-negative integer `n` is the product of all + positive integers less than or equal to `n`:: + + n! = n * (n - 1) * (n - 2) * ... * 1 + + Parameters + ---------- + n : int or array_like of ints + Input values. If ``n < 0``, the return value is 0. + exact : bool, optional + If True, calculate the answer exactly using long integer arithmetic. + If False, result is approximated in floating point rapidly using the + `gamma` function. + Default is False. + + Returns + ------- + nf : float or int or ndarray + Factorial of `n`, as integer or float depending on `exact`. + + Notes + ----- + For arrays with ``exact=True``, the factorial is computed only once, for + the largest input, with each other result computed in the process. + The output dtype is increased to ``int64`` or ``object`` if necessary. + + With ``exact=False`` the factorial is approximated using the gamma + function: + + .. math:: n! = \\Gamma(n+1) + + Examples + -------- + >>> import numpy as np + >>> from scipy.special import factorial + >>> arr = np.array([3, 4, 5]) + >>> factorial(arr, exact=False) + array([ 6., 24., 120.]) + >>> factorial(arr, exact=True) + array([ 6, 24, 120]) + >>> factorial(5, exact=True) + 120 + + """ + # don't use isscalar due to numpy/numpy#23574; 0-dim arrays treated below + if np.ndim(n) == 0 and not isinstance(n, np.ndarray): + # scalar cases + if n is None or np.isnan(n): + return np.nan + elif not (np.issubdtype(type(n), np.integer) + or np.issubdtype(type(n), np.floating)): + raise ValueError( + f"Unsupported datatype for factorial: {type(n)}\n" + "Permitted data types are integers and floating point numbers" + ) + elif n < 0: + return 0 + elif exact and np.issubdtype(type(n), np.integer): + return math.factorial(n) + elif exact: + msg = ("Non-integer values of `n` together with `exact=True` are " + "deprecated. Either ensure integer `n` or use `exact=False`.") + warnings.warn(msg, DeprecationWarning, stacklevel=2) + return _factorialx_approx_core(n, k=1) + + # arrays & array-likes + n = asarray(n) + if n.size == 0: + # return empty arrays unchanged + return n + if not (np.issubdtype(n.dtype, np.integer) + or np.issubdtype(n.dtype, np.floating)): + raise ValueError( + f"Unsupported datatype for factorial: {n.dtype}\n" + "Permitted data types are integers and floating point numbers" + ) + if exact and not np.issubdtype(n.dtype, np.integer): + msg = ("factorial with `exact=True` does not " + "support non-integral arrays") + raise ValueError(msg) + + if exact: + return _factorialx_array_exact(n, k=1) + return _factorialx_array_approx(n, k=1) + + +def factorial2(n, exact=False): + """Double factorial. + + This is the factorial with every second value skipped. E.g., ``7!! = 7 * 5 + * 3 * 1``. It can be approximated numerically as:: + + n!! = 2 ** (n / 2) * gamma(n / 2 + 1) * sqrt(2 / pi) n odd + = 2 ** (n / 2) * gamma(n / 2 + 1) n even + = 2 ** (n / 2) * (n / 2)! n even + + Parameters + ---------- + n : int or array_like + Calculate ``n!!``. If ``n < 0``, the return value is 0. + exact : bool, optional + The result can be approximated rapidly using the gamma-formula + above (default). If `exact` is set to True, calculate the + answer exactly using integer arithmetic. + + Returns + ------- + nff : float or int + Double factorial of `n`, as an int or a float depending on + `exact`. + + Examples + -------- + >>> from scipy.special import factorial2 + >>> factorial2(7, exact=False) + array(105.00000000000001) + >>> factorial2(7, exact=True) + 105 + + """ + + # don't use isscalar due to numpy/numpy#23574; 0-dim arrays treated below + if np.ndim(n) == 0 and not isinstance(n, np.ndarray): + # scalar cases + if n is None or np.isnan(n): + return np.nan + elif not np.issubdtype(type(n), np.integer): + msg = "factorial2 does not support non-integral scalar arguments" + raise ValueError(msg) + elif n < 0: + return 0 + elif n in {0, 1}: + return 1 + # general integer case + if exact: + return _range_prod(1, n, k=2) + return _factorialx_approx_core(n, k=2) + # arrays & array-likes + n = asarray(n) + if n.size == 0: + # return empty arrays unchanged + return n + if not np.issubdtype(n.dtype, np.integer): + raise ValueError("factorial2 does not support non-integral arrays") + if exact: + return _factorialx_array_exact(n, k=2) + return _factorialx_array_approx(n, k=2) + + +def factorialk(n, k, exact=None): + """Multifactorial of n of order k, n(!!...!). + + This is the multifactorial