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From Phil Steitz <phil.ste...@gmail.com>
Subject Fwd: [jira] [Deleted] (MATH-1164) Rare case for updateMembershipMatrix() in FuzzyKMeansClusterer
Date Thu, 06 Nov 2014 21:08:41 GMT
Hey Thomas,

Did you actually mean to delete this?

Phil


-------- Forwarded Message --------
Subject: 	[jira] [Deleted] (MATH-1164) Rare case for
updateMembershipMatrix() in FuzzyKMeansClusterer
Date: 	Thu, 6 Nov 2014 20:19:34 +0000 (UTC)
From: 	Thomas Neidhart (JIRA) <jira@apache.org>
Reply-To: 	issues@commons.apache.org
To: 	issues@commons.apache.org



     [ https://issues.apache.org/jira/browse/MATH-1164?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Thomas Neidhart deleted MATH-1164:
----------------------------------


> Rare case for updateMembershipMatrix() in FuzzyKMeansClusterer
> --------------------------------------------------------------
>
>                 Key: MATH-1164
>                 URL: https://issues.apache.org/jira/browse/MATH-1164
>             Project: Commons Math
>          Issue Type: Bug
>            Reporter: Pashutan Modaresi
>            Priority: Minor
>   Original Estimate: 1h
>  Remaining Estimate: 1h
>
> The function updateMembershipMatrix() in FuzzyKMeansClusterer assigns the points to the
cluster with the highest membership. Consider the following case:
> If the distance between a point and the cluster center is zero, then we will have a cluster
membership of one, and all other membership values will be zero.
> So the if condition:
> if (membershipMatrix[i][j] > maxMembership) {
>                     maxMembership = membershipMatrix[i][j];
>                     newCluster = j;
> }
> will never be true during the for loop and newCluster will remain -1. This will throw
an exception because of the line:
> clusters.get(newCluster)
>                     .addPoint(point);
> Adding the following condition can solve the problem:
> double d;
> if (sum == 0)
> d = 1;
> else
> d = 1.0/sum;



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