[mlpack] 18/324: Don't select points from clusters of size 1.

[Barak A. Pearlmutter]

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bap pushed a commit to branch svn-trunk
in repository mlpack.

commit f4ab5bb379af85d99a292013d224e06570d6d7c1
Author: rcurtin <rcurtin at 9d5b8971-822b-0410-80eb-d18c1038ef23>
Date:   Fri May 23 16:03:41 2014 +0000

    Don't select points from clusters of size 1.
    
    
    git-svn-id: http://svn.cc.gatech.edu/fastlab/mlpack/trunk@16545 9d5b8971-822b-0410-80eb-d18c1038ef23
---
 src/mlpack/methods/kmeans/max_variance_new_cluster_impl.hpp | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/src/mlpack/methods/kmeans/max_variance_new_cluster_impl.hpp b/src/mlpack/methods/kmeans/max_variance_new_cluster_impl.hpp
index e8408a4..c97ef71 100644
--- a/src/mlpack/methods/kmeans/max_variance_new_cluster_impl.hpp
+++ b/src/mlpack/methods/kmeans/max_variance_new_cluster_impl.hpp
@@ -37,8 +37,12 @@ size_t MaxVarianceNewCluster::EmptyCluster(const MatType& data,
   }
 
   // Divide by the number of points in the cluster to produce the variance.
+  // Although a -nan will occur here for the empty cluster(s), this doesn't
+  // matter because variances.max() won't pick it up.  If the number of points
+  // in the cluster is 1, we ensure that cluster is not selected by forcing the
+  // variance to 0.
   for (size_t i = 0; i < clusterCounts.n_elem; ++i)
-    variances[i] /= clusterCounts[i];
+    variances[i] /= (clusterCounts[i] == 1) ? DBL_MAX : clusterCounts[i];
 
   // Now find the cluster with maximum variance.
   arma::uword maxVarCluster;

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