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https://issues.apache.org/jira/browse/MAHOUT-1045?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13414791#comment-13414791
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Pat Ferrel edited comment on MAHOUT-1045 at 7/16/12 12:02 AM:
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As to the output per cluster, your description sounds ideal.
The reason for intra-cluster density is to help judge which clusters are really
clumps and which are left-overs or non-clusters. If the distribution of points
in a cluster indicates a "fuzzy" collection it might not be a very high quality
cluster.
As to inter-cluster densities as a quality measure I'd probably calculate an
average to judge a cluster's separation from others in general.
was (Author: pferrel):
As to the output per cluster, your description sounds ideal.
The reason for intra-cluster density is to help judge which clusters are really
clumps and which are left-overs or non-clusters. If the distribution of points
in a cluster indicates a "fuzzy" collection it might not be a very high quality
cluster.
As to inter-cluster distances as a quality measure I'd probably calculate an
average to judge a cluster's separation from others in general.
On the other hand I plan to calculate all inter-cluster distances for another
purpose. If you did it here I'd be forever grateful (which along with $5 will
get you a double tall).
> 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, 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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