Thorsten Schäfer created MATH-1031:
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Summary: 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
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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