From 7b28dce43d2bbaf144b33aae41b048f5404e5a2f Mon Sep 17 00:00:00 2001
From: Ryan Curtin <ryan@ratml.org>
Date: Sat, 26 Sep 2015 04:17:01 +0000
Subject: [PATCH] Fix incremental single-point training.

---
 .../methods/naive_bayes/naive_bayes_classifier_impl.hpp   | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/src/mlpack/methods/naive_bayes/naive_bayes_classifier_impl.hpp b/src/mlpack/methods/naive_bayes/naive_bayes_classifier_impl.hpp
index 9dbd7c533c..21829e3938 100644
--- a/src/mlpack/methods/naive_bayes/naive_bayes_classifier_impl.hpp
+++ b/src/mlpack/methods/naive_bayes/naive_bayes_classifier_impl.hpp
@@ -146,9 +146,11 @@ void NaiveBayesClassifier<MatType>::Train(const VecType& point,
 
   arma::vec delta = point - means.col(label);
   means.col(label) += delta / probabilities[label];
-  variances.col(label) *= (probabilities[label] - 1) / probabilities[label];
-  variances.col(label) += (1 / probabilities[label]) *
-      (delta % (point - means.col(label)));
+  if (probabilities[label] > 2)
+    variances.col(label) *= (probabilities[label] - 2);
+  variances.col(label) += (delta % (point - means.col(label)));
+  if (probabilities[label] > 1)
+    variances.col(label) /= probabilities[label] - 1;
 
   trainingPoints++;
   probabilities /= trainingPoints;