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https://issues.apache.org/jira/browse/MAHOUT-1045?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13417663#comment-13417663
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Jeff Eastman commented on MAHOUT-1045:
--------------------------------------

Good points. I will count the number of non-NaN clusters and divide by that. 
Your other point also deserves thought, though adding near-infinite density to 
the running sum will definitely skew the results. 

I'm going to look into CDbw next...
                
> Cluster evaluators returning bad results
> ----------------------------------------
>
>                 Key: MAHOUT-1045
>                 URL: https://issues.apache.org/jira/browse/MAHOUT-1045
>             Project: Mahout
>          Issue Type: Bug
>          Components: Clustering
>    Affects Versions: 0.6, 0.7, 0.8
>         Environment: Several environments and data sets
>            Reporter: Pat Ferrel
>             Fix For: 0.8
>
>         Attachments: MAHOUT-1045.patch, MAHOUT-1045.patch, 
> first-time-density-nan.txt
>
>
> With real world crawl data the Intra-cluster density from ClusterEvaluator is 
> almost always NaN. The CDbw inter-cluster density is almost always 0. I have 
> also seen several cases where CDbw fails to return any results but have not 
> tracked down why yet.
> I have sent a link to an 8G data set that reproduces these errors to Jeff 
> Eastman.

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