diff --git "a/llmeval-env/lib/python3.10/site-packages/scipy/stats/_distn_infrastructure.py" "b/llmeval-env/lib/python3.10/site-packages/scipy/stats/_distn_infrastructure.py" new file mode 100644--- /dev/null +++ "b/llmeval-env/lib/python3.10/site-packages/scipy/stats/_distn_infrastructure.py" @@ -0,0 +1,4098 @@ +# +# Author: Travis Oliphant 2002-2011 with contributions from +# SciPy Developers 2004-2011 +# +from scipy._lib._util import getfullargspec_no_self as _getfullargspec + +import sys +import keyword +import re +import types +import warnings +from itertools import zip_longest + +from scipy._lib import doccer +from ._distr_params import distcont, distdiscrete +from scipy._lib._util import check_random_state + +from scipy.special import comb, entr + + +# for root finding for continuous distribution ppf, and maximum likelihood +# estimation +from scipy import optimize + +# for functions of continuous distributions (e.g. moments, entropy, cdf) +from scipy import integrate + +# to approximate the pdf of a continuous distribution given its cdf +from scipy._lib._finite_differences import _derivative + +# for scipy.stats.entropy. Attempts to import just that function or file +# have cause import problems +from scipy import stats + +from numpy import (arange, putmask, ones, shape, ndarray, zeros, floor, + logical_and, log, sqrt, place, argmax, vectorize, asarray, + nan, inf, isinf, empty) + +import numpy as np +from ._constants import _XMAX, _LOGXMAX +from ._censored_data import CensoredData +from scipy.stats._warnings_errors import FitError + +# These are the docstring parts used for substitution in specific +# distribution docstrings + +docheaders = {'methods': """\nMethods\n-------\n""", + 'notes': """\nNotes\n-----\n""", + 'examples': """\nExamples\n--------\n"""} + +_doc_rvs = """\ +rvs(%(shapes)s, loc=0, scale=1, size=1, random_state=None) + Random variates. +""" +_doc_pdf = """\ +pdf(x, %(shapes)s, loc=0, scale=1) + Probability density function. +""" +_doc_logpdf = """\ +logpdf(x, %(shapes)s, loc=0, scale=1) + Log of the probability density function. +""" +_doc_pmf = """\ +pmf(k, %(shapes)s, loc=0, scale=1) + Probability mass function. +""" +_doc_logpmf = """\ +logpmf(k, %(shapes)s, loc=0, scale=1) + Log of the probability mass function. +""" +_doc_cdf = """\ +cdf(x, %(shapes)s, loc=0, scale=1) + Cumulative distribution function. +""" +_doc_logcdf = """\ +logcdf(x, %(shapes)s, loc=0, scale=1) + Log of the cumulative distribution function. +""" +_doc_sf = """\ +sf(x, %(shapes)s, loc=0, scale=1) + Survival function (also defined as ``1 - cdf``, but `sf` is sometimes more accurate). +""" # noqa: E501 +_doc_logsf = """\ +logsf(x, %(shapes)s, loc=0, scale=1) + Log of the survival function. +""" +_doc_ppf = """\ +ppf(q, %(shapes)s, loc=0, scale=1) + Percent point function (inverse of ``cdf`` --- percentiles). +""" +_doc_isf = """\ +isf(q, %(shapes)s, loc=0, scale=1) + Inverse survival function (inverse of ``sf``). +""" +_doc_moment = """\ +moment(order, %(shapes)s, loc=0, scale=1) + Non-central moment of the specified order. +""" +_doc_stats = """\ +stats(%(shapes)s, loc=0, scale=1, moments='mv') + Mean('m'), variance('v'), skew('s'), and/or kurtosis('k'). +""" +_doc_entropy = """\ +entropy(%(shapes)s, loc=0, scale=1) + (Differential) entropy of the RV. +""" +_doc_fit = """\ +fit(data) + Parameter estimates for generic data. + See `scipy.stats.rv_continuous.fit `__ for detailed documentation of the + keyword arguments. +""" # noqa: E501 +_doc_expect = """\ +expect(func, args=(%(shapes_)s), loc=0, scale=1, lb=None, ub=None, conditional=False, **kwds) + Expected value of a function (of one argument) with respect to the distribution. +""" # noqa: E501 +_doc_expect_discrete = """\ +expect(func, args=(%(shapes_)s), loc=0, lb=None, ub=None, conditional=False) + Expected value of a function (of one argument) with respect to the distribution. +""" +_doc_median = """\ +median(%(shapes)s, loc=0, scale=1) + Median of the distribution. +""" +_doc_mean = """\ +mean(%(shapes)s, loc=0, scale=1) + Mean of the distribution. +""" +_doc_var = """\ +var(%(shapes)s, loc=0, scale=1) + Variance of the distribution. +""" +_doc_std = """\ +std(%(shapes)s, loc=0, scale=1) + Standard deviation of the distribution. +""" +_doc_interval = """\ +interval(confidence, %(shapes)s, loc=0, scale=1) + Confidence interval with equal areas around the median. +""" +_doc_allmethods = ''.join([docheaders['methods'], _doc_rvs, _doc_pdf, + _doc_logpdf, _doc_cdf, _doc_logcdf, _doc_sf, + _doc_logsf, _doc_ppf, _doc_isf, _doc_moment, + _doc_stats, _doc_entropy, _doc_fit, + _doc_expect, _doc_median, + _doc_mean, _doc_var, _doc_std, _doc_interval]) + +_doc_default_longsummary = """\ +As an instance of the `rv_continuous` class, `%(name)s` object inherits from it +a collection of generic methods (see below for the full list), +and completes them with details specific for this particular distribution. +""" + +_doc_default_frozen_note = """ +Alternatively, the object may be called (as a function) to fix the shape, +location, and scale parameters returning a "frozen" continuous RV object: + +rv = %(name)s(%(shapes)s, loc=0, scale=1) + - Frozen RV object with the same methods but holding the given shape, + location, and scale fixed. +""" +_doc_default_example = """\ +Examples +-------- +>>> import numpy as np +>>> from scipy.stats import %(name)s +>>> import matplotlib.pyplot as plt +>>> fig, ax = plt.subplots(1, 1) + +Calculate the first four moments: + +%(set_vals_stmt)s +>>> mean, var, skew, kurt = %(name)s.stats(%(shapes)s, moments='mvsk') + +Display the probability density function (``pdf``): + +>>> x = np.linspace(%(name)s.ppf(0.01, %(shapes)s), +... %(name)s.ppf(0.99, %(shapes)s), 100) +>>> ax.plot(x, %(name)s.pdf(x, %(shapes)s), +... 'r-', lw=5, alpha=0.6, label='%(name)s pdf') + +Alternatively, the distribution object can be called (as a function) +to fix the shape, location and scale parameters. This returns a "frozen" +RV object holding the given parameters fixed. + +Freeze the distribution and display the frozen ``pdf``: + +>>> rv = %(name)s(%(shapes)s) +>>> ax.plot(x, rv.pdf(x), 'k-', lw=2, label='frozen pdf') + +Check accuracy of ``cdf`` and ``ppf``: + +>>> vals = %(name)s.ppf([0.001, 0.5, 0.999], %(shapes)s) +>>> np.allclose([0.001, 0.5, 0.999], %(name)s.cdf(vals, %(shapes)s)) +True + +Generate random numbers: + +>>> r = %(name)s.rvs(%(shapes)s, size=1000) + +And compare the histogram: + +>>> ax.hist(r, density=True, bins='auto', histtype='stepfilled', alpha=0.2) +>>> ax.set_xlim([x[0], x[-1]]) +>>> ax.legend(loc='best', frameon=False) +>>> plt.show() + +""" + +_doc_default_locscale = """\ +The probability density above is defined in the "standardized" form. To shift +and/or scale the distribution use the ``loc`` and ``scale`` parameters. +Specifically, ``%(name)s.pdf(x, %(shapes)s, loc, scale)`` is identically +equivalent to ``%(name)s.pdf(y, %(shapes)s) / scale`` with +``y = (x - loc) / scale``. Note that shifting the location of a distribution +does not make it a "noncentral" distribution; noncentral generalizations of +some distributions are available in separate classes. +""" + +_doc_default = ''.join([_doc_default_longsummary, + _doc_allmethods, + '\n', + _doc_default_example]) + +_doc_default_before_notes = ''.join([_doc_default_longsummary, + _doc_allmethods]) + +docdict = { + 'rvs': _doc_rvs, + 'pdf': _doc_pdf, + 'logpdf': _doc_logpdf, + 'cdf': _doc_cdf, + 'logcdf': _doc_logcdf, + 'sf': _doc_sf, + 'logsf': _doc_logsf, + 'ppf': _doc_ppf, + 'isf': _doc_isf, + 'stats': _doc_stats, + 'entropy': _doc_entropy, + 'fit': _doc_fit, + 'moment': _doc_moment, + 'expect': _doc_expect, + 'interval': _doc_interval, + 'mean': _doc_mean, + 'std': _doc_std, + 'var': _doc_var, + 'median': _doc_median, + 'allmethods': _doc_allmethods, + 'longsummary': _doc_default_longsummary, + 'frozennote': _doc_default_frozen_note, + 'example': _doc_default_example, + 'default': _doc_default, + 'before_notes': _doc_default_before_notes, + 'after_notes': _doc_default_locscale +} + +# Reuse common content between continuous and discrete docs, change some +# minor bits. +docdict_discrete = docdict.copy() + +docdict_discrete['pmf'] = _doc_pmf +docdict_discrete['logpmf'] = _doc_logpmf +docdict_discrete['expect'] = _doc_expect_discrete +_doc_disc_methods = ['rvs', 'pmf', 'logpmf', 'cdf', 'logcdf', 'sf', 'logsf', + 'ppf', 'isf', 'stats', 'entropy', 'expect', 'median', + 'mean', 'var', 'std', 'interval'] +for obj in _doc_disc_methods: + docdict_discrete[obj] = docdict_discrete[obj].replace(', scale=1', '') + +_doc_disc_methods_err_varname = ['cdf', 'logcdf', 'sf', 'logsf'] +for obj in _doc_disc_methods_err_varname: + docdict_discrete[obj] = docdict_discrete[obj].replace('(x, ', '(k, ') + +docdict_discrete.pop('pdf') +docdict_discrete.pop('logpdf') + +_doc_allmethods = ''.join([docdict_discrete[obj] for obj in _doc_disc_methods]) +docdict_discrete['allmethods'] = docheaders['methods'] + _doc_allmethods + +docdict_discrete['longsummary'] = _doc_default_longsummary.replace( + 'rv_continuous', 'rv_discrete') + +_doc_default_frozen_note = """ +Alternatively, the object may be called (as a function) to fix the shape and +location parameters returning a "frozen" discrete RV object: + +rv = %(name)s(%(shapes)s, loc=0) + - Frozen RV object with the same methods but holding the given shape and + location fixed. +""" +docdict_discrete['frozennote'] = _doc_default_frozen_note + +_doc_default_discrete_example = """\ +Examples +-------- +>>> import numpy as np +>>> from scipy.stats import %(name)s +>>> import matplotlib.pyplot as plt +>>> fig, ax = plt.subplots(1, 1) + +Calculate the first four moments: + +%(set_vals_stmt)s +>>> mean, var, skew, kurt = %(name)s.stats(%(shapes)s, moments='mvsk') + +Display the probability mass function (``pmf``): + +>>> x = np.arange(%(name)s.ppf(0.01, %(shapes)s), +... %(name)s.ppf(0.99, %(shapes)s)) +>>> ax.plot(x, %(name)s.pmf(x, %(shapes)s), 'bo', ms=8, label='%(name)s pmf') +>>> ax.vlines(x, 0, %(name)s.pmf(x, %(shapes)s), colors='b', lw=5, alpha=0.5) + +Alternatively, the distribution object can be called (as a function) +to fix the shape and location. This returns a "frozen" RV object holding +the given parameters fixed. + +Freeze the distribution and display the frozen ``pmf``: + +>>> rv = %(name)s(%(shapes)s) +>>> ax.vlines(x, 0, rv.pmf(x), colors='k', linestyles='-', lw=1, +... label='frozen pmf') +>>> ax.legend(loc='best', frameon=False) +>>> plt.show() + +Check accuracy of ``cdf`` and ``ppf``: + +>>> prob = %(name)s.cdf(x, %(shapes)s) +>>> np.allclose(x, %(name)s.ppf(prob, %(shapes)s)) +True + +Generate random numbers: + +>>> r = %(name)s.rvs(%(shapes)s, size=1000) +""" + + +_doc_default_discrete_locscale = """\ +The probability mass function above is defined in the "standardized" form. +To shift distribution use the ``loc`` parameter. +Specifically, ``%(name)s.pmf(k, %(shapes)s, loc)`` is identically +equivalent to ``%(name)s.pmf(k - loc, %(shapes)s)``. +""" + +docdict_discrete['example'] = _doc_default_discrete_example +docdict_discrete['after_notes'] = _doc_default_discrete_locscale + +_doc_default_before_notes = ''.join([docdict_discrete['longsummary'], + docdict_discrete['allmethods']]) +docdict_discrete['before_notes'] = _doc_default_before_notes + +_doc_default_disc = ''.join([docdict_discrete['longsummary'], + docdict_discrete['allmethods'], + docdict_discrete['frozennote'], + docdict_discrete['example']]) +docdict_discrete['default'] = _doc_default_disc + +# clean up all the separate docstring elements, we do not need them anymore +for obj in [s for s in dir() if s.startswith('_doc_')]: + exec('del ' + obj) +del obj + + +def _moment(data, n, mu=None): + if mu is None: + mu = data.mean() + return ((data - mu)**n).mean() + + +def _moment_from_stats(n, mu, mu2, g1, g2, moment_func, args): + if (n == 0): + return 1.0 + elif (n == 1): + if mu is None: + val = moment_func(1, *args) + else: + val = mu + elif (n == 2): + if mu2 is None or mu is None: + val = moment_func(2, *args) + else: + val = mu2 + mu*mu + elif (n == 3): + if g1 is None or mu2 is None or mu is None: + val = moment_func(3, *args) + else: + mu3 = g1 * np.power(mu2, 1.5) # 3rd central moment + val = mu3+3*mu*mu2+mu*mu*mu # 3rd non-central moment + elif (n == 4): + if g1 is None or g2 is None or mu2 is None or mu is None: + val = moment_func(4, *args) + else: + mu4 = (g2+3.0)*(mu2**2.0) # 4th central moment + mu3 = g1*np.power(mu2, 1.5) # 3rd central moment + val = mu4+4*mu*mu3+6*mu*mu*mu2+mu*mu*mu*mu + else: + val = moment_func(n, *args) + + return val + + +def _skew(data): + """ + skew is third central moment / variance**(1.5) + """ + data = np.ravel(data) + mu = data.mean() + m2 = ((data - mu)**2).mean() + m3 = ((data - mu)**3).mean() + return m3 / np.power(m2, 1.5) + + +def _kurtosis(data): + """kurtosis is fourth central moment / variance**2 - 3.""" + data = np.ravel(data) + mu = data.mean() + m2 = ((data - mu)**2).mean() + m4 = ((data - mu)**4).mean() + return m4 / m2**2 - 3 + + +def _fit_determine_optimizer(optimizer): + if not callable(optimizer) and isinstance(optimizer, str): + if not optimizer.startswith('fmin_'): + optimizer = "fmin_"+optimizer + if optimizer == 'fmin_': + optimizer = 'fmin' + try: + optimizer = getattr(optimize, optimizer) + except AttributeError as e: + raise ValueError("%s is not a valid optimizer" % optimizer) from e + return optimizer + + +def _sum_finite(x): + """ + For a 1D array x, return a tuple containing the sum of the + finite values of x and the number of nonfinite values. + + This is a utility function used when evaluating the negative + loglikelihood for a distribution and an array of samples. + + Examples + -------- + >>> import numpy as np + >>> from scipy.stats._distn_infrastructure import _sum_finite + >>> tot, nbad = _sum_finite(np.array([-2, -np.inf, 5, 1])) + >>> tot + 4.0 + >>> nbad + 1 + """ + finite_x = np.isfinite(x) + bad_count = finite_x.size - np.count_nonzero(finite_x) + return np.sum(x[finite_x]), bad_count + + +# Frozen RV class +class rv_frozen: + + def __init__(self, dist, *args, **kwds): + self.args = args + self.kwds = kwds + + # create a new instance + self.dist = dist.