of n skipping k values. For example, + + factorialk(17, 4) = 17!!!! = 17 * 13 * 9 * 5 * 1 + + In particular, for any integer ``n``, we have + + factorialk(n, 1) = factorial(n) + + factorialk(n, 2) = factorial2(n) + + Parameters + ---------- + n : int or array_like + Calculate multifactorial. If ``n < 0``, the return value is 0. + k : int + Order of multifactorial. + exact : bool, optional + If exact is set to True, calculate the answer exactly using + integer arithmetic, otherwise use an approximation (faster, + but yields floats instead of integers) + + .. warning:: + The default value for ``exact`` will be changed to + ``False`` in SciPy 1.15.0. + + Returns + ------- + val : int + Multifactorial of `n`. + + Examples + -------- + >>> from scipy.special import factorialk + >>> factorialk(5, k=1, exact=True) + 120 + >>> factorialk(5, k=3, exact=True) + 10 + >>> factorialk([5, 7, 9], k=3, exact=True) + array([ 10, 28, 162]) + >>> factorialk([5, 7, 9], k=3, exact=False) + array([ 10., 28., 162.]) + + Notes + ----- + While less straight-forward than for the double-factorial, it's possible to + calculate a general approximation formula of n!(k) by studying ``n`` for a given + remainder ``r < k`` (thus ``n = m * k + r``, resp. ``r = n % k``), which can be + put together into something valid for all integer values ``n >= 0`` & ``k > 0``:: + + n!(k) = k ** ((n - r)/k) * gamma(n/k + 1) / gamma(r/k + 1) * max(r, 1) + + This is the basis of the approximation when ``exact=False``. Compare also [1]. + + References + ---------- + .. [1] Complex extension to multifactorial + https://en.wikipedia.org/wiki/Double_factorial#Alternative_extension_of_the_multifactorial + """ + if not np.issubdtype(type(k), np.integer) or k < 1: + raise ValueError(f"k must be a positive integer, received: {k}") + if exact is None: + msg = ( + "factorialk will default to `exact=False` starting from SciPy " + "1.15.0. To avoid behaviour changes due to this, explicitly " + "specify either `exact=False` (faster, returns floats), or the " + "past default `exact=True` (slower, lossless result as integer)." + ) + warnings.warn(msg, DeprecationWarning, stacklevel=2) + exact = True + + helpmsg = "" + if k in {1, 2}: + func = "factorial" if k == 1 else "factorial2" + helpmsg = f"\nYou can try to use {func} instead" + + # don't use isscalar due to numpy/numpy#23574; 0-dim arrays treated below + if np.ndim(n) == 0 and not isinstance(n, np.ndarray): + # scalar cases + if n is None or np.isnan(n): + return np.nan + elif not np.issubdtype(type(n), np.integer): + msg = "factorialk does not support non-integral scalar arguments!" + raise ValueError(msg + helpmsg) + elif n < 0: + return 0 + elif n in {0, 1}: + return 1 + # general integer case + if exact: + return _range_prod(1, n, k=k) + return _factorialx_approx_core(n, k=k) + # arrays & array-likes + n = asarray(n) + if n.size == 0: + # return empty arrays unchanged + return n + if not np.issubdtype(n.dtype, np.integer): + msg = "factorialk does not support non-integral arrays!" + raise ValueError(msg + helpmsg) + if exact: + return _factorialx_array_exact(n, k=k) + return _factorialx_array_approx(n, k=k) + + +def stirling2(N, K, *, exact=False): + r"""Generate Stirling number(s) of the second kind. + + Stirling numbers of the second kind count the number of ways to + partition a set with N elements into K non-empty subsets. + + The values this function returns are calculated using a dynamic + program which avoids redundant computation across the subproblems + in the solution. For array-like input, this implementation also + avoids redundant computation across the different Stirling number + calculations. + + The numbers are sometimes denoted + + .. math:: + + {N \brace{K}} + + see [1]_ for details. This is often expressed-verbally-as + "N subset K". + + Parameters + ---------- + N : int, ndarray + Number of things. + K : int, ndarray + Number of non-empty subsets taken. + exact : bool, optional + Uses dynamic programming (DP) with floating point + numbers for smaller arrays and uses a second order approximation due to + Temme for larger entries of `N` and `K` that allows trading speed for + accuracy. See [2]_ for a description. Temme approximation is used for + values `n>50`. The max error from the DP has max relative error + `4.5*10^-16` for `n<=50` and the max error from the Temme approximation + has max relative error `5*10^-5` for `51 <= n < 70` and + `9*10^-6` for `70 <= n < 101`. Note that these max relative errors will + decrease further as `n` increases. + + Returns + ------- + val : int, float, ndarray + The number of partitions. + + See Also + -------- + comb : The number of combinations of N things taken k at a time. + + Notes + ----- + - If N < 0, or K < 0, then 0 is returned. + - If K > N, then 0 is returned. + + The output type will always be `int` or ndarray of `object`. + The input must contain either numpy or python integers otherwise a + TypeError is raised. + + References + ---------- + .. [1] R. L. Graham, D. E. Knuth and O. Patashnik, "Concrete + Mathematics: A Foundation for Computer Science," Addison-Wesley + Publishing Company, Boston, 1989. Chapter 6, page 258. + + .. [2] Temme, Nico M. "Asymptotic estimates of Stirling numbers." + Studies in Applied Mathematics 89.3 (1993): 233-243. + + Examples + -------- + >>> import numpy as np + >>> from scipy.special import stirling2 + >>> k = np.array([3, -1, 3]) + >>> n = np.array([10, 10, 9]) + >>> stirling2(n, k) + array([9330, 0, 3025], dtype=object) + + """ + output_is_scalar = np.isscalar(N) and np.isscalar(K) + # make a min-heap of unique (n,k) pairs + N, K = asarray(N), asarray(K) + if not np.issubdtype(N.dtype, np.integer): + raise TypeError("Argument `N` must contain only integers") + if not np.issubdtype(K.dtype, np.integer): + raise TypeError("Argument `K` must contain only integers") + if not exact: + # NOTE: here we allow np.uint via casting to double types prior to + # passing to private ufunc dispatcher. All dispatched functions + # take double type for (n,k) arguments and return double. + return _stirling2_inexact(N.astype(float), K.astype(float)) + nk_pairs = list( + set([(n.take(0), k.take(0)) + for n, k in np.nditer([N, K], ['refs_ok'])]) + ) + heapify(nk_pairs) + # base mapping for small values + snsk_vals = defaultdict(int) + for pair in [(0, 0), (1, 1), (2, 1), (2, 2)]: + snsk_vals[pair] = 1 + # for each pair in the min-heap, calculate the value, store for later + n_old, n_row = 2, [0, 1, 1] + while nk_pairs: + n, k = heappop(nk_pairs) + if n < 2 or k > n or k <= 0: + continue + elif k == n or k == 1: + snsk_vals[(n, k)] = 1 + continue + elif n != n_old: + num_iters = n - n_old + while num_iters > 0: + n_row.append(1) + # traverse from back to remove second row + for j in range(len(n_row)-2, 1, -1): + n_row[j] = n_row[j]*j + n_row[j-1] + num_iters -= 1 + snsk_vals[(n, k)] = n_row[k] + else: + snsk_vals[(n, k)] = n_row[k] + n_old, n_row = n, n_row + out_types = [object, object, object] if exact else [float, float, float] + # for each pair in the map, fetch the value, and populate the array + it = np.nditer( + [N, K, None], + ['buffered', 'refs_ok'], + [['readonly'], ['readonly'], ['writeonly', 'allocate']], + op_dtypes=out_types, + ) + with it: + while not it.finished: + it[2] = snsk_vals[(int(it[0]), int(it[1]))] + it.iternext() + output = it.operands[2] + # If N and K were both scalars, convert output to scalar. + if output_is_scalar: + output = output.take(0) + return output + + +def zeta(x, q=None, out=None): + r""" + Riemann or Hurwitz zeta function. + + Parameters + ---------- + x : array_like of float + Input data, must be real + q : array_like of float, optional + Input data, must be real. Defaults to Riemann zeta. + out : ndarray, optional + Output array for the computed values. + + Returns + ------- + out : array_like + Values of zeta(x). + + See Also + -------- + zetac + + Notes + ----- + The two-argument version is the Hurwitz zeta function + + .. math:: + + \zeta(x, q) = \sum_{k=0}^{\infty} \frac{1}{(k + q)^x}; + + see [dlmf]_ for details. The Riemann zeta function corresponds to + the case when ``q = 1``. + + References + ---------- + .. [dlmf] NIST, Digital Library of Mathematical Functions, + https://dlmf.nist.gov/25.11#i + + Examples + -------- + >>> import numpy as np + >>> from scipy.special import zeta, polygamma, factorial + + Some specific values: + + >>> zeta(2), np.pi**2/6 + (1.6449340668482266, 1.6449340668482264) + + >>> zeta(4), np.pi**4/90 + (1.0823232337111381, 1.082323233711138) + + Relation to the `polygamma` function: + + >>> m = 3 + >>> x = 1.25 + >>> polygamma(m, x) + array(2.782144009188397) + >>> (-1)**(m+1) * factorial(m) * zeta(m+1, x) + 2.7821440091883969 + + """ + if q is None: + return _ufuncs._riemann_zeta(x, out) + else: + return _ufuncs._zeta(x, q, out)