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https://issues.apache.org/jira/browse/MATH-1031?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Thomas Neidhart resolved MATH-1031.
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Resolution: Fixed
Fix Version/s: 3.3
Applied changes in r1542545.
It would be good if we add additional cluster evaluation methods, as described
in
http://en.wikipedia.org/wiki/Cluster_analysis#Evaluation_of_clustering_results
> Refactoring: Move variance calculation of a centroid cluster to its class
> -------------------------------------------------------------------------
>
> Key: MATH-1031
> URL: https://issues.apache.org/jira/browse/MATH-1031
> Project: Commons Math
> Issue Type: Improvement
> Affects Versions: 3.2
> Reporter: Thorsten Schäfer
> Priority: Minor
> Fix For: 3.3
>
> Attachments: centroid.patch
>
>
> Users might be interested in assessing the quality of each cluster in the
> calculated clustering. This can be performed by calculating its variance.
> The variance calculation is actually performed in other places (e.g. for the
> MultiKMeans), but not available to end users.
> I'd propose to add the functionality into the CentroidCluster. The one issue
> to consider is that the cluster does not know based on which distance measure
> it was calculated. In the implementation, I chose to parametrize the method
> with a distance measure which enables users to also compare the quality based
> on various distance measures. Alternatively, it would be possible to add the
> distance measure as a field, which is set by the clustering algorithm.
> In the patch I went for the first method and also changed the 2 other places
> where variance calculation is performed to use the new feature.
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