__class__(**dist._updated_ctor_param()) + + shapes, _, _ = self.dist._parse_args(*args, **kwds) + self.a, self.b = self.dist._get_support(*shapes) + + @property + def random_state(self): + return self.dist._random_state + + @random_state.setter + def random_state(self, seed): + self.dist._random_state = check_random_state(seed) + + def cdf(self, x): + return self.dist.cdf(x, *self.args, **self.kwds) + + def logcdf(self, x): + return self.dist.logcdf(x, *self.args, **self.kwds) + + def ppf(self, q): + return self.dist.ppf(q, *self.args, **self.kwds) + + def isf(self, q): + return self.dist.isf(q, *self.args, **self.kwds) + + def rvs(self, size=None, random_state=None): + kwds = self.kwds.copy() + kwds.update({'size': size, 'random_state': random_state}) + return self.dist.rvs(*self.args, **kwds) + + def sf(self, x): + return self.dist.sf(x, *self.args, **self.kwds) + + def logsf(self, x): + return self.dist.logsf(x, *self.args, **self.kwds) + + def stats(self, moments='mv'): + kwds = self.kwds.copy() + kwds.update({'moments': moments}) + return self.dist.stats(*self.args, **kwds) + + def median(self): + return self.dist.median(*self.args, **self.kwds) + + def mean(self): + return self.dist.mean(*self.args, **self.kwds) + + def var(self): + return self.dist.var(*self.args, **self.kwds) + + def std(self): + return self.dist.std(*self.args, **self.kwds) + + def moment(self, order=None): + return self.dist.moment(order, *self.args, **self.kwds) + + def entropy(self): + return self.dist.entropy(*self.args, **self.kwds) + + def interval(self, confidence=None): + return self.dist.interval(confidence, *self.args, **self.kwds) + + def expect(self, func=None, lb=None, ub=None, conditional=False, **kwds): + # expect method only accepts shape parameters as positional args + # hence convert self.args, self.kwds, also loc/scale + # See the .expect method docstrings for the meaning of + # other parameters. + a, loc, scale = self.dist._parse_args(*self.args, **self.kwds) + if isinstance(self.dist, rv_discrete): + return self.dist.expect(func, a, loc, lb, ub, conditional, **kwds) + else: + return self.dist.expect(func, a, loc, scale, lb, ub, + conditional, **kwds) + + def support(self): + return self.dist.support(*self.args, **self.kwds) + + +class rv_discrete_frozen(rv_frozen): + + def pmf(self, k): + return self.dist.pmf(k, *self.args, **self.kwds) + + def logpmf(self, k): # No error + return self.dist.logpmf(k, *self.args, **self.kwds) + + +class rv_continuous_frozen(rv_frozen): + + def pdf(self, x): + return self.dist.pdf(x, *self.args, **self.kwds) + + def logpdf(self, x): + return self.dist.logpdf(x, *self.args, **self.kwds) + + +def argsreduce(cond, *args): + """Clean arguments to: + + 1. Ensure all arguments are iterable (arrays of dimension at least one + 2. If cond != True and size > 1, ravel(args[i]) where ravel(condition) is + True, in 1D. + + Return list of processed arguments. + + Examples + -------- + >>> import numpy as np + >>> from scipy.stats._distn_infrastructure import argsreduce + >>> rng = np.random.default_rng() + >>> A = rng.random((4, 5)) + >>> B = 2 + >>> C = rng.random((1, 5)) + >>> cond = np.ones(A.shape) + >>> [A1, B1, C1] = argsreduce(cond, A, B, C) + >>> A1.shape + (4, 5) + >>> B1.shape + (1,) + >>> C1.shape + (1, 5) + >>> cond[2,:] = 0 + >>> [A1, B1, C1] = argsreduce(cond, A, B, C) + >>> A1.shape + (15,) + >>> B1.shape + (1,) + >>> C1.shape + (15,) + + """ + # some distributions assume arguments are iterable. + newargs = np.atleast_1d(*args) + + # np.atleast_1d returns an array if only one argument, or a list of arrays + # if more than one argument. + if not isinstance(newargs, (list, tuple)): + newargs = (newargs,) + + if np.all(cond): + # broadcast arrays with cond + *newargs, cond = np.broadcast_arrays(*newargs, cond) + return [arg.ravel() for arg in newargs] + + s = cond.shape + # np.extract returns flattened arrays, which are not broadcastable together + # unless they are either the same size or size == 1. + return [(arg if np.size(arg) == 1 + else np.extract(cond, np.broadcast_to(arg, s))) + for arg in newargs] + + +parse_arg_template = """ +def _parse_args(self, %(shape_arg_str)s %(locscale_in)s): + return (%(shape_arg_str)s), %(locscale_out)s + +def _parse_args_rvs(self, %(shape_arg_str)s %(locscale_in)s, size=None): + return self._argcheck_rvs(%(shape_arg_str)s %(locscale_out)s, size=size) + +def _parse_args_stats(self, %(shape_arg_str)s %(locscale_in)s, moments='mv'): + return (%(shape_arg_str)s), %(locscale_out)s, moments +""" + + +class rv_generic: + """Class which encapsulates common functionality between rv_discrete + and rv_continuous. + + """ + + def __init__(self, seed=None): + super().__init__() + + # figure out if _stats signature has 'moments' keyword + sig = _getfullargspec(self._stats) + self._stats_has_moments = ((sig.varkw is not None) or + ('moments' in sig.args) or + ('moments' in sig.kwonlyargs)) + self._random_state = check_random_state(seed) + + @property + def random_state(self): + """Get or set the generator object for generating random variates. + + If `random_state` is None (or `np.random`), the + `numpy.random.RandomState` singleton is used. + If `random_state` is an int, a new ``RandomState`` instance is used, + seeded with `random_state`. + If `random_state` is already a ``Generator`` or ``RandomState`` + instance, that instance is used. + + """ + return self._random_state + + @random_state.setter + def random_state(self, seed): + self._random_state = check_random_state(seed) + + def __setstate__(self, state): + try: + self.__dict__.update(state) + # attaches the dynamically created methods on each instance. + # if a subclass overrides rv_generic.__setstate__, or implements + # it's own _attach_methods, then it must make sure that + # _attach_argparser_methods is called. + self._attach_methods() + except ValueError: + # reconstitute an old pickle scipy<1.6, that contains + # (_ctor_param, random_state) as state + self._ctor_param = state[0] + self._random_state = state[1] + self.__init__() + + def _attach_methods(self): + """Attaches dynamically created methods to the rv_* instance. + + This method must be overridden by subclasses, and must itself call + _attach_argparser_methods. This method is called in __init__ in + subclasses, and in __setstate__ + """ + raise NotImplementedError + + def _attach_argparser_methods(self): + """ + Generates the argument-parsing functions dynamically and attaches + them to the instance. + + Should be called from `_attach_methods`, typically in __init__ and + during unpickling (__setstate__) + """ + ns = {} + exec(self._parse_arg_template, ns) + # NB: attach to the instance, not class + for name in ['_parse_args', '_parse_args_stats', '_parse_args_rvs']: + setattr(self, name, types.MethodType(ns[name], self)) + + def _construct_argparser( + self, meths_to_inspect, locscale_in, locscale_out): + """Construct the parser string for the shape arguments. + + This method should be called in __init__ of a class for each + distribution. It creates the `_parse_arg_template` attribute that is + then used by `_attach_argparser_methods` to dynamically create and + attach the `_parse_args`, `_parse_args_stats`, `_parse_args_rvs` + methods to the instance. + + If self.shapes is a non-empty string, interprets it as a + comma-separated list of shape parameters. + + Otherwise inspects the call signatures of `meths_to_inspect` + and constructs the argument-parsing functions from these. + In this case also sets `shapes` and `numargs`. + """ + + if self.shapes: + # sanitize the user-supplied shapes + if not isinstance(self.shapes, str): + raise TypeError('shapes must be a string.') + + shapes = self.shapes.replace(',', ' ').split() + + for field in shapes: + if keyword.iskeyword(field): + raise SyntaxError('keywords cannot be used as shapes.') + if not re.match('^[_a-zA-Z][_a-zA-Z0-9]*$', field): + raise SyntaxError( + 'shapes must be valid python identifiers') + else: + # find out the call signatures (_pdf, _cdf etc), deduce shape + # arguments. Generic methods only have 'self, x', any further args + # are shapes. + shapes_list = [] + for meth in meths_to_inspect: + shapes_args = _getfullargspec(meth) # NB does not contain self + args = shapes_args.args[1:] # peel off 'x', too + + if args: + shapes_list.append(args) + + # *args or **kwargs are not allowed w/automatic shapes + if shapes_args.varargs is not None: + raise TypeError( + '*args are not allowed w/out explicit shapes') + if shapes_args.varkw is not None: + raise TypeError( + '**kwds are not allowed w/out explicit shapes') + if shapes_args.kwonlyargs: + raise TypeError( + 'kwonly args are not allowed w/out explicit shapes') + if shapes_args.defaults is not None: + raise TypeError('defaults are not allowed for shapes') + + if shapes_list: + shapes = shapes_list[0] + + # make sure the signatures are consistent + for item in shapes_list: + if item != shapes: + raise TypeError('Shape arguments are inconsistent.') + else: + shapes = [] + + # have the arguments, construct the method from template + shapes_str = ', '.join(shapes) + ', ' if shapes else '' # NB: not None + dct = dict(shape_arg_str=shapes_str, + locscale_in=locscale_in, + locscale_out=locscale_out, + ) + + # this string is used by _attach_argparser_methods + self._parse_arg_template = parse_arg_template % dct + + self.shapes = ', '.join(shapes) if shapes else None + if not hasattr(self, 'numargs'): + # allows more general subclassing with *args + self.numargs = len(shapes) + + def _construct_doc(self, docdict, shapes_vals=None): + """Construct the instance docstring with string substitutions.""" + tempdict = docdict.copy() + tempdict['name'] = self.name or 'distname' + tempdict['shapes'] = self.shapes or '' + + if shapes_vals is None: + shapes_vals = () + vals = ', '.join('%.3g' % val for val in shapes_vals) + tempdict['vals'] = vals + + tempdict['shapes_'] = self.shapes or '' + if self.shapes and self.numargs == 1: + tempdict['shapes_'] += ',' + + if self.shapes: + tempdict['set_vals_stmt'] = f'>>> {self.shapes} = {vals}' + else: + tempdict['set_vals_stmt'] = '' + + if self.shapes is None: + # remove shapes from call parameters if there are none + for item in ['default', 'before_notes']: + tempdict[item] = tempdict[item].replace( + "\n%(shapes)s : array_like\n shape parameters", "") + for i in range(2): + if self.shapes is None: + # necessary because we use %(shapes)s in two forms (w w/o ", ") + self.__doc__ = self.__doc__.replace("%(shapes)s, ", "") + try: + self.__doc__ = doccer.docformat(self.__doc__, tempdict) + except TypeError as e: + raise Exception("Unable to construct docstring for " + f"distribution \"{self.name}\": {repr(e)}") from e + + # correct for empty shapes + self.__doc__ = self.__doc__.replace('(, ', '(').replace(', )', ')') + + def _construct_default_doc(self, longname=None, + docdict=None, discrete='continuous'): + """Construct instance docstring from the default template.""" + if longname is None: + longname = 'A' + self.__doc__ = ''.join([f'{longname} {discrete} random variable.', + '\n\n%(before_notes)s\n', docheaders['notes'], + '\n%(example)s']) + self._construct_doc(docdict) + + def freeze(self, *args, **kwds): + """Freeze the distribution for the given arguments. + + Parameters + ---------- + arg1, arg2, arg3,... : array_like + The shape parameter(s) for the distribution. Should include all + the non-optional arguments, may include ``loc`` and ``scale``. + + Returns + ------- + rv_frozen : rv_frozen instance + The frozen distribution. + + """ + if isinstance(self, rv_continuous): + return rv_continuous_frozen(self, *args, **kwds) + else: + return rv_discrete_frozen(self, *args, **kwds) + + def __call__(self, *args, **kwds): + return self.freeze(*args, **kwds) + __call__.__doc__ = freeze.__doc__ + + # The actual calculation functions (no basic checking need be done) + # If these are defined, the others won't be looked at. + # Otherwise, the other set can be defined. + def _stats(self, *args, **kwds): + return None, None, None, None + + # Noncentral moments (also known as the moment about the origin). + # Expressed in LaTeX, munp would be $\mu'_{n}$, i.e. "mu-sub-n-prime". + # The primed mu is a widely used notation for the noncentral moment. + def _munp(self, n, *args): + # Silence floating point warnings from integration. + with np.errstate(all='ignore'): + vals = self.generic_moment(n, *args) + return vals + + def _argcheck_rvs(self, *args, **kwargs): + # Handle broadcasting and size validation of the rvs method. + # Subclasses should not have to override this method. + # The rule is that if `size` is not None, then `size` gives the + # shape of the result (integer values of `size` are treated as + # tuples with length 1; i.e. `size=3` is the same as `size=(3,)`.) + # + # `args` is expected to contain the shape parameters (if any), the + # location and the scale in a flat tuple (e.g. if there are two + # shape parameters `a` and `b`, `args` will be `(a, b, loc, scale)`). + # The only keyword argument expected is 'size'. + size = kwargs.get('size', None) + all_bcast = np.broadcast_arrays(*args) + + def squeeze_left(a): + while a.ndim > 0 and a.shape[0] == 1: + a = a[0] + return a + + # Eliminate trivial leading dimensions. In the convention + # used by numpy's random variate generators, trivial leading + # dimensions are effectively ignored. In other words, when `size` + # is given, trivial leading dimensions of the broadcast parameters + # in excess of the number of dimensions in size are ignored, e.g. + # >>> np.random.normal([[1, 3, 5]], [[[[0.01]]]], size=3) + # array([ 1.00104267, 3.00422496, 4.99799278]) + # If `size` is not given, the exact broadcast shape is preserved: + # >>> np.random.normal([[1, 3, 5]], [[[[0.01]]]]) + # array([[[[ 1.00862899, 3.00061431, 4.99867122]]]]) + # + all_bcast = [squeeze_left(a) for a in all_bcast] + bcast_shape = all_bcast[0].shape + bcast_ndim = all_bcast[0].ndim + + if size is None: + size_ = bcast_shape + else: + size_ = tuple(np.atleast_1d(size)) + + # Check compatibility of size_ with the broadcast shape of all + # the parameters. This check is intended to be consistent with + # how the numpy random variate generators (e.g. np.random.normal, + # np.random.beta) handle their arguments. The rule is that, if size + # is given, it determines the shape of the output. Broadcasting + # can't change the output size. + + # This is the standard broadcasting convention of extending the + # shape with fewer dimensions with enough dimensions of length 1 + # so that the two shapes have the same number of dimensions. + ndiff = bcast_ndim - len(size_) + if ndiff < 0: + bcast_shape = (1,)*(-ndiff) + bcast_shape + elif ndiff > 0: + size_ = (1,)*ndiff + size_ + + # This compatibility test is not standard. In "regular" broadcasting, + # two shapes are compatible if for each dimension, the lengths are the + # same or one of the lengths is 1. Here, the length of a dimension in + # size_ must not be less than the corresponding length in bcast_shape. + ok = all([bcdim == 1 or bcdim == szdim + for (bcdim, szdim) in zip(bcast_shape, size_)]) + if not ok: + raise ValueError("size does not match the broadcast shape of " + f"the parameters. {size}, {size_}, {bcast_shape}") + + param_bcast = all_bcast[:-2] + loc_bcast = all_bcast[-2] + scale_bcast = all_bcast[-1] + + return param_bcast, loc_bcast, scale_bcast, size_ + + # These are the methods you must define (standard form functions) + # NB: generic _pdf, _logpdf, _cdf are different for + # rv_continuous and rv_discrete hence are defined in there + def _argcheck(self, *args): + """Default check for correct values on args and keywords. + + Returns condition array of 1's where arguments are correct and + 0's where they are not. + + """ + cond = 1 + for arg in args: + cond = logical_and(cond, (asarray(arg) > 0)) + return cond + + def _get_support(self, *args, **kwargs): + """Return the support of the (unscaled, unshifted) distribution. + + *Must* be overridden by distributions which have support dependent + upon the shape parameters of the distribution. Any such override + *must not* set or change any of the class members, as these members + are shared amongst all instances of the distribution. + + Parameters + ---------- + arg1, arg2, ... : array_like + The shape parameter(s) for the distribution (see docstring of the + instance object for more information). + + Returns + ------- + a, b : numeric (float, or int or +/-np.inf) + end-points of the distribution's support for the specified + shape parameters. + """ + return self.a, self.b + + def _support_mask(self, x, *args): + a, b = self._get_support(*args) + with np.errstate(invalid='ignore'): + return (a <= x) & (x <= b) + + def _open_support_mask(self, x, *args): + a, b = self._get_support(*args) + with np.errstate(invalid='ignore'): + return (a < x) & (x < b) + + def _rvs(self, *args, size=None, random_state=None): + # This method must handle size being a tuple, and it must + # properly broadcast *args and size. size might be + # an empty tuple, which means a scalar random variate is to be + # generated. + + # Use basic inverse cdf algorithm for RV generation as default. + U = random_state.uniform(size=size) + Y = self._ppf(U, *args) + return Y + + def _logcdf(self, x, *args): + with np.errstate(divide='ignore'): + return log(self._cdf(x, *args)) + + def _sf(self, x, *args): + return 1.0-self._cdf(x, *args) + + def _logsf(self, x, *args): + with np.errstate(divide='ignore'): + return log(self._sf(x, *args)) + + def _ppf(self, q, *args): + return self._ppfvec(q, *args) + + def _isf(self, q, *args): + return self._ppf(1.0-q, *args) # use correct _ppf for subclasses + + # These are actually called, and should not be overwritten if you + # want to keep error checking. + def rvs(self, *args, **kwds): + """Random variates of given type. + + Parameters + ---------- + arg1, arg2, arg3,... : array_like + The shape parameter(s) for the distribution (see docstring of the + instance object for more information). + loc : array_like, optional + Location parameter (default=0). + scale : array_like, optional + Scale parameter (default=1). + size : int or tuple of ints, optional + Defining number of random variates (default is 1). + random_state : {None, int, `numpy.random.Generator`, + `numpy.random.RandomState`}, optional + + If `random_state` is None (or `np.random`), the + `numpy.random.RandomState` singleton is used. + If `random_state` is an int, a new ``RandomState`` instance is + used, seeded with `random_state`. + If `random_state` is already a ``Generator`` or ``RandomState`` + instance, that instance is used. + + Returns + ------- + rvs : ndarray or scalar + Random variates of given `size`. + + """ + discrete = kwds.pop('discrete', None) + rndm = kwds.pop('random_state', None) + args, loc, scale, size = self._parse_args_rvs(*args, **kwds) + cond = logical_and(self._argcheck(*args), (scale >= 0)) + if not np.all(cond): + message = ("Domain error in arguments. The `scale` parameter must " + "be positive for all distributions, and many " + "distributions have restrictions on shape parameters. " + f"Please see the `scipy.stats.