From 65abbb674195d279608346af3e0c2b367f6e4b33 Mon Sep 17 00:00:00 2001
From: Gael Varoquaux <gael.varoquaux@normalesup.org>
Date: Sun, 6 May 2012 23:21:01 +0200
Subject: [PATCH] ENH: avoid an underflow
---
sklearn/naive_bayes.py | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/sklearn/naive_bayes.py b/sklearn/naive_bayes.py
index eb29765efe..4e7345bf0f 100644
--- a/sklearn/naive_bayes.py
+++ b/sklearn/naive_bayes.py
@@ -266,7 +266,9 @@ class BaseDiscreteNB(BaseNB):
elif self.fit_prior:
# empirical prior, with sample_weight taken into account
y_freq = Y.sum(axis=0)
- self.class_log_prior_ = np.log(y_freq) - np.log(y_freq.sum())
+ eps = np.finfo(1.).eps
+ self.class_log_prior_ = (np.log(y_freq + eps)
+ - np.log(y_freq.sum() + eps))
else:
self.class_log_prior_ = np.zeros(n_classes) - np.log(n_classes)
--
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