Source code for jax._src.scipy.stats.poisson

# Copyright 2018 Google LLC
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
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#     https://www.apache.org/licenses/LICENSE-2.0
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# Unless required by applicable law or agreed to in writing, software
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import scipy.stats as osp_stats

from jax import lax
from jax._src.numpy.util import _wraps
from jax._src.numpy import lax_numpy as jnp
from jax.scipy.special import xlogy, gammaln, gammaincc


[docs]@_wraps(osp_stats.poisson.logpmf, update_doc=False) def logpmf(k, mu, loc=0): k, mu, loc = jnp._promote_args_inexact("poisson.logpmf", k, mu, loc) zero = jnp._constant_like(k, 0) x = lax.sub(k, loc) log_probs = xlogy(x, mu) - gammaln(x + 1) - mu return jnp.where(lax.lt(x, zero), -jnp.inf, log_probs)
[docs]@_wraps(osp_stats.poisson.pmf, update_doc=False) def pmf(k, mu, loc=0): return jnp.exp(logpmf(k, mu, loc))
@_wraps(osp_stats.poisson.cdf, update_doc=False) def cdf(k, mu, loc=0): k, mu, loc = jnp._promote_args_inexact("poisson.logpmf", k, mu, loc) zero = jnp._constant_like(k, 0) x = lax.sub(k, loc) p = gammaincc(jnp.floor(1 + x), mu) return jnp.where(lax.lt(x, zero), zero, p)