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

# Copyright 2023 The JAX Authors.
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# Licensed under the Apache License, Version 2.0 (the "License");
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import scipy.stats as osp_stats

from jax import lax
import jax.numpy as jnp
from jax._src.numpy.util import implements, promote_args_inexact
from jax._src.scipy.special import gammaln, xlogy, xlog1py
from jax._src.typing import Array, ArrayLike


[docs] @implements(osp_stats.nbinom.logpmf, update_doc=False) def logpmf(k: ArrayLike, n: ArrayLike, p: ArrayLike, loc: ArrayLike = 0) -> Array: """JAX implementation of scipy.stats.binom.logpmf.""" k, n, p, loc = promote_args_inexact("binom.logpmf", k, n, p, loc) y = lax.sub(k, loc) comb_term = lax.sub( gammaln(n + 1), lax.add(gammaln(y + 1), gammaln(n - y + 1)) ) log_linear_term = lax.add(xlogy(y, p), xlog1py(lax.sub(n, y), lax.neg(p))) log_probs = lax.add(comb_term, log_linear_term) return jnp.where(lax.ge(k, loc) & lax.lt(k, loc + n + 1), log_probs, -jnp.inf)
[docs] @implements(osp_stats.nbinom.pmf, update_doc=False) def pmf(k: ArrayLike, n: ArrayLike, p: ArrayLike, loc: ArrayLike = 0) -> Array: """JAX implementation of scipy.stats.binom.pmf.""" return lax.exp(logpmf(k, n, p, loc))