{self.name}` " + "documentation for details.") + raise ValueError(message) + + if np.all(scale == 0): + return loc*ones(size, 'd') + + # extra gymnastics needed for a custom random_state + if rndm is not None: + random_state_saved = self._random_state + random_state = check_random_state(rndm) + else: + random_state = self._random_state + + vals = self._rvs(*args, size=size, random_state=random_state) + + vals = vals * scale + loc + + # do not forget to restore the _random_state + if rndm is not None: + self._random_state = random_state_saved + + # Cast to int if discrete + if discrete and not isinstance(self, rv_sample): + if size == (): + vals = int(vals) + else: + vals = vals.astype(np.int64) + + return vals + + def stats(self, *args, **kwds): + """Some statistics of the given RV. + + Parameters + ---------- + arg1, arg2, arg3,... : array_like + The shape parameter(s) for the distribution (see docstring of the + instance object for more information) + loc : array_like, optional + location parameter (default=0) + scale : array_like, optional (continuous RVs only) + scale parameter (default=1) + moments : str, optional + composed of letters ['mvsk'] defining which moments to compute: + 'm' = mean, + 'v' = variance, + 's' = (Fisher's) skew, + 'k' = (Fisher's) kurtosis. + (default is 'mv') + + Returns + ------- + stats : sequence + of requested moments. + + """ + args, loc, scale, moments = self._parse_args_stats(*args, **kwds) + # scale = 1 by construction for discrete RVs + loc, scale = map(asarray, (loc, scale)) + args = tuple(map(asarray, args)) + cond = self._argcheck(*args) & (scale > 0) & (loc == loc) + output = [] + default = np.full(shape(cond), fill_value=self.badvalue) + + # Use only entries that are valid in calculation + if np.any(cond): + goodargs = argsreduce(cond, *(args+(scale, loc))) + scale, loc, goodargs = goodargs[-2], goodargs[-1], goodargs[:-2] + + if self._stats_has_moments: + mu, mu2, g1, g2 = self._stats(*goodargs, + **{'moments': moments}) + else: + mu, mu2, g1, g2 = self._stats(*goodargs) + + if 'm' in moments: + if mu is None: + mu = self._munp(1, *goodargs) + out0 = default.copy() + place(out0, cond, mu * scale + loc) + output.append(out0) + + if 'v' in moments: + if mu2 is None: + mu2p = self._munp(2, *goodargs) + if mu is None: + mu = self._munp(1, *goodargs) + # if mean is inf then var is also inf + with np.errstate(invalid='ignore'): + mu2 = np.where(~np.isinf(mu), mu2p - mu**2, np.inf) + out0 = default.copy() + place(out0, cond, mu2 * scale * scale) + output.append(out0) + + if 's' in moments: + if g1 is None: + mu3p = self._munp(3, *goodargs) + if mu is None: + mu = self._munp(1, *goodargs) + if mu2 is None: + mu2p = self._munp(2, *goodargs) + with np.errstate(invalid='ignore'): + mu2 = mu2p - mu * mu + with np.errstate(invalid='ignore'): + mu3 = (-mu*mu - 3*mu2)*mu + mu3p + g1 = mu3 / np.power(mu2, 1.5) + out0 = default.copy() + place(out0, cond, g1) + output.append(out0) + + if 'k' in moments: + if g2 is None: + mu4p = self._munp(4, *goodargs) + if mu is None: + mu = self._munp(1, *goodargs) + if mu2 is None: + mu2p = self._munp(2, *goodargs) + with np.errstate(invalid='ignore'): + mu2 = mu2p - mu * mu + if g1 is None: + mu3 = None + else: + # (mu2**1.5) breaks down for nan and inf + mu3 = g1 * np.power(mu2, 1.5) + if mu3 is None: + mu3p = self._munp(3, *goodargs) + with np.errstate(invalid='ignore'): + mu3 = (-mu * mu - 3 * mu2) * mu + mu3p + with np.errstate(invalid='ignore'): + mu4 = ((-mu**2 - 6*mu2) * mu - 4*mu3)*mu + mu4p + g2 = mu4 / mu2**2.0 - 3.0 + out0 = default.copy() + place(out0, cond, g2) + output.append(out0) + else: # no valid args + output = [default.copy() for _ in moments] + + output = [out[()] for out in output] + if len(output) == 1: + return output[0] + else: + return tuple(output) + + def entropy(self, *args, **kwds): + """Differential entropy of the RV. + + Parameters + ---------- + arg1, arg2, arg3,... : array_like + The shape parameter(s) for the distribution (see docstring of the + instance object for more information). + loc : array_like, optional + Location parameter (default=0). + scale : array_like, optional (continuous distributions only). + Scale parameter (default=1). + + Notes + ----- + Entropy is defined base `e`: + + >>> import numpy as np + >>> from scipy.stats._distn_infrastructure import rv_discrete + >>> drv = rv_discrete(values=((0, 1), (0.5, 0.5))) + >>> np.allclose(drv.entropy(), np.log(2.0)) + True + + """ + args, loc, scale = self._parse_args(*args, **kwds) + # NB: for discrete distributions scale=1 by construction in _parse_args + loc, scale = map(asarray, (loc, scale)) + args = tuple(map(asarray, args)) + cond0 = self._argcheck(*args) & (scale > 0) & (loc == loc) + output = zeros(shape(cond0), 'd') + place(output, (1-cond0), self.badvalue) + goodargs = argsreduce(cond0, scale, *args) + goodscale = goodargs[0] + goodargs = goodargs[1:] + place(output, cond0, self.vecentropy(*goodargs) + log(goodscale)) + return output[()] + + def moment(self, order, *args, **kwds): + """non-central moment of distribution of specified order. + + Parameters + ---------- + order : int, order >= 1 + Order of moment. + arg1, arg2, arg3,... : float + The shape parameter(s) for the distribution (see docstring of the + instance object for more information). + loc : array_like, optional + location parameter (default=0) + scale : array_like, optional + scale parameter (default=1) + + """ + n = order + shapes, loc, scale = self._parse_args(*args, **kwds) + args = np.broadcast_arrays(*(*shapes, loc, scale)) + *shapes, loc, scale = args + + i0 = np.logical_and(self._argcheck(*shapes), scale > 0) + i1 = np.logical_and(i0, loc == 0) + i2 = np.logical_and(i0, loc != 0) + + args = argsreduce(i0, *shapes, loc, scale) + *shapes, loc, scale = args + + if (floor(n) != n): + raise ValueError("Moment must be an integer.") + if (n < 0): + raise ValueError("Moment must be positive.") + mu, mu2, g1, g2 = None, None, None, None + if (n > 0) and (n < 5): + if self._stats_has_moments: + mdict = {'moments': {1: 'm', 2: 'v', 3: 'vs', 4: 'mvsk'}[n]} + else: + mdict = {} + mu, mu2, g1, g2 = self._stats(*shapes, **mdict) + val = np.empty(loc.shape) # val needs to be indexed by loc + val[...] = _moment_from_stats(n, mu, mu2, g1, g2, self._munp, shapes) + + # Convert to transformed X = L + S*Y + # E[X^n] = E[(L+S*Y)^n] = L^n sum(comb(n, k)*(S/L)^k E[Y^k], k=0...n) + result = zeros(i0.shape) + place(result, ~i0, self.badvalue) + + if i1.any(): + res1 = scale[loc == 0]**n * val[loc == 0] + place(result, i1, res1) + + if i2.any(): + mom = [mu, mu2, g1, g2] + arrs = [i for i in mom if i is not None] + idx = [i for i in range(4) if mom[i] is not None] + if any(idx): + arrs = argsreduce(loc != 0, *arrs) + j = 0 + for i in idx: + mom[i] = arrs[j] + j += 1 + mu, mu2, g1, g2 = mom + args = argsreduce(loc != 0, *shapes, loc, scale, val) + *shapes, loc, scale, val = args + + res2 = zeros(loc.shape, dtype='d') + fac = scale / loc + for k in range(n): + valk = _moment_from_stats(k, mu, mu2, g1, g2, self._munp, + shapes) + res2 += comb(n, k, exact=True)*fac**k * valk + res2 += fac**n * val + res2 *= loc**n + place(result, i2, res2) + + return result[()] + + def median(self, *args, **kwds): + """Median of the distribution. + + Parameters + ---------- + arg1, arg2, arg3,... : array_like + The shape parameter(s) for the distribution (see docstring of the + instance object for more information) + loc : array_like, optional + Location parameter, Default is 0. + scale : array_like, optional + Scale parameter, Default is 1. + + Returns + ------- + median : float + The median of the distribution. + + See Also + -------- + rv_discrete.ppf + Inverse of the CDF + + """ + return self.ppf(0.5, *args, **kwds) + + def mean(self, *args, **kwds): + """Mean of the distribution. + + Parameters + ---------- + arg1, arg2, arg3,... : array_like + The shape parameter(s) for the distribution (see docstring of the + instance object for more information) + loc : array_like, optional + location parameter (default=0) + scale : array_like, optional + scale parameter (default=1) + + Returns + ------- + mean : float + the mean of the distribution + + """ + kwds['moments'] = 'm' + res = self.stats(*args, **kwds) + if isinstance(res, ndarray) and res.ndim == 0: + return res[()] + return res + + def var(self, *args, **kwds): + """Variance of the distribution. + + Parameters + ---------- + arg1, arg2, arg3,... : array_like + The shape parameter(s) for the distribution (see docstring of the + instance object for more information) + loc : array_like, optional + location parameter (default=0) + scale : array_like, optional + scale parameter (default=1) + + Returns + ------- + var : float + the variance of the distribution + + """ + kwds['moments'] = 'v' + res = self.stats(*args, **kwds) + if isinstance(res, ndarray) and res.ndim == 0: + return res[()] + return res + + def std(self, *args, **kwds): + """Standard deviation of the distribution. + + Parameters + ---------- + arg1, arg2, arg3,... : array_like + The shape parameter(s) for the distribution (see docstring of the + instance object for more information) + loc : array_like, optional + location parameter (default=0) + scale : array_like, optional + scale parameter (default=1) + + Returns + ------- + std : float + standard deviation of the distribution + + """ + kwds['moments'] = 'v' + res = sqrt(self.stats(*args, **kwds)) + return res + + def interval(self, confidence, *args, **kwds): + """Confidence interval with equal areas around the median. + + Parameters + ---------- + confidence : array_like of float + Probability that an rv will be drawn from the returned range. + Each value should be in the range [0, 1]. + arg1, arg2, ... : array_like + The shape parameter(s) for the distribution (see docstring of the + instance object for more information). + loc : array_like, optional + location parameter, Default is 0. + scale : array_like, optional + scale parameter, Default is 1. + + Returns + ------- + a, b : ndarray of float + end-points of range that contain ``100 * alpha %`` of the rv's + possible values. + + Notes + ----- + This is implemented as ``ppf([p_tail, 1-p_tail])``, where + ``ppf`` is the inverse cumulative distribution function and + ``p_tail = (1-confidence)/2``. Suppose ``[c, d]`` is the support of a + discrete distribution; then ``ppf([0, 1]) == (c-1, d)``. Therefore, + when ``confidence=1`` and the distribution is discrete, the left end + of the interval will be beyond the support of the distribution. + For discrete distributions, the interval will limit the probability + in each tail to be less than or equal to ``p_tail`` (usually + strictly less). + + """ + alpha = confidence + + alpha = asarray(alpha) + if np.any((alpha > 1) | (alpha < 0)): + raise ValueError("alpha must be between 0 and 1 inclusive") + q1 = (1.0-alpha)/2 + q2 = (1.0+alpha)/2 + a = self.ppf(q1, *args, **kwds) + b = self.ppf(q2, *args, **kwds) + return a, b + + def support(self, *args, **kwargs): + """Support of the distribution. + + Parameters + ---------- + arg1, arg2, ... : array_like + The shape parameter(s) for the distribution (see docstring of the + instance object for more information). + loc : array_like, optional + location parameter, Default is 0. + scale : array_like, optional + scale parameter, Default is 1. + + Returns + ------- + a, b : array_like + end-points of the distribution's support. + + """ + args, loc, scale = self._parse_args(*args, **kwargs) + arrs = np.broadcast_arrays(*args, loc, scale) + args, loc, scale = arrs[:-2], arrs[-2], arrs[-1] + cond = self._argcheck(*args) & (scale > 0) + _a, _b = self._get_support(*args) + if cond.all(): + return _a * scale + loc, _b * scale + loc + elif cond.ndim == 0: + return self.badvalue, self.badvalue + # promote bounds to at least float to fill in the badvalue + _a, _b = np.asarray(_a).astype('d'), np.asarray(_b).astype('d') + out_a, out_b = _a * scale + loc, _b * scale + loc + place(out_a, 1-cond, self.badvalue) + place(out_b, 1-cond, self.badvalue) + return out_a, out_b + + def nnlf(self, theta, x): + """Negative loglikelihood function. + Notes + ----- + This is ``-sum(log pdf(x, theta), axis=0)`` where `theta` are the + parameters (including loc and scale). + """ + loc, scale, args = self._unpack_loc_scale(theta) + if not self._argcheck(*args) or scale <= 0: + return inf + x = (asarray(x)-loc) / scale + n_log_scale = len(x) * log(scale) + if np.any(~self._support_mask(x, *args)): + return inf + return self._nnlf(x, *args) + n_log_scale + + def _nnlf(self, x, *args): + return -np.sum(self._logpxf(x, *args), axis=0) + + def _nlff_and_penalty(self, x, args, log_fitfun): + # negative log fit function + cond0 = ~self._support_mask(x, *args) + n_bad = np.count_nonzero(cond0, axis=0) + if n_bad > 0: + x = argsreduce(~cond0, x)[0] + logff = log_fitfun(x, *args) + finite_logff = np.isfinite(logff) + n_bad += np.sum(~finite_logff, axis=0) + if n_bad > 0: + penalty = n_bad * log(_XMAX) * 100 + return -np.sum(logff[finite_logff], axis=0) + penalty + return -np.sum(logff, axis=0) + + def _penalized_nnlf(self, theta, x): + """Penalized negative loglikelihood function. + i.e., - sum (log pdf(x, theta), axis=0) + penalty + where theta are the parameters (including loc and scale) + """ + loc, scale, args = self._unpack_loc_scale(theta) + if not self._argcheck(*args) or scale <= 0: + return inf + x = asarray((x-loc) / scale) + n_log_scale = len(x) * log(scale) + return self._nlff_and_penalty(x, args, self._logpxf) + n_log_scale + + def _penalized_nlpsf(self, theta, x): + """Penalized negative log product spacing function. + i.e., - sum (log (diff (cdf (x, theta))), axis=0) + penalty + where theta are the parameters (including loc and scale) + Follows reference [1] of scipy.stats.fit + """ + loc, scale, args = self._unpack_loc_scale(theta) + if