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https://issues.apache.org/jira/browse/MATH-1315?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Gilles Sadowski resolved MATH-1315.
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Fix Version/s: (was: 4.0)
Resolution: Cannot Reproduce
Code has changed, rendering the patch unnecessary (hopefully).
> MultiKMeansPlusPlusClusterer buggy for alternative evaluators
> -------------------------------------------------------------
>
> Key: MATH-1315
> URL: https://issues.apache.org/jira/browse/MATH-1315
> Project: Commons Math
> Issue Type: Bug
> Affects Versions: 3.5
> Reporter: Thorsten Schäfer
> Priority: Major
> Attachments: MATH-1315.patch
>
>
> I just looked into the source code for the MultiKMeansPlusPlusClusterer and
> realized that it would return null in case of an alternative evaluator that
> favors bigger values instead of smaller ones:
> The basic idea of the clustering method is that we perform n clusterings and
> choose the best result. The decision what's the best result is performed by
> the evaluator, which by default assumes smaller values are better.
> According to the documentation, we can also provide a different evaluator,
> which for instance would decide that bigger values are better, but given we
> initialize the best value with Double.POSITIVE_INFINITY in method
> MultiKMeansPlusPlusClusterer.cluster(Collection<T>), we would never find a
> "better" result and thus always return null.
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