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From "Jeff Eastman (JIRA)" <>
Subject [jira] [Updated] (MAHOUT-1045) Cluster evaluators returning bad results
Date Thu, 19 Jul 2012 19:43:38 GMT


Jeff Eastman updated MAHOUT-1045:

    Attachment: MAHOUT-1045.patch

This patch adjusts the average intra-cluster density to ignore NaN values by counting the
good ones for the average. It also has two methods:

  public