not self._argcheck(*args) or scale <= 0: + return inf + x = (np.sort(x) - loc)/scale + + def log_psf(x, *args): + x, lj = np.unique(x, return_counts=True) # fast for sorted x + cdf_data = self._cdf(x, *args) if x.size else [] + if not (x.size and 1 - cdf_data[-1] <= 0): + cdf = np.concatenate(([0], cdf_data, [1])) + lj = np.concatenate((lj, [1])) + else: + cdf = np.concatenate(([0], cdf_data)) + # here we could use logcdf w/ logsumexp trick to take differences, + # but in the context of the method, it seems unlikely to matter + return lj * np.log(np.diff(cdf) / lj) + + return self._nlff_and_penalty(x, args, log_psf) + + +class _ShapeInfo: + def __init__(self, name, integrality=False, domain=(-np.inf, np.inf), + inclusive=(True, True)): + self.name = name + self.integrality = integrality + + domain = list(domain) + if np.isfinite(domain[0]) and not inclusive[0]: + domain[0] = np.nextafter(domain[0], np.inf) + if np.isfinite(domain[1]) and not inclusive[1]: + domain[1] = np.nextafter(domain[1], -np.inf) + self.domain = domain + + +def _get_fixed_fit_value(kwds, names): + """ + Given names such as `['f0', 'fa', 'fix_a']`, check that there is + at most one non-None value in `kwds` associaed with those names. + Return that value, or None if none of the names occur in `kwds`. + As a side effect, all occurrences of those names in `kwds` are + removed. + """ + vals = [(name, kwds.pop(name)) for name in names if name in kwds] + if len(vals) > 1: + repeated = [name for name, val in vals] + raise ValueError("fit method got multiple keyword arguments to " + "specify the same fixed parameter: " + + ', '.join(repeated)) + return vals[0][1] if vals else None + + +# continuous random variables: implement maybe later +# +# hf --- Hazard Function (PDF / SF) +# chf --- Cumulative hazard function (-log(SF)) +# psf --- Probability sparsity function (reciprocal of the pdf) in +# units of percent-point-function (as a function of q). +# Also, the derivative of the percent-point function. + + +class rv_continuous(rv_generic): + """A generic continuous random variable class meant for subclassing. + + `rv_continuous` is a base class to construct specific distribution classes + and instances for continuous random variables. It cannot be used + directly as a distribution. + + Parameters + ---------- + momtype : int, optional + The type of generic moment calculation to use: 0 for pdf, 1 (default) + for ppf. + a : float, optional + Lower bound of the support of the distribution, default is minus + infinity. + b : float, optional + Upper bound of the support of the distribution, default is plus + infinity. + xtol : float, optional + The tolerance for fixed point calculation for generic ppf. + badvalue : float, optional + The value in a result arrays that indicates a value that for which + some argument restriction is violated, default is np.nan. + name : str, optional + The name of the instance. This string is used to construct the default + example for distributions. + longname : str, optional + This string is used as part of the first line of the docstring returned + when a subclass has no docstring of its own. Note: `longname` exists + for backwards compatibility, do not use for new subclasses. + shapes : str, optional + The shape of the distribution. For example ``"m, n"`` for a + distribution that takes two integers as the two shape arguments for all + its methods. If not provided, shape parameters will be inferred from + the signature of the private methods, ``_pdf`` and ``_cdf`` of the + instance. + seed : {None, int, `numpy.random.Generator`, `numpy.random.RandomState`}, optional + If `seed` is None (or `np.random`), the `numpy.random.RandomState` + singleton is used. + If `seed` is an int, a new ``RandomState`` instance is used, + seeded with `seed`. + If `seed` is already a ``Generator`` or ``RandomState`` instance then + that instance is used. + + Methods + ------- + rvs + pdf + logpdf + cdf + logcdf + sf + logsf + ppf + isf + moment + stats + entropy + expect + median + mean + std + var + interval + __call__ + fit + fit_loc_scale + nnlf + support + + Notes + ----- + Public methods of an instance of a distribution class (e.g., ``pdf``, + ``cdf``) check their arguments and pass valid arguments to private, + computational methods (``_pdf``, ``_cdf``). For ``pdf(x)``, ``x`` is valid + if it is within the support of the distribution. + Whether a shape parameter is valid is decided by an ``_argcheck`` method + (which defaults to checking that its arguments are strictly positive.) + + **Subclassing** + + New random variables can be defined by subclassing the `rv_continuous` class + and re-defining at least the ``_pdf`` or the ``_cdf`` method (normalized + to location 0 and scale 1). + + If positive argument checking is not correct for your RV + then you will also need to re-define the ``_argcheck`` method. + + For most of the scipy.stats distributions, the support interval doesn't + depend on the shape parameters. ``x`` being in the support interval is + equivalent to ``self.a <= x <= self.b``. If either of the endpoints of + the support do depend on the shape parameters, then + i) the distribution must implement the ``_get_support`` method; and + ii) those dependent endpoints must be omitted from the distribution's + call to the ``rv_continuous`` initializer. + + Correct, but potentially slow defaults exist for the remaining + methods but for speed and/or accuracy you can over-ride:: + + _logpdf, _cdf, _logcdf, _ppf, _rvs, _isf, _sf, _logsf + + The default method ``_rvs`` relies on the inverse of the cdf, ``_ppf``, + applied to a uniform random variate. In order to generate random variates + efficiently, either the default ``_ppf`` needs to be overwritten (e.g. + if the inverse cdf can expressed in an explicit form) or a sampling + method needs to be implemented in a custom ``_rvs`` method. + + If possible, you should override ``_isf``, ``_sf`` or ``_logsf``. + The main reason would be to improve numerical accuracy: for example, + the survival function ``_sf`` is computed as ``1 - _cdf`` which can + result in loss of precision if ``_cdf(x)`` is close to one. + + **Methods that can be overwritten by subclasses** + :: + + _rvs + _pdf + _cdf + _sf + _ppf + _isf + _stats + _munp + _entropy + _argcheck + _get_support + + There are additional (internal and private) generic methods that can + be useful for cross-checking and for debugging, but might work in all + cases when directly called. + + A note on ``shapes``: subclasses need not specify them explicitly. In this + case, `shapes` will be automatically deduced from the signatures of the + overridden methods (`pdf`, `cdf` etc). + If, for some reason, you prefer to avoid relying on introspection, you can + specify ``shapes`` explicitly as an argument to the instance constructor. + + + **Frozen Distributions** + + Normally, you must provide shape parameters (and, optionally, location and + scale parameters to each call of a method of a distribution. + + Alternatively, the object may be called (as a function) to fix the shape, + location, and scale parameters returning a "frozen" continuous RV object: + + rv = generic(, loc=0, scale=1) + `rv_frozen` object with the same methods but holding the given shape, + location, and scale fixed + + **Statistics** + + Statistics are computed using numerical integration by default. + For speed you can redefine this using ``_stats``: + + - take shape parameters and return mu, mu2, g1, g2 + - If you can't compute one of these, return it as None + - Can also be defined with a keyword argument ``moments``, which is a + string composed of "m", "v", "s", and/or "k". + Only the components appearing in string should be computed and + returned in the order "m", "v", "s", or "k" with missing values + returned as None. + + Alternatively, you can override ``_munp``, which takes ``n`` and shape + parameters and returns the n-th non-central moment of the distribution. + + **Deepcopying / Pickling** + + If a distribution or frozen distribution is deepcopied (pickled/unpickled, + etc.), any underlying random number generator is deepcopied with it. An + implication is that if a distribution relies on the singleton RandomState + before copying, it will rely on a copy of that random state after copying, + and ``np.random.seed`` will no longer control the state. + + Examples + -------- + To create a new Gaussian distribution, we would do the following: + + >>> from scipy.stats import rv_continuous + >>> class gaussian_gen(rv_continuous): + ... "Gaussian distribution" + ... def _pdf(self, x): + ... return np.exp(-x**2 / 2.) / np.sqrt(2.0 * np.pi) + >>> gaussian = gaussian_gen(name='gaussian') + + ``scipy.stats`` distributions are *instances*, so here we subclass + `rv_continuous` and create an instance. With this, we now have + a fully functional distribution with all relevant methods automagically + generated by the framework. + + Note that above we defined a standard normal distribution, with zero mean + and unit variance. Shifting and scaling of the distribution can be done + by using ``loc`` and ``scale`` parameters: ``gaussian.pdf(x, loc, scale)`` + essentially computes ``y = (x - loc) / scale`` and + ``gaussian._pdf(y) / scale``. + + """ + + def __init__(self, momtype=1, a=None, b=None, xtol=1e-14, + badvalue=None, name=None, longname=None, + shapes=None, seed=None): + + super().__init__(seed) + + # save the ctor parameters, cf generic freeze + self._ctor_param = dict( + momtype=momtype, a=a, b=b, xtol=xtol, + badvalue=badvalue, name=name, longname=longname, + shapes=shapes, seed=seed) + + if badvalue is None: + badvalue = nan + if name is None: + name = 'Distribution' + self.badvalue = badvalue + self.name = name + self.a = a + self.b = b + if a is None: + self.a = -inf + if b is None: + self.b = inf + self.xtol = xtol + self.moment_type = momtype + self.shapes = shapes + + self._construct_argparser(meths_to_inspect=[self._pdf, self._cdf], + locscale_in='loc=0, scale=1', + locscale_out='loc, scale') + self._attach_methods() + + if longname is None: + if name[0] in ['aeiouAEIOU']: + hstr = "An " + else: + hstr = "A " + longname = hstr + name + + if sys.flags.optimize < 2: + # Skip adding docstrings if interpreter is run with -OO + if self.__doc__ is None: + self._construct_default_doc(longname=longname, + docdict=docdict, + discrete='continuous') + else: + dct = dict(distcont) + self._construct_doc(docdict, dct.get(self.name)) + + def __getstate__(self): + dct = self.__dict__.copy() + + # these methods will be remade in __setstate__ + # _random_state attribute is taken care of by rv_generic + attrs = ["_parse_args", "_parse_args_stats", "_parse_args_rvs", + "_cdfvec", "_ppfvec", "vecentropy", "generic_moment"] + [dct.pop(attr, None) for attr in attrs] + return dct + + def _attach_methods(self): + """ + Attaches dynamically created methods to the rv_continuous instance. + """ + # _attach_methods is responsible for calling _attach_argparser_methods + self._attach_argparser_methods() + + # nin correction + self._ppfvec = vectorize(self._ppf_single, otypes='d') + self._ppfvec.nin = self.numargs + 1 + self.vecentropy = vectorize(self._entropy, otypes='d') + self._cdfvec = vectorize(self._cdf_single, otypes='d') + self._cdfvec.nin = self.numargs + 1 + + if self.moment_type == 0: + self.generic_moment = vectorize(self._mom0_sc, otypes='d') + else: + self.generic_moment = vectorize(self._mom1_sc, otypes='d') + # Because of the *args argument of _mom0_sc, vectorize cannot count the + # number of arguments correctly. + self.generic_moment.nin = self.numargs + 1 + + def _updated_ctor_param(self): + """Return the current version of _ctor_param, possibly updated by user. + + Used by freezing. + Keep this in sync with the signature of __init__. + """ + dct = self._ctor_param.copy() + dct['a'] = self.a + dct['b'] = self.b + dct['xtol'] = self.xtol + dct['badvalue'] = self.badvalue + dct['name'] = self.name + dct['shapes'] = self.shapes + return dct + + def _ppf_to_solve(self, x, q, *args): + return self.cdf(*(x, )+args)-q + + def _ppf_single(self, q, *args): + factor = 10. + left, right = self._get_support(*args) + + if np.isinf(left): + left = min(-factor, right) + while self._ppf_to_solve(left, q, *args) > 0.: + left, right = left * factor, left + # left is now such that cdf(left) <= q + # if right has changed, then cdf(right) > q + + if np.isinf(right): + right = max(factor, left) + while self._ppf_to_solve(right, q, *args) < 0.: + left, right = right, right * factor + # right is now such that cdf(right) >= q + + return optimize.brentq(self._ppf_to_solve, + left, right, args=(q,)+args, xtol=self.xtol) + + # moment from definition + def _mom_integ0(self, x, m, *args): + return x**m * self.pdf(x, *args) + + def _mom0_sc(self, m, *args): + _a, _b = self._get_support(*args) + return integrate.quad(self._mom_integ0, _a, _b, + args=(m,)+args)[0] + + # moment calculated using ppf + def _mom_integ1(self, q, m, *args): + return (self.ppf(q, *args))**m + + def _mom1_sc(self, m, *args): + return integrate.quad(self._mom_integ1, 0, 1, args=(m,)+args)[0] + + def _pdf(self, x, *args): + return _derivative(self._cdf, x, dx=1e-5, args=args, order=5) + + # Could also define any of these + def _logpdf(self, x, *args): + p = self._pdf(x, *args) + with np.errstate(divide='ignore'): + return log(p) + + def _logpxf(self, x, *args): + # continuous distributions have PDF, discrete have PMF, but sometimes + # the distinction doesn't matter. This lets us use `_logpxf` for both + # discrete and continuous distributions. + return self._logpdf(x, *args) + + def _cdf_single(self, x, *args): + _a, _b = self._get_support(*args) + return integrate.quad(self._pdf, _a, x, args=args)[0] + + def _cdf(self, x, *args): + return self._cdfvec(x, *args) + + # generic _argcheck, _logcdf, _sf, _logsf, _ppf, _isf, _rvs are defined + # in rv_generic + + def pdf(self, x, *args, **kwds): + """Probability density function at x of the given RV. + + Parameters + ---------- + x : array_like + quantiles + arg1, arg2, arg3,... : array_like + The shape parameter(s) for the distribution (see docstring of the + instance object for more information) + loc : array_like, optional + location parameter (default=0) + scale : array_like, optional + scale parameter (default=1) + + Returns + ------- + pdf : ndarray + Probability density function evaluated at x + + """ + args, loc, scale = self._parse_args(*args, **kwds) + x, loc, scale = map(asarray, (x, loc, scale)) + args = tuple(map(asarray, args)) + dtyp = np.promote_types(x.dtype, np.float64) + x = np.asarray((x - loc)/scale, dtype=dtyp) + cond0 = self._argcheck(*args) & (scale > 0) + cond1 = self._support_mask(x, *args) & (scale > 0) + cond = cond0 & cond1 + output = zeros(shape(cond), dtyp) + putmask(output, (1-cond0)+np.isnan(x), self.badvalue) + if np.any(cond): + goodargs = argsreduce(cond, *((x,)+args+(scale,))) + scale, goodargs = goodargs[-1], goodargs[:-1] + place(output, cond, self._pdf(*goodargs) / scale) + if output.ndim == 0: + return output[()] + return output + + def logpdf(self, x, *args, **kwds): + """Log of the probability density function at x of the given RV. + + This uses a more numerically accurate calculation if available. + + Parameters + ---------- + x : array_like + quantiles + arg1, arg2, arg3,... : array_like + The shape parameter(s) for the distribution (see docstring of the + instance object for more information) + loc : array_like, optional + location parameter (default=0) + scale : array_like, optional + scale parameter (default=1) + + Returns + ------- + logpdf : array_like + Log of the probability density function evaluated at x + + """ + args, loc, scale = self._parse_args(*args, **kwds) + x, loc, scale = map(asarray, (x, loc, scale)) + args = tuple(map(asarray, args)) + dtyp = np.promote_types(x.dtype, np.float64) + x = np.asarray((x - loc)/scale, dtype=dtyp) + cond0 = self._argcheck(*args) & (scale > 0) + cond1 = self._support_mask(x, *args) & (scale > 0) + cond = cond0 & cond1 + output = empty(shape(cond), dtyp) + output.fill(-inf) + putmask(output, (1-cond0)+np.isnan(x), self.badvalue) + if np.any(cond): + goodargs = argsreduce(cond, *((x,)+args+(scale,))) + scale, goodargs = goodargs[-1], goodargs[:-1] + place(output, cond, self._logpdf(*goodargs) - log(scale)) + if output.ndim == 0: + return output[()] + return output + + def cdf(self, x, *args, **kwds): + """ + Cumulative distribution function of the given RV. + + Parameters + ---------- + x : array_like + quantiles + arg1, arg2, arg3,... : array_like + The shape parameter(s) for the distribution (see docstring of the + instance object for more information) + loc : array_like, optional + location parameter (default=0) + scale : array_like, optional + scale parameter (default=1) + + Returns + ------- + cdf : ndarray + Cumulative distribution function evaluated at `x` + + """ + args, loc, scale = self._parse_args(*args, **kwds) + x, loc, scale = map(asarray, (x, loc, scale)) + args = tuple(map(asarray, args)) + _a, _b = self._get_support(*args) + dtyp = np.promote_types(x.dtype, np.float64) + x = np.asarray((x - loc)/scale, dtype=dtyp) + cond0 = self._argcheck(*args) & (scale > 0) + cond1 = self._open_support_mask(x, *args) & (scale > 0) + cond2 = (x >= np.asarray(_b)) & cond0 + cond = cond0 & cond1 + output = zeros(shape(cond), dtyp) + place(output, (1-cond0)+np.isnan(x), self.badvalue) + place(output, cond2, 1.0) + if np.any(cond): # call only if at least 1 entry + goodargs = argsreduce(cond, *((x,)+args)) + place(output, cond, self._cdf(*goodargs)) + if output.ndim == 0: + return output[()] + return output + + def logcdf(self, x, *args, **kwds): + """Log of the cumulative distribution function at x of the given RV. + + Parameters + ---------- + x : array_like + quantiles + arg1, arg2, arg3,... : array_like + The shape parameter(s) for the distribution (see docstring of the + instance object for more information) + loc : array_like, optional + location parameter (default=0) + scale : array_like, optional + scale parameter (default=1) + + Returns + ------- + logcdf : array_like + Log of the cumulative distribution function evaluated at x + + """ + args, loc, scale = self._parse_args(*args, **kwds) + x, loc, scale = map(asarray, (x, loc, scale)) + args = tuple(map(asarray, args)) + _a, _b = self._get_support(*args) + dtyp = np.promote_types(x.dtype, np.float64) + x = np.asarray((x - loc)/scale, dtype=dtyp) + cond0 = self._argcheck(*args) & (scale > 0) + cond1 = self._open_support_mask(x, *args) & (scale > 0) + cond2 = (x >= _b) & cond0 + cond = cond0 & cond1 + output = empty(shape(cond), dtyp) + output.fill(-inf) + place(output, (1-cond0)*(cond1 == cond1)+np.isnan(x), self.badvalue) + place(output, cond2, 0.0) + if np.any(cond): # call only if at least 1 entry + goodargs = argsreduce(cond, *((x,)+args)) + place(output, cond, self._logcdf(*goodargs)) + if output.ndim == 0: + return output[()] + return output + + def sf(self, x, *args, **kwds): + """Survival function (1 - `cdf`) at x of the given RV. + + Parameters + ---------- + x : array_like + quantiles + arg1, arg2, arg3,... : array_like + The shape parameter(s) for the distribution (see docstring of the + instance object for more information) + loc : array_like, optional + location parameter (default=0) + scale : array_like, optional + scale parameter (default=1) + + Returns + ------- + sf : array_like + Survival function evaluated at x + + """ + args, loc, scale = self._parse_args(*args, **kwds) + x, loc, scale = map(asarray, (x, loc, scale)) + args = tuple(map(asarray, args)) + _a, _b = self._get_support(*args) + dtyp = np.promote_types(x.dtype, np.float64) + x = np.asarray((x - loc)/scale, dtype=dtyp) + cond0 = self._argcheck(*args) & (scale > 0) + cond1 = self._open_support_mask(x, *args) & (scale > 0) + cond2 = cond0 & (x <= _a) + cond = cond0 & cond1 + output = zeros(shape(cond), dtyp) + place(output, (1-cond0)+np.isnan(x), self.badvalue) + place(output, cond2, 1.0) + if np.any(cond): + goodargs = argsreduce(cond, *((x,)+args)) + place(output, cond, self._sf(*goodargs)) + if output.ndim == 0: + return output[()] + return output + + def logsf(self, x, *args, **kwds): + """Log of the survival function of the given RV. + + Returns the log of the "survival function," defined as (1 - `cdf`), + evaluated at `x`. + + Parameters + ---------- + x : array_like + quantiles + arg1, arg2, arg3,... : array_like + The shape parameter(s) for the distribution (see docstring of the + instance object for more information) + loc : array_like, optional + location parameter (default=0) + scale : array_like, optional + scale parameter (default=1) + + Returns + ------- + logsf : ndarray + Log of the survival function evaluated at `x`. + + """ + args, loc, scale = self._parse_args(*args, **kwds) + x, loc, scale = map(asarray, (x, loc, scale)) + args = tuple(map(asarray, args)) + _a, _b = self._get_support(*args) + dtyp = np.promote_types(x.dtype, np.float64) + x = np.asarray((x - loc)/scale, dtype=dtyp) + cond0 = self._argcheck(*args) & (scale > 0) + cond1 = self._open_support_mask(x, *args) & (scale > 0) + cond2 = cond0 & (x <= _a) + cond = cond0 & cond1 + output = empty(shape(cond), dtyp) + output.fill(-inf) + place(output, (1-cond0)+np.isnan(x), self.badvalue) + place(output, cond2, 0.0) + if np.any(cond): + goodargs = argsreduce(cond, *((x,)+args)) + place(output, cond, self._logsf(*goodargs)) + if output.ndim == 0: + return output[()] + return output + + def ppf(self, q, *args, **kwds): + """Percent point function (inverse of `cdf`) at q of the given RV. + + Parameters + ---------- + q : array_like + lower tail probability + arg1, arg2, arg3,... : array_like + The shape parameter(s) for the distribution (see docstring of the + instance object for more information) + loc : array_like, optional + location parameter (default=0) + scale : array_like, optional + scale parameter (default=1) + + Returns + ------- + x : array_like + quantile corresponding to the lower tail probability q. + + """ + args, loc, scale = self._parse_args(*args, **kwds) + q, loc, scale = map(asarray, (q, loc, scale)) + args = tuple(map(asarray, args)) + _a, _b = self._get_support(*args) + cond0 = self._argcheck(*args) & (scale > 0) & (loc == loc) + cond1 = (0 < q) & (q < 1) + cond2 = cond0 & (q == 0) + cond3 = cond0 & (q == 1) + cond = cond0 & cond1 + output = np.full(shape(cond), fill_value=self.badvalue) + + lower_bound = _a * scale + loc + upper_bound = _b * scale + loc + place(output, cond2, argsreduce(cond2, lower_bound)[0]) + place(output, cond3, argsreduce(cond3, upper_bound)[0]) + + if np.any(cond): # call only if at least 1 entry + goodargs = argsreduce(cond, *((q,)+args+(scale, loc))) + scale, loc, goodargs = goodargs[-2], goodargs[-1], goodargs[:-2] + place(output, cond, self._ppf(*goodargs) * scale + loc) + if output.ndim == 0: + return output[()] + return output + + def isf(self, q, *args, **kwds): + """Inverse survival function (inverse of `sf`) at q of the given RV. + + Parameters + ---------- + q : array_like + upper tail probability + arg1, arg2, arg3,... : array_like + The shape parameter(s) for the distribution (see docstring of the + instance object for more information) + loc : array_like, optional + location parameter (default=0) + scale : array_like, optional + scale parameter (default=1) + + Returns + ------- + x : ndarray or scalar + Quantile corresponding to the upper tail probability q. + + """ + args, loc, scale = self._parse_args(*args, **kwds) + q, loc, scale = map(asarray, (q, loc, scale)) + args = tuple(map(asarray, args)) + _a, _b = self._get_support(*args) + cond0 = self._argcheck(*args) & (scale > 0) & (loc == loc) + cond1 = (0 < q) & (q < 1) + cond2 = cond0 & (q == 1) + cond3 = cond0 & (q == 0) + cond = cond0 & cond1 + output = np.full(shape(cond), fill_value=self.badvalue) + + lower_bound = _a * scale + loc + upper_bound = _b * scale + loc + place(output, cond2, argsreduce(cond2, lower_bound)[0]) + place(output, cond3, argsreduce(cond3, upper_bound)[0]) + + if np.any(cond): + goodargs = argsreduce(cond, *((q,)+args+(scale, loc))) + scale, loc, goodargs = goodargs[-2], goodargs[-1], goodargs[:-2] + place(output, cond, self._isf(*goodargs) * scale + loc) + if output.ndim == 0: + return output[()] + return output + + def _unpack_loc_scale(self, theta): + try: + loc = theta[-2] + scale = theta[-1] + args = tuple(theta[:-2]) + except IndexError as e: + raise ValueError("Not enough input arguments.") from e + return loc, scale, args + + def _nnlf_and_penalty(self, x, args): + """ + Compute the penalized negative log-likelihood for the + "standardized" data (i.e. already shifted by loc and + scaled by scale) for the shape parameters in `args`. + + `x` can be a 1D numpy array or a CensoredData instance. + """ + if isinstance(x, CensoredData): + # Filter out the data that is not in the support. + xs = x._supported(*self._get_support(*args)) + n_bad = len(x) - len(xs) + i1, i2 = xs._interval.T + terms = [ + # logpdf of the noncensored data. + self._logpdf(xs._uncensored, *args), + # logcdf of the left-censored data. + self._logcdf(xs._left, *args), + # logsf of the right-censored data. + self._logsf(xs._right, *args), + # log of probability of the interval-censored data. + np.log(self._delta_cdf(i1, i2, *args)), + ] + else: + cond0 = ~self._support_mask(x, *args) + n_bad = np.count_nonzero(cond0) + if n_bad > 0: + x = argsreduce(~cond0, x)[0] + terms = [self._logpdf(x, *args)] + + totals, bad_counts = zip(*[_sum_finite(term) for term in terms]) + total = sum(totals) + n_bad += sum(bad_counts) + + return -total + n_bad * _LOGXMAX * 100 + + def _penalized_nnlf(self, theta, x): + """Penalized negative loglikelihood function. + + i.e., - sum (log pdf(x, theta), axis=0) + penalty + where theta are the parameters (including loc and scale) + """ + loc, scale, args = self._unpack_loc_scale(theta) + if not self._argcheck(*args) or scale <= 0: + return inf + if isinstance(x, CensoredData): + x = (x - loc) / scale + n_log_scale = (len(x) - x.num_censored()) * log(scale) + else: + x = (x - loc) / scale + n_log_scale = len(x) * log(scale) + + return self._nnlf_and_penalty(x, args) + n_log_scale + + def _fitstart(self, data, args=None): + """Starting point for fit (shape arguments + loc + scale).""" + if args is None: + args = (1.0,)*self.numargs + loc, scale = self._fit_loc_scale_support(data, *args) + return args + (loc, scale) + + def _reduce_func(self, args, kwds, data=None): + """ + Return the (possibly reduced) function to optimize in order to find MLE + estimates for the .fit method. + """ + # Convert fixed shape parameters to the standard numeric form: e.g. for + # stats.beta, shapes='a, b'. To fix `a`, the caller can give a value + # for `f0`, `fa` or 'fix_a'. The following converts the latter two + # into the first (numeric) form. + shapes = [] + if self.shapes: + shapes = self.shapes.replace(',', ' ').split() + for j, s in enumerate(shapes): + key = 'f' + str(j) + names = [key, 'f' + s, 'fix_' + s] + val = _get_fixed_fit_value(kwds, names) + if val is not None: + kwds[key] = val + + args = list(args) + Nargs = len(args) + fixedn = [] + names = ['f%d' % n for n in range(Nargs - 2)] + ['floc', 'fscale'] + x0 = [] + for n, key in enumerate(names): + if key in kwds: + fixedn.append(n) + args[n] = kwds.pop(key) + else: + x0.append(args[n]) + + methods = {"mle", "mm"} + method = kwds.pop('method', "mle").lower() + if method == "mm": + n_params = len(shapes) + 2 - len(fixedn) + exponents = (np.arange(1, n_params+1))[:, np.newaxis] + data_moments = np.sum(data[None, :]**exponents/len(data), axis=1) + + def objective(theta, x): + return self._moment_error(theta, x, data_moments) + + elif method == "mle": + objective = self._penalized_nnlf + else: + raise ValueError(f"Method '{method}' not available; " + f"must be one of {methods}") + + if len(fixedn) == 0: + func = objective + restore = None + else: + if len(fixedn) == Nargs: + raise ValueError( + "All parameters fixed. There is nothing to optimize.") + + def restore(args, theta): + # Replace with theta for all numbers not in fixedn + # This allows the non-fixed values to vary, but + # we still call self.nnlf with all parameters. + i = 0 + for n in range(Nargs): + if n not in fixedn: + args[n] = theta[i] + i += 1 + return args + + def func(theta, x): + newtheta = restore(args[:], theta) + return objective(newtheta, x) + + return x0, func, restore, args + + def _moment_error(self, theta, x, data_moments): + loc, scale, args = self._unpack_loc_scale(theta) + if not self._argcheck(*args) or scale <= 0: + return inf + + dist_moments = np.array([self.moment(i+1, *args, loc=loc, scale=scale) + for i in range(len(data_moments))]) + if np.any(np.isnan(dist_moments)): + raise ValueError("Method of moments encountered a non-finite " + "distribution moment and cannot continue. " + "Consider trying method='MLE'.") + + return (((data_moments - dist_moments) / + np.maximum(np.abs(data_moments), 1e-8))**2).sum() + + def fit(self, data, *args, **kwds): + r""" + Return estimates of shape (if applicable), location, and scale + parameters from data. The default estimation method is Maximum + Likelihood Estimation (MLE), but Method of Moments (MM) + is also available. + + Starting estimates for the fit are given by input arguments; + for any arguments not provided with starting estimates, + ``self._fitstart(data)`` is called to generate such. + + One can hold some parameters fixed to specific values by passing in + keyword arguments ``f0``, ``f1``, ..., ``fn`` (for shape parameters) + and ``floc`` and ``fscale`` (for location and scale parameters, + respectively). + + Parameters + ---------- + data : array_like or `CensoredData` instance + Data to use in estimating the distribution parameters. + arg1, arg2, arg3,... : floats, optional + Starting value(s) for any shape-characterizing arguments (those not + provided will be determined by a call to ``_fitstart(data)``). + No default value. + **kwds : floats, optional + - `loc`: initial guess of the distribution's location parameter. + - `scale`: initial guess of the distribution's scale parameter. + + Special keyword arguments are recognized as holding certain + parameters fixed: + + - f0...fn : hold respective shape parameters fixed. + Alternatively, shape parameters to fix can be specified by name. + For example, if ``self.shapes == "a, b"``, ``fa`` and ``fix_a`` + are equivalent to ``f0``, and ``fb`` and ``fix_b`` are + equivalent to ``f1``. + + - floc : hold location parameter fixed to specified value. + + - fscale : hold scale parameter fixed to specified value. + + - optimizer : The optimizer to use. The optimizer must take + ``func`` and starting position as the first two arguments, + plus ``args`` (for extra arguments to pass to the + function to be optimized) and ``disp``. + The ``fit`` method calls the optimizer with ``disp=0`` to suppress output. + The optimizer must return the estimated parameters. + + - method : The method to use. The default is "MLE" (Maximum + Likelihood Estimate); "MM" (Method of Moments) + is also available. + + Raises + ------ + TypeError, ValueError + If an input is invalid + `~scipy.stats.FitError` + If fitting fails or the fit produced would be invalid + + Returns + ------- + parameter_tuple : tuple of floats + Estimates for any shape parameters (if applicable), followed by + those for location and scale. For most random variables, shape + statistics will be returned, but there are exceptions (e.g. + ``norm``). + + Notes + ----- + With ``method="MLE"`` (default), the fit is computed by minimizing + the negative log-likelihood function. A large, finite penalty + (rather than infinite negative log-likelihood) is applied for + observations beyond the support of the distribution. + + With ``method="MM"``, the fit is computed by minimizing the L2 norm + of the relative errors between the first *k* raw (about zero) data + moments and the corresponding distribution moments, where *k* is the + number of non-fixed parameters. + More precisely, the objective function is:: + + (((data_moments - dist_moments) + / np.maximum(np.abs(data_moments), 1e-8))**2).sum() + + where the constant ``1e-8`` avoids division by zero in case of + vanishing data moments. Typically, this error norm can be reduced to + zero. + Note that the standard method of moments can produce parameters for + which some data are outside the support of the fitted distribution; + this implementation does nothing to prevent this. + + For either method, + the returned answer is not guaranteed to be globally optimal; it + may only be locally optimal, or the optimization may fail altogether. + If the data contain any of ``np.nan``, ``np.inf``, or ``-np.inf``, + the `fit` method will raise a ``RuntimeError``. + + When passing a ``CensoredData`` instance to ``data``, the log-likelihood + function is defined as: + + .. math:: + + l(\pmb{\theta}; k) & = \sum + \log(f(k_u; \pmb{\theta})) + + \sum + \log(F(k_l; \pmb{\theta})) \\ + & + \sum + \log(1 - F(k_r; \pmb{\theta})) \\ + & + \sum + \log(F(k_{\text{high}, i}; \pmb{\theta}) + - F(k_{\text{low}, i}; \pmb{\theta})) + + where :math:`f` and :math:`F` are the pdf and cdf, respectively, of the + function being fitted, :math:`\pmb{\theta}` is the parameter vector, + :math:`u` are the indices of uncensored observations, + :math:`l` are the indices of left-censored observations, + :math:`r` are the indices of right-censored observations, + subscripts "low"/"high" denote endpoints of interval-censored observations, and + :math:`i` are the indices of interval-censored observations. + + Examples + -------- + + Generate some data to fit: draw random variates from the `beta` + distribution + + >>> import numpy as np + >>> from scipy.stats import beta + >>> a, b = 1., 2. + >>> rng = np.random.default_rng(172786373191770012695001057628748821561) + >>> x = beta.rvs(a, b, size=1000, random_state=rng) + + Now we can fit all four parameters (``a``, ``b``, ``loc`` and + ``scale``): + + >>> a1, b1, loc1, scale1 = beta.fit(x) + >>> a1, b1, loc1, scale1 + (1.0198945204435628, 1.9484708982737828, 4.372241314917588e-05, 0.9979078845964814) + + The fit can be done also using a custom optimizer: + + >>> from scipy.optimize import minimize + >>> def custom_optimizer(func, x0, args=(), disp=0): + ... res = minimize(func, x0, args, method="slsqp", options={"disp": disp}) + ... if res.success: + ... return res.x + ... raise RuntimeError('optimization routine failed') + >>> a1, b1, loc1, scale1 = beta.fit(x, method="MLE", optimizer=custom_optimizer) + >>> a1, b1, loc1, scale1 + (1.0198821087258905, 1.948484145914738, 4.3705304486881485e-05, 0.9979104663953395) + + We can also use some prior knowledge about the dataset: let's keep + ``loc`` and ``scale`` fixed: + + >>> a1, b1, loc1, scale1 = beta.fit(x, floc=0, fscale=1) + >>> loc1, scale1 + (0, 1) + + We can also keep shape parameters fixed by using ``f``-keywords. To + keep the zero-th shape parameter ``a`` equal 1, use ``f0=1`` or, + equivalently, ``fa=1``: + + >>> a1, b1, loc1, scale1 = beta.fit(x, fa=1, floc=0, fscale=1) + >>> a1 + 1 + + Not all distributions return estimates for the shape parameters. + ``norm`` for example just returns estimates for location and scale: + + >>> from scipy.stats import norm + >>> x = norm.rvs(a, b, size=1000, random_state=123) + >>> loc1, scale1 = norm.fit(x) + >>> loc1, scale1 + (0.92087172783841631, 2.0015750750324668) + """ # noqa: E501 + method = kwds.get('method', "mle").lower() + + censored = isinstance(data, CensoredData) + if censored: + if method != 'mle': + raise ValueError('For censored data, the method must' + ' be "MLE".') + if data.num_censored() == 0: + # There are no censored values in data, so replace the + # CensoredData instance with a regular array. + data = data._uncensored + censored = False + + Narg = len(args) + if Narg > self.numargs: + raise TypeError("Too many input arguments.") + + # Check the finiteness of data only if data is not an instance of + # CensoredData. The arrays in a CensoredData instance have already + # been validated. + if not censored: + # Note: `ravel()` is called for backwards compatibility. + data = np.asarray(data).ravel() + if not np.isfinite(data).all(): + raise ValueError("The data contains non-finite values.") + + start = [None]*2 + if (Narg < self.numargs) or not ('loc' in kwds and + 'scale' in kwds): + # get distribution specific starting locations + start = self._fitstart(data) + args += start[Narg:-2] + loc = kwds.pop('loc', start[-2]) + scale = kwds.pop('scale', start[-1]) + args += (loc, scale) + x0, func, restore, args = self._reduce_func(args, kwds, data=data) + optimizer = kwds.pop('optimizer', optimize.fmin) + # convert string to function in scipy.optimize + optimizer = _fit_determine_optimizer(optimizer) + # by now kwds must be empty, since everybody took what they needed + if kwds: + raise TypeError("Unknown arguments: %s." % kwds) + + # In some cases, method of moments can be done with fsolve/root + # instead of an optimizer, but sometimes no solution exists, + # especially when the user fixes parameters. Minimizing the sum + # of squares of the error generalizes to these cases. + vals = optimizer(func, x0, args=(data,), disp=0) + obj = func(vals, data) + + if restore is not None: + vals = restore(args, vals) + vals = tuple(vals) + + loc, scale, shapes = self._unpack_loc_scale(vals) + if not (np.all(self._argcheck(*shapes)) and scale > 0): + raise FitError("Optimization converged to parameters that are " + "outside the range allowed by the distribution.") + + if method == 'mm': + if not np.isfinite(obj): + raise FitError("Optimization failed: either a data moment " + "or fitted distribution moment is " + "non-finite.") + + return vals + + def _fit_loc_scale_support(self, data, *args): + """Estimate loc and scale parameters from data accounting for support. + + Parameters + ---------- + data : array_like + Data to fit. + arg1, arg2, arg3,... : array_like + The shape parameter(s) for the distribution (see docstring of the + instance object for more information). + + Returns + ------- + Lhat : float + Estimated location parameter for the data. + Shat : float + Estimated scale parameter for the data. + + """ + if isinstance(data, CensoredData): + # For this estimate, "uncensor" the data by taking the + # given endpoints as the data for the left- or right-censored + # data, and the mean for the interval-censored data. + data = data._uncensor() + else: + data = np.asarray(data) + + # Estimate location and scale according to the method of moments. + loc_hat, scale_hat = self.fit_loc_scale(data, *args) + + # Compute the support according to the shape parameters. + self._argcheck(*args) + _a, _b = self._get_support(*args) + a, b = _a, _b + support_width = b - a + + # If the support is empty then return the moment-based estimates. + if support_width <= 0: + return loc_hat, scale_hat + + # Compute the proposed support according to the loc and scale + # estimates. + a_hat = loc_hat + a * scale_hat + b_hat = loc_hat + b * scale_hat + + # Use the moment-based estimates if they are compatible with the data. + data_a = np.min(data) + data_b = np.max(data) + if a_hat < data_a and data_b < b_hat: + return loc_hat, scale_hat + + # Otherwise find other estimates that are compatible with the data. + data_width = data_b - data_a + rel_margin = 0.1 + margin = data_width * rel_margin + + # For a finite interval, both the location and scale + # should have interesting values. + if support_width < np.inf: + loc_hat = (data_a - a) - margin + scale_hat = (data_width + 2 * margin) / support_width + return loc_hat, scale_hat + + # For a one-sided interval, use only an interesting location parameter. + if a > -np.inf: + return (data_a - a) - margin, 1 + elif b < np.inf: + return (data_b - b) + margin, 1 + else: + raise RuntimeError + + def fit_loc_scale(self, data, *args): + """ + Estimate loc and scale parameters from data using 1st and 2nd moments. + + Parameters + ---------- + data : array_like + Data to fit. + arg1, arg2, arg3,... : array_like + The shape parameter(s) for the distribution (see docstring of the + instance object for more information). + + Returns + ------- + Lhat : float + Estimated location parameter for the data. + Shat : float + Estimated scale parameter for the data. + + """ + mu, mu2 = self.stats(*args, **{'moments': 'mv'}) + tmp = asarray(data) + muhat = tmp.mean() + mu2hat = tmp.var() + Shat = sqrt(mu2hat / mu2) + with np.errstate(invalid='ignore'): + Lhat = muhat - Shat*mu + if not np.isfinite(Lhat): + Lhat = 0 + if not (np.isfinite(Shat) and (0 < Shat)): + Shat = 1 + return Lhat, Shat + + def _entropy(self, *args): + def integ(x): + val = self._pdf(x, *args) + return entr(val) + + # upper limit is often inf, so suppress warnings when integrating + _a, _b = self._get_support(*args) + with np.errstate(over='ignore'): + h = integrate.quad(integ, _a, _b)[0] + + if not np.isnan(h): + return h + else: + # try with different limits if integration problems + low, upp = self.ppf([1e-10, 1. - 1e-10], *args) + if np.isinf(_b): + upper = upp + else: + upper = _b + if np.isinf(_a): + lower = low + else: + lower = _a + return integrate.quad(integ, lower, upper)[0] + + def expect(self, func=None, args=(), loc=0, scale=1, lb=None, ub=None, + conditional=False, **kwds): + """Calculate expected value of a function with respect to the + distribution by numerical integration. + + The expected value of a function ``f(x)`` with respect to a + distribution ``dist`` is defined as:: + + ub + E[f(x)] = Integral(f(x) * dist.pdf(x)), + lb + + where ``ub`` and ``lb`` are arguments and ``x`` has the ``dist.pdf(x)`` + distribution. If the bounds ``lb`` and ``ub`` correspond to the + support of the distribution, e.g. ``[-inf, inf]`` in the default + case, then the integral is the unrestricted expectation of ``f(x)``. + Also, the function ``f(x)`` may be defined such that ``f(x)`` is ``0`` + outside a finite interval in which case the expectation is + calculated within the finite range ``[lb, ub]``. + + Parameters + ---------- + func : callable, optional + Function for which integral is calculated. Takes only one argument. + The default is the identity mapping f(x) = x. + args : tuple, optional + Shape parameters of the distribution. + loc : float, optional + Location parameter (default=0). + scale : float, optional + Scale parameter (default=1). + lb, ub : scalar, optional + Lower and upper bound for integration. Default is set to the + support of the distribution. + conditional : bool, optional + If True, the integral is corrected by the conditional probability + of the integration interval. The return value is the expectation + of the function, conditional on being in the given interval. + Default is False. + + Additional keyword arguments are passed to the integration routine. + + Returns + ------- + expect : float + The calculated expected value. + + Notes + ----- + The integration behavior of this function is inherited from + `scipy.integrate.quad`. Neither this function nor + `scipy.integrate.quad` can verify whether the integral exists or is + finite. For example ``cauchy(0).mean()`` returns ``np.nan`` and + ``cauchy(0).expect()`` returns ``0.0``. + + Likewise, the accuracy of results is not verified by the function. + `scipy.integrate.quad` is typically reliable for integrals that are + numerically favorable, but it is not guaranteed to converge + to a correct value for all possible intervals and integrands. This + function is provided for convenience; for critical applications, + check results against other integration methods. + + The function is not vectorized. + + Examples + -------- + + To understand the effect of the bounds of integration consider + + >>> from scipy.stats import expon + >>> expon(1).expect(lambda x: 1, lb=0.0, ub=2.0) + 0.6321205588285578 + + This is close to + + >>> expon(1).cdf(2.0) - expon(1).cdf(0.0) + 0.6321205588285577 + + If ``conditional=True`` + + >>> expon(1).expect(lambda x: 1, lb=0.0, ub=2.0, conditional=True) + 1.0000000000000002 + + The slight deviation from 1 is due to numerical integration. + + The integrand can be treated as a complex-valued function + by passing ``complex_func=True`` to `scipy.integrate.quad` . + + >>> import numpy as np + >>> from scipy.stats import vonmises + >>> res = vonmises(loc=2, kappa=1).expect(lambda x: np.exp(1j*x), + ... complex_func=True) + >>> res + (-0.18576377217422957+0.40590124735052263j) + + >>> np.angle(res) # location of the (circular) distribution + 2.0 + + """ + lockwds = {'loc': loc, + 'scale': scale} + self._argcheck(*args) + _a, _b = self._get_support(*args) + if func is None: + def fun(x, *args): + return x * self.pdf(x, *args, **lockwds) + else: + def fun(x, *args): + return func(x) * self.pdf(x, *args, **lockwds) + if lb is None: + lb = loc + _a * scale + if ub is None: + ub = loc + _b * scale + + cdf_bounds = self.cdf([lb, ub], *args, **lockwds) + invfac = cdf_bounds[1] - cdf_bounds[0] + + kwds['args'] = args + + # split interval to help integrator w/ infinite support; see gh-8928 + alpha = 0.05 # split body from tails at probability mass `alpha` + inner_bounds = np.array([alpha, 1-alpha]) + cdf_inner_bounds = cdf_bounds[0] + invfac * inner_bounds + c, d = loc + self._ppf(cdf_inner_bounds, *args) * scale + + # Do not silence warnings from integration. + lbc = integrate.quad(fun, lb, c, **kwds)[0] + cd = integrate.quad(fun, c, d, **kwds)[0] + dub = integrate.quad(fun, d, ub, **kwds)[0] + vals = (lbc + cd + dub) + + if conditional: + vals /= invfac + return np.array(vals)[()] # make it a numpy scalar like other methods + + def _param_info(self): + shape_info = self._shape_info() + loc_info = _ShapeInfo("loc", False, (-np.inf, np.inf), (False, False)) + scale_info = _ShapeInfo("scale", False, (0, np.inf), (False, False)) + param_info = shape_info + [loc_info, scale_info] + return param_info + + # For now, _delta_cdf is a private method. + def _delta_cdf(self, x1, x2, *args, loc=0, scale=1): + """ + Compute CDF(x2) - CDF(x1). + + Where x1 is greater than the median, compute SF(x1) - SF(x2), + otherwise compute CDF(x2) - CDF(x1). + + This function is only useful if `dist.sf(x, ...)` has an implementation + that is numerically more accurate than `1 - dist.cdf(x, ...)