Source code for jax._src.scipy.stats.chi2

# Copyright 2021 Google LLC
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# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
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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.lax_numpy import _promote_args_inexact, _constant_like, where, inf


[docs]@_wraps(osp_stats.chi2.logpdf, update_doc=False) def logpdf(x, df, loc=0, scale=1): x, df, loc, scale = _promote_args_inexact("chi2.logpdf", x, df, loc, scale) one = _constant_like(x, 1) two = _constant_like(x, 2) y = lax.div(lax.sub(x, loc), scale) df_on_two = lax.div(df, two) kernel = lax.sub(lax.mul(lax.sub(df_on_two, one), lax.log(y)), lax.div(y,two)) nrml_cnst = lax.neg(lax.add(lax.lgamma(df_on_two),lax.div(lax.mul(lax.log(two), df),two))) log_probs = lax.add(lax.sub(nrml_cnst, lax.log(scale)), kernel) return where(lax.lt(x, loc), -inf, log_probs)
[docs]@_wraps(osp_stats.chi2.pdf, update_doc=False) def pdf(x, df, loc=0, scale=1): return lax.exp(logpdf(x, df, loc, scale))