`. + """ + cdf1 = self.cdf(x1, *args, loc=loc, scale=scale) + # Possible optimizations (needs investigation-these might not be + # better): + # * Use _lazywhere instead of np.where + # * Instead of cdf1 > 0.5, compare x1 to the median. + result = np.where(cdf1 > 0.5, + (self.sf(x1, *args, loc=loc, scale=scale) + - self.sf(x2, *args, loc=loc, scale=scale)), + self.cdf(x2, *args, loc=loc, scale=scale) - cdf1) + if result.ndim == 0: + result = result[()] + return result + + +# Helpers for the discrete distributions +def _drv2_moment(self, n, *args): + """Non-central moment of discrete distribution.""" + def fun(x): + return np.power(x, n) * self._pmf(x, *args) + + _a, _b = self._get_support(*args) + return _expect(fun, _a, _b, self.ppf(0.5, *args), self.inc) + + +def _drv2_ppfsingle(self, q, *args): # Use basic bisection algorithm + _a, _b = self._get_support(*args) + b = _b + a = _a + if isinf(b): # Be sure ending point is > q + b = int(max(100*q, 10)) + while 1: + if b >= _b: + qb = 1.0 + break + qb = self._cdf(b, *args) + if (qb < q): + b += 10 + else: + break + else: + qb = 1.0 + if isinf(a): # be sure starting point < q + a = int(min(-100*q, -10)) + while 1: + if a <= _a: + qb = 0.0 + break + qa = self._cdf(a, *args) + if (qa > q): + a -= 10 + else: + break + else: + qa = self._cdf(a, *args) + + while 1: + if (qa == q): + return a + if (qb == q): + return b + if b <= a+1: + if qa > q: + return a + else: + return b + c = int((a+b)/2.0) + qc = self._cdf(c, *args) + if (qc < q): + if a != c: + a = c + else: + raise RuntimeError('updating stopped, endless loop') + qa = qc + elif (qc > q): + if b != c: + b = c + else: + raise RuntimeError('updating stopped, endless loop') + qb = qc + else: + return c + + +# Must over-ride one of _pmf or _cdf or pass in +# x_k, p(x_k) lists in initialization + + +class rv_discrete(rv_generic): + """A generic discrete random variable class meant for subclassing. + + `rv_discrete` is a base class to construct specific distribution classes + and instances for discrete random variables. It can also be used + to construct an arbitrary distribution defined by a list of support + points and corresponding probabilities. + + Parameters + ---------- + a : float, optional + Lower bound of the support of the distribution, default: 0 + b : float, optional + Upper bound of the support of the distribution, default: plus infinity + moment_tol : float, optional + The tolerance for the generic calculation of moments. + values : tuple of two array_like, optional + ``(xk, pk)`` where ``xk`` are integers and ``pk`` are the non-zero + probabilities between 0 and 1 with ``sum(pk) = 1``. ``xk`` + and ``pk`` must have the same shape, and ``xk`` must be unique. + inc : integer, optional + Increment for the support of the distribution. + Default is 1. (other values have not been tested) + badvalue : float, optional + The value in a result arrays that indicates a value that for which + some argument restriction is violated, default is np.nan. + name : str, optional + The name of the instance. This string is used to construct the default + example for distributions. + longname : str, optional + This string is used as part of the first line of the docstring returned + when a subclass has no docstring of its own. Note: `longname` exists + for backwards compatibility, do not use for new subclasses. + shapes : str, optional + The shape of the distribution. For example "m, n" for a distribution + that takes two integers as the two shape arguments for all its methods + If not provided, shape parameters will be inferred from + the signatures of the private methods, ``_pmf`` and ``_cdf`` of + the instance. + seed : {None, int, `numpy.random.Generator`, `numpy.random.RandomState`}, optional + If `seed` is None (or `np.random`), the `numpy.random.RandomState` + singleton is used. + If `seed` is an int, a new ``RandomState`` instance is used, + seeded with `seed`. + If `seed` is already a ``Generator`` or ``RandomState`` instance then + that instance is used. + + Methods + ------- + rvs + pmf + logpmf + cdf + logcdf + sf + logsf + ppf + isf + moment + stats + entropy + expect + median + mean + std + var + interval + __call__ + support + + Notes + ----- + This class is similar to `rv_continuous`. Whether a shape parameter is + valid is decided by an ``_argcheck`` method (which defaults to checking + that its arguments are strictly positive.) + The main differences are as follows. + + - The support of the distribution is a set of integers. + - Instead of the probability density function, ``pdf`` (and the + corresponding private ``_pdf``), this class defines the + *probability mass function*, `pmf` (and the corresponding + private ``_pmf``.) + - There is no ``scale`` parameter. + - The default implementations of methods (e.g. ``_cdf``) are not designed + for distributions with support that is unbounded below (i.e. + ``a=-np.inf``), so they must be overridden. + + To create a new discrete distribution, we would do the following: + + >>> from scipy.stats import rv_discrete + >>> class poisson_gen(rv_discrete): + ... "Poisson distribution" + ... def _pmf(self, k, mu): + ... return exp(-mu) * mu**k / factorial(k) + + and create an instance:: + + >>> poisson = poisson_gen(name="poisson") + + Note that above we defined the Poisson distribution in the standard form. + Shifting the distribution can be done by providing the ``loc`` parameter + to the methods of the instance. For example, ``poisson.pmf(x, mu, loc)`` + delegates the work to ``poisson._pmf(x-loc, mu)``. + + **Discrete distributions from a list of probabilities** + + Alternatively, you can construct an arbitrary discrete rv defined + on a finite set of values ``xk`` with ``Prob{X=xk} = pk`` by using the + ``values`` keyword argument to the `rv_discrete` constructor. + + **Deepcopying / Pickling** + + If a distribution or frozen distribution is deepcopied (pickled/unpickled, + etc.), any underlying random number generator is deepcopied with it. An + implication is that if a distribution relies on the singleton RandomState + before copying, it will rely on a copy of that random state after copying, + and ``np.random.seed`` will no longer control the state. + + Examples + -------- + Custom made discrete distribution: + + >>> import numpy as np + >>> from scipy import stats + >>> xk = np.arange(7) + >>> pk = (0.1, 0.2, 0.3, 0.1, 0.1, 0.0, 0.2) + >>> custm = stats.rv_discrete(name='custm', values=(xk, pk)) + >>> + >>> import matplotlib.pyplot as plt + >>> fig, ax = plt.subplots(1, 1) + >>> ax.plot(xk, custm.pmf(xk), 'ro', ms=12, mec='r') + >>> ax.vlines(xk, 0, custm.pmf(xk), colors='r', lw=4) + >>> plt.show() + + Random number generation: + + >>> R = custm.rvs(size=100) + + """ + def __new__(cls, a=0, b=inf, name=None, badvalue=None, + moment_tol=1e-8, values=None, inc=1, longname=None, + shapes=None, seed=None): + + if values is not None: + # dispatch to a subclass + return super().__new__(rv_sample) + else: + # business as usual + return super().__new__(cls) + + def __init__(self, a=0, b=inf, name=None, badvalue=None, + moment_tol=1e-8, values=None, inc=1, longname=None, + shapes=None, seed=None): + + super().__init__(seed) + + # cf generic freeze + self._ctor_param = dict( + a=a, b=b, name=name, badvalue=badvalue, + moment_tol=moment_tol, values=values, inc=inc, + longname=longname, shapes=shapes, seed=seed) + + if badvalue is None: + badvalue = nan + self.badvalue = badvalue + self.a = a + self.b = b + self.moment_tol = moment_tol + self.inc = inc + self.shapes = shapes + + if values is not None: + raise ValueError("rv_discrete.__init__(..., values != None, ...)") + + self._construct_argparser(meths_to_inspect=[self._pmf, self._cdf], + locscale_in='loc=0', + # scale=1 for discrete RVs + locscale_out='loc, 1') + self._attach_methods() + self._construct_docstrings(name, longname) + + def __getstate__(self): + dct = self.__dict__.copy() + # these methods will be remade in __setstate__ + attrs = ["_parse_args", "_parse_args_stats", "_parse_args_rvs", + "_cdfvec", "_ppfvec", "generic_moment"] + [dct.pop(attr, None) for attr in attrs] + return dct + + def _attach_methods(self): + """Attaches dynamically created methods to the rv_discrete instance.""" + self._cdfvec = vectorize(self._cdf_single, otypes='d') + self.vecentropy = vectorize(self._entropy) + + # _attach_methods is responsible for calling _attach_argparser_methods + self._attach_argparser_methods() + + # nin correction needs to be after we know numargs + # correct nin for generic moment vectorization + _vec_generic_moment = vectorize(_drv2_moment, otypes='d') + _vec_generic_moment.nin = self.numargs + 2 + self.generic_moment = types.MethodType(_vec_generic_moment, self) + + # correct nin for ppf vectorization + _vppf = vectorize(_drv2_ppfsingle, otypes='d') + _vppf.nin = self.numargs + 2 + self._ppfvec = types.MethodType(_vppf, self) + + # now that self.numargs is defined, we can adjust nin + self._cdfvec.nin = self.numargs + 1 + + def _construct_docstrings(self, name, longname): + if name is None: + name = 'Distribution' + self.name = name + + # generate docstring for subclass instances + if longname is None: + if name[0] in ['aeiouAEIOU']: + hstr = "An " + else: + hstr = "A " + longname = hstr + name + + if sys.flags.optimize < 2: + # Skip adding docstrings if interpreter is run with -OO + if self.__doc__ is None: + self._construct_default_doc(longname=longname, + docdict=docdict_discrete, + discrete='discrete') + else: + dct = dict(distdiscrete) + self._construct_doc(docdict_discrete, dct.get(self.name)) + + # discrete RV do not have the scale parameter, remove it + self.__doc__ = self.__doc__.replace( + '\n scale : array_like, ' + 'optional\n scale parameter (default=1)', '') + + def _updated_ctor_param(self): + """Return the current version of _ctor_param, possibly updated by user. + + Used by freezing. + Keep this in sync with the signature of __init__. + """ + dct = self._ctor_param.copy() + dct['a'] = self.a + dct['b'] = self.b + dct['badvalue'] = self.badvalue + dct['moment_tol'] = self.moment_tol + dct['inc'] = self.inc + dct['name'] = self.name + dct['shapes'] = self.shapes + return dct + + def _nonzero(self, k, *args): + return floor(k) == k + + def _pmf(self, k, *args): + return self._cdf(k, *args) - self._cdf(k-1, *args) + + def _logpmf(self, k, *args): + return log(self._pmf(k, *args)) + + def _logpxf(self, k, *args): + # continuous distributions have PDF, discrete have PMF, but sometimes + # the distinction doesn't matter. This lets us use `_logpxf` for both + # discrete and continuous distributions. + return self._logpmf(k, *args) + + def _unpack_loc_scale(self, theta): + try: + loc = theta[-1] + scale = 1 + args = tuple(theta[:-1]) + except IndexError as e: + raise ValueError("Not enough input arguments.") from e + return loc, scale, args + + def _cdf_single(self, k, *args): + _a, _b = self._get_support(*args) + m = arange(int(_a), k+1) + return np.sum(self._pmf(m, *args), axis=0) + + def _cdf(self, x, *args): + k = floor(x) + return self._cdfvec(k, *args) + + # generic _logcdf, _sf, _logsf, _ppf, _isf, _rvs defined in rv_generic + + def rvs(self, *args, **kwargs): + """Random variates of given type. + + Parameters + ---------- + arg1, arg2, arg3,... : array_like + The shape parameter(s) for the distribution (see docstring of the + instance object for more information). + loc : array_like, optional + Location parameter (default=0). + size : int or tuple of ints, optional + Defining number of random variates (Default is 1). Note that `size` + has to be given as keyword, not as positional argument. + random_state : {None, int, `numpy.random.Generator`, + `numpy.random.RandomState`}, optional + + If `random_state` is None (or `np.random`), the + `numpy.random.RandomState` singleton is used. + If `random_state` is an int, a new ``RandomState`` instance is + used, seeded with `random_state`. + If `random_state` is already a ``Generator`` or ``RandomState`` + instance, that instance is used. + + Returns + ------- + rvs : ndarray or scalar + Random variates of given `size`. + + """ + kwargs['discrete'] = True + return super().rvs(*args, **kwargs) + + def pmf(self, k, *args, **kwds): + """Probability mass function at k of the given RV. + + Parameters + ---------- + k : array_like + Quantiles. + arg1, arg2, arg3,... : array_like + The shape parameter(s) for the distribution (see docstring of the + instance object for more information) + loc : array_like, optional + Location parameter (default=0). + + Returns + ------- + pmf : array_like + Probability mass function evaluated at k + + """ + args, loc, _ = self._parse_args(*args, **kwds) + k, loc = map(asarray, (k, loc)) + args = tuple(map(asarray, args)) + _a, _b = self._get_support(*args) + k = asarray(k-loc) + cond0 = self._argcheck(*args) + cond1 = (k >= _a) & (k <= _b) + if not isinstance(self, rv_sample): + cond1 = cond1 & self._nonzero(k, *args) + cond = cond0 & cond1 + output = zeros(shape(cond), 'd') + place(output, (1-cond0) + np.isnan(k), self.badvalue) + if np.any(cond): + goodargs = argsreduce(cond, *((k,)+args)) + place(output, cond, np.clip(self._pmf(*goodargs), 0, 1)) + if output.ndim == 0: + return output[()] + return output + + def logpmf(self, k, *args, **kwds): + """Log of the probability mass function at k of the given RV. + + Parameters + ---------- + k : array_like + Quantiles. + arg1, arg2, arg3,... : array_like + The shape parameter(s) for the distribution (see docstring of the + instance object for more information). + loc : array_like, optional + Location parameter. Default is 0. + + Returns + ------- + logpmf : array_like + Log of the probability mass function evaluated at k. + + """ + args, loc, _ = self._parse_args(*args, **kwds) + k, loc = map(asarray, (k, loc)) + args = tuple(map(asarray, args)) + _a, _b = self._get_support(*args) + k = asarray(k-loc) + cond0 = self._argcheck(*args) + cond1 = (k >= _a) & (k <= _b) + if not isinstance(self, rv_sample): + cond1 = cond1 & self._nonzero(k, *args) + cond = cond0 & cond1 + output = empty(shape(cond), 'd') + output.fill(-inf) + place(output, (1-cond0) + np.isnan(k), self.badvalue) + if np.any(cond): + goodargs = argsreduce(cond, *((k,)+args)) + place(output, cond, self._logpmf(*goodargs)) + if output.ndim == 0: + return output[()] + return output + + def cdf(self, k, *args, **kwds): + """Cumulative distribution function of the given RV. + + Parameters + ---------- + k : array_like, int + Quantiles. + arg1, arg2, arg3,... : array_like + The shape parameter(s) for the distribution (see docstring of the + instance object for more information). + loc : array_like, optional + Location parameter (default=0). + + Returns + ------- + cdf : ndarray + Cumulative distribution function evaluated at `k`. + + """ + args, loc, _ = self._parse_args(*args, **kwds) + k, loc = map(asarray, (k, loc)) + args = tuple(map(asarray, args)) + _a, _b = self._get_support(*args) + k = asarray(k-loc) + cond0 = self._argcheck(*args) + cond1 = (k >= _a) & (k < _b) + cond2 = (k >= _b) + cond3 = np.isneginf(k) + cond = cond0 & cond1 & np.isfinite(k) + + output = zeros(shape(cond), 'd') + place(output, cond2*(cond0 == cond0), 1.0) + place(output, cond3*(cond0 == cond0), 0.0) + place(output, (1-cond0) + np.isnan(k), self.badvalue) + + if np.any(cond): + goodargs = argsreduce(cond, *((k,)+args)) + place(output, cond, np.clip(self._cdf(*goodargs), 0, 1)) + if output.ndim == 0: + return output[()] + return output + + def logcdf(self, k, *args, **kwds): + """Log of the cumulative distribution function at k of the given RV. + + Parameters + ---------- + k : array_like, int + Quantiles. + arg1, arg2, arg3,... : array_like + The shape parameter(s) for the distribution (see docstring of the + instance object for more information). + loc : array_like, optional + Location parameter (default=0). + + Returns + ------- + logcdf : array_like + Log of the cumulative distribution function evaluated at k. + + """ + args, loc, _ = self._parse_args(*args, **kwds) + k, loc = map(asarray, (k, loc)) + args = tuple(map(asarray, args)) + _a, _b = self._get_support(*args) + k = asarray(k-loc) + cond0 = self._argcheck(*args) + cond1 = (k >= _a) & (k < _b) + cond2 = (k >= _b) + cond = cond0 & cond1 + output = empty(shape(cond), 'd') + output.fill(-inf) + place(output, (1-cond0) + np.isnan(k), self.badvalue) + place(output, cond2*(cond0 == cond0), 0.0) + + if np.any(cond): + goodargs = argsreduce(cond, *((k,)+args)) + place(output, cond, self._logcdf(*goodargs)) + if output.ndim == 0: + return output[()] + return output + + def sf(self, k, *args, **kwds): + """Survival function (1 - `cdf`) at k of the given RV. + + Parameters + ---------- + k : array_like + Quantiles. + arg1, arg2, arg3,... : array_like + The shape parameter(s) for the distribution (see docstring of the + instance object for more information). + loc : array_like, optional + Location parameter (default=0). + + Returns + ------- + sf : array_like + Survival function evaluated at k. + + """ + args, loc, _ = self._parse_args(*args, **kwds) + k, loc = map(asarray, (k, loc)) + args = tuple(map(asarray, args)) + _a, _b = self._get_support(*args) + k = asarray(k-loc) + cond0 = self._argcheck(*args) + cond1 = (k >= _a) & (k < _b) + cond2 = ((k < _a) | np.isneginf(k)) & cond0 + cond = cond0 & cond1 & np.isfinite(k) + output = zeros(shape(cond), 'd') + place(output, (1-cond0) + np.isnan(k), self.badvalue) + place(output, cond2, 1.0) + if np.any(cond): + goodargs = argsreduce(cond, *((k,)+args)) + place(output, cond, np.clip(self._sf(*goodargs), 0, 1)) + if output.ndim == 0: + return output[()] + return output + + def logsf(self, k, *args, **kwds): + """Log of the survival function of the given RV. + + Returns the log of the "survival function," defined as 1 - `cdf`, + evaluated at `k`. + + Parameters + ---------- + k : array_like + Quantiles. + arg1, arg2, arg3,... : array_like + The shape parameter(s) for the distribution (see docstring of the + instance object for more information). + loc : array_like, optional + Location parameter (default=0). + + Returns + ------- + logsf : ndarray + Log of the survival function evaluated at `k`. + + """ + args, loc, _ = self._parse_args(*args, **kwds) + k, loc = map(asarray, (k, loc)) + args = tuple(map(asarray, args)) + _a, _b = self._get_support(*args) + k = asarray(k-loc) + cond0 = self._argcheck(*args) + cond1 = (k >= _a) & (k < _b) + cond2 = (k < _a) & cond0 + cond = cond0 & cond1 + output = empty(shape(cond), 'd') + output.fill(-inf) + place(output, (1-cond0) + np.isnan(k), self.badvalue) + place(output, cond2, 0.0) + if np.any(cond): + goodargs = argsreduce(cond, *((k,)+args)) + place(output, cond, self._logsf(*goodargs)) + if output.ndim == 0: + return output[()] + return output + + def ppf(self, q, *args, **kwds): + """Percent point function (inverse of `cdf`) at q of the given RV. + + Parameters + ---------- + q : array_like + Lower tail probability. + arg1, arg2, arg3,... : array_like + The shape parameter(s) for the distribution (see docstring of the + instance object for more information). + loc : array_like, optional + Location parameter (default=0). + + Returns + ------- + k : array_like + Quantile corresponding to the lower tail probability, q. + + """ + args, loc, _ = self._parse_args(*args, **kwds) + q, loc = map(asarray, (q, loc)) + args = tuple(map(asarray, args)) + _a, _b = self._get_support(*args) + cond0 = self._argcheck(*args) & (loc == loc) + cond1 = (q > 0) & (q < 1) + cond2 = (q == 1) & cond0 + cond = cond0 & cond1 + output = np.full(shape(cond), fill_value=self.badvalue, dtype='d') + # output type 'd' to handle nin and inf + place(output, (q == 0)*(cond == cond), _a-1 + loc) + place(output, cond2, _b + loc) + if np.any(cond): + goodargs = argsreduce(cond, *((q,)+args+(loc,))) + loc, goodargs = goodargs[-1], goodargs[:-1] + place(output, cond, self._ppf(*goodargs) + loc) + + if output.ndim == 0: + return output[()] + return output + + def isf(self, q, *args, **kwds): + """Inverse survival function (inverse of `sf`) at q of the given RV. + + Parameters + ---------- + q : array_like + Upper tail probability. + arg1, arg2, arg3,... : array_like + The shape parameter(s) for the distribution (see docstring of the + instance object for more information). + loc : array_like, optional + Location parameter (default=0). + + Returns + ------- + k : ndarray or scalar + Quantile corresponding to the upper tail probability, q. + + """ + args, loc, _ = self._parse_args(*args, **kwds) + q, loc = map(asarray, (q, loc)) + args = tuple(map(asarray, args)) + _a, _b = self._get_support(*args) + cond0 = self._argcheck(*args) & (loc == loc) + cond1 = (q > 0) & (q < 1) + cond2 = (q == 1) & cond0 + cond3 = (q == 0) & cond0 + cond = cond0 & cond1 + + # same problem as with ppf; copied from ppf and changed + output = np.full(shape(cond), fill_value=self.badvalue, dtype='d') + # output type 'd' to handle nin and inf + lower_bound = _a - 1 + loc + upper_bound = _b + loc + place(output, cond2*(cond == cond), lower_bound) + place(output, cond3*(cond == cond), upper_bound) + + # call place only if at least 1 valid argument + if np.any(cond): + goodargs = argsreduce(cond, *((q,)+args+(loc,))) + loc, goodargs = goodargs[-1], goodargs[:-1] + # PB same as ticket 766 + place(output, cond, self._isf(*goodargs) + loc) + + if output.ndim == 0: + return output[()] + return output + + def _entropy(self, *args): + if hasattr(self, 'pk'): + return stats.entropy(self.pk) + else: + _a, _b = self._get_support(*args) + return _expect(lambda x: entr(self.pmf(x, *args)), + _a, _b, self.ppf(0.5, *args), self.inc) + + def expect(self, func=None, args=(), loc=0, lb=None, ub=None, + conditional=False, maxcount=1000, tolerance=1e-10, chunksize=32): + """ + Calculate expected value of a function with respect to the distribution + for discrete distribution by numerical summation. + + Parameters + ---------- + func : callable, optional + Function for which the expectation value is calculated. + Takes only one argument. + The default is the identity mapping f(k) = k. + args : tuple, optional + Shape parameters of the distribution. + loc : float, optional + Location parameter. + Default is 0. + lb, ub : int, optional + Lower and upper bound for the summation, default is set to the + support of the distribution, inclusive (``lb <= k <= ub``). + conditional : bool, optional + If true then the expectation is corrected by the conditional + probability of the summation interval. The return value is the + expectation of the function, `func`, conditional on being in + the given interval (k such that ``lb <= k <= ub``). + Default is False. + maxcount : int, optional + Maximal number of terms to evaluate (to avoid an endless loop for + an infinite sum). Default is 1000. + tolerance : float, optional + Absolute tolerance for the summation. Default is 1e-10. + chunksize : int, optional + Iterate over the support of a distributions in chunks of this size. + Default is 32. + + Returns + ------- + expect : float + Expected value. + + Notes + ----- + For heavy-tailed distributions, the expected value may or + may not exist, + depending on the function, `func`. If it does exist, but the + sum converges + slowly, the accuracy of the result may be rather low. For instance, for + ``zipf(4)``, accuracy for mean, variance in example is only 1e-5. + increasing `maxcount` and/or `chunksize` may improve the result, + but may also make zipf very slow. + + The function is not vectorized. + + """ + if func is None: + def fun(x): + # loc and args from outer scope + return (x+loc)*self._pmf(x, *args) + else: + def fun(x): + # loc and args from outer scope + return func(x+loc)*self._pmf(x, *args) + # used pmf because _pmf does not check support in randint and there + # might be problems(?) with correct self.a, self.b at this stage maybe + # not anymore, seems to work now with _pmf + + _a, _b = self._get_support(*args) + if lb is None: + lb = _a + else: + lb = lb - loc # convert bound for standardized distribution + if ub is None: + ub = _b + else: + ub = ub - loc # convert bound for standardized distribution + if conditional: + invfac = self.sf(lb-1, *args) - self.sf(ub, *args) + else: + invfac = 1.0 + + if isinstance(self, rv_sample): + res = self._expect(fun, lb, ub) + return res / invfac + + # iterate over the support, starting from the median + x0 = self.ppf(0.5, *args) + res = _expect(fun, lb, ub, x0, self.inc, maxcount, tolerance, chunksize) + return res / invfac + + def _param_info(self): + shape_info = self._shape_info() + loc_info = _ShapeInfo("loc", True, (-np.inf, np.inf), (False, False)) + param_info = shape_info + [loc_info] + return param_info + + +def _expect(fun, lb, ub, x0, inc, maxcount=1000, tolerance=1e-10, + chunksize=32): + """Helper for computing the expectation value of `fun`.""" + # short-circuit if the support size is small enough + if (ub - lb) <= chunksize: + supp = np.arange(lb, ub+1, inc) + vals = fun(supp) + return np.sum(vals) + + # otherwise, iterate starting from x0 + if x0 < lb: + x0 = lb + if x0 > ub: + x0 = ub + + count, tot = 0, 0. + # iterate over [x0, ub] inclusive + for x in _iter_chunked(x0, ub+1, chunksize=chunksize, inc=inc): + count += x.size + delta = np.sum(fun(x)) + tot += delta + if abs(delta) < tolerance * x.size: + break + if count > maxcount: + warnings.warn('expect(): sum did not converge', + RuntimeWarning, stacklevel=3) + return tot + + # iterate over [lb, x0) + for x in _iter_chunked(x0-1, lb-1, chunksize=chunksize, inc=-inc): + count += x.size + delta = np.sum(fun(x)) + tot += delta + if abs(delta) < tolerance * x.size: + break + if count > maxcount: + warnings.warn('expect(): sum did not converge', + RuntimeWarning, stacklevel=3) + break + + return tot + + +def _iter_chunked(x0, x1, chunksize=4, inc=1): + """Iterate from x0 to x1 in chunks of chunksize and steps inc. + + x0 must be finite, x1 need not be. In the latter case, the iterator is + infinite. + Handles both x0 < x1 and x0 > x1. In the latter case, iterates downwards + (make sure to set inc < 0.) + + >>> from scipy.stats._distn_infrastructure import _iter_chunked + >>> [x for x in _iter_chunked(2, 5, inc=2)] + [array([2, 4])] + >>> [x for x in _iter_chunked(2, 11, inc=2)] + [array([2, 4, 6, 8]), array([10])] + >>> [x for x in _iter_chunked(2, -5, inc=-2)] + [array([ 2, 0, -2, -4])] + >>> [x for x in _iter_chunked(2, -9, inc=-2)] + [array([ 2, 0, -2, -4]), array([-6, -8])] + + """ + if inc == 0: + raise ValueError('Cannot increment by zero.') + if chunksize <= 0: + raise ValueError('Chunk size must be positive; got %s.' % chunksize) + + s = 1 if inc > 0 else -1 + stepsize = abs(chunksize * inc) + + x = x0 + while (x - x1) * inc < 0: + delta = min(stepsize, abs(x - x1)) + step = delta * s + supp = np.arange(x, x + step, inc) + x += step + yield supp + + +class rv_sample(rv_discrete): + """A 'sample' discrete distribution defined by the support and values. + + The ctor ignores most of the arguments, only needs the `values` argument. + """ + + def __init__(self, a=0, b=inf, name=None, badvalue=None, + moment_tol=1e-8, values=None, inc=1, longname=None, + shapes=None, seed=None): + + super(rv_discrete, self).__init__(seed) + + if values is None: + raise ValueError("rv_sample.__init__(..., values=None,...)") + + # cf generic freeze + self._ctor_param = dict( + a=a, b=b, name=name, badvalue=badvalue, + moment_tol=moment_tol, values=values, inc=inc, + longname=longname, shapes=shapes, seed=seed) + + if badvalue is None: + badvalue = nan + self.badvalue = badvalue + self.moment_tol = moment_tol + self.inc = inc + self.shapes = shapes + self.vecentropy = self._entropy + + xk, pk = values + + if np.shape(xk) != np.shape(pk): + raise ValueError("xk and pk must have the same shape.") + if np.less(pk, 0.0).any(): + raise ValueError("All elements of pk must be non-negative.") + if not np.allclose(np.sum(pk), 1): + raise ValueError("The sum of provided pk is not 1.") + if not len(set(np.ravel(xk))) == np.size(xk): + raise ValueError("xk may not contain duplicate values.") + + indx = np.argsort(np.ravel(xk)) + self.xk = np.take(np.ravel(xk), indx, 0) + self.pk = np.take(np.ravel(pk), indx, 0) + self.a = self.xk[0] + self.b = self.xk[-1] + + self.qvals = np.cumsum(self.pk, axis=0) + + self.shapes = ' ' # bypass inspection + + self._construct_argparser(meths_to_inspect=[self._pmf], + locscale_in='loc=0', + # scale=1 for discrete RVs + locscale_out='loc, 1') + + self._attach_methods() + + self._construct_docstrings(name, longname) + + def __getstate__(self): + dct = self.__dict__.copy() + + # these methods will be remade in rv_generic.__setstate__, + # which calls rv_generic._attach_methods + attrs = ["_parse_args", "_parse_args_stats", "_parse_args_rvs"] + [dct.pop(attr, None) for attr in attrs] + + return dct + + def _attach_methods(self): + """Attaches dynamically created argparser methods.""" + self._attach_argparser_methods() + + def _get_support(self, *args): + """Return the support of the (unscaled, unshifted) distribution. + + Parameters + ---------- + arg1, arg2, ... : array_like + The shape parameter(s) for the distribution (see docstring of the + instance object for more information). + + Returns + ------- + a, b : numeric (float, or int or +/-np.inf) + end-points of the distribution's support. + """ + return self.a, self.b + + def _pmf(self, x): + return np.select([x == k for k in self.xk], + [np.broadcast_arrays(p, x)[0] for p in self.pk], 0) + + def _cdf(self, x): + xx, xxk = np.broadcast_arrays(x[:, None], self.xk) + indx = np.argmax(xxk > xx, axis=-1) - 1 + return self.qvals[indx] + + def _ppf(self, q): + qq, sqq = np.broadcast_arrays(q[..., None], self.qvals) + indx = argmax(sqq >= qq, axis=-1) + return self.xk[indx] + + def _rvs(self, size=None, random_state=None): + # Need to define it explicitly, otherwise .rvs() with size=None + # fails due to explicit broadcasting in _ppf + U = random_state.uniform(size=size) + if size is None: + U = np.array(U, ndmin=1) + Y = self._ppf(U)[0] + else: + Y = self._ppf(U) + return Y + + def _entropy(self): + return stats.entropy(self.pk) + + def generic_moment(self, n): + n = asarray(n) + return np.sum(self.xk**n[np.newaxis, ...] * self.pk, axis=0) + + def _expect(self, fun, lb, ub, *args, **kwds): + # ignore all args, just do a brute force summation + supp = self.xk[(lb <= self.xk) & (self.xk <= ub)] + vals = fun(supp) + return np.sum(vals) + + +def _check_shape(argshape, size): + """ + This is a utility function used by `_rvs()` in the class geninvgauss_gen. + It compares the tuple argshape to the tuple size. + + Parameters + ---------- + argshape : tuple of integers + Shape of the arguments. + size : tuple of integers or integer + Size argument of rvs(). + + Returns + ------- + The function returns two tuples, scalar_shape and bc. + + scalar_shape : tuple + Shape to which the 1-d array of random variates returned by + _rvs_scalar() is converted when it is copied into the + output array of _rvs(). + + bc : tuple of booleans + bc is an tuple the same length as size. bc[j] is True if the data + associated with that index is generated in one call of _rvs_scalar(). + + """ + scalar_shape = [] + bc = [] + for argdim, sizedim in zip_longest(argshape[::-1], size[::-1], + fillvalue=1): + if sizedim > argdim or (argdim == sizedim == 1): + scalar_shape.append(sizedim) + bc.append(True) + else: + bc.append(False) + return tuple(scalar_shape[::-1]), tuple(bc[::-1]) + + +def get_distribution_names(namespace_pairs, rv_base_class): + """Collect names of statistical distributions and their generators. + + Parameters + ---------- + namespace_pairs : sequence + A snapshot of (name, value) pairs in the namespace of a module. + rv_base_class : class + The base class of random variable generator classes in a module. + + Returns + ------- + distn_names : list of strings + Names of the statistical distributions. + distn_gen_names : list of strings + Names of the generators of the statistical distributions. + Note that these are not simply the names of the statistical + distributions, with a _gen suffix added. + + """ + distn_names = [] + distn_gen_names = [] + for name, value in namespace_pairs: + if name.startswith('_'): + continue + if name.endswith('_gen') and issubclass(value, rv_base_class): + distn_gen_names.append(name) + if isinstance(value, rv_base_class): + distn_names.append(name) + return distn_names, distn_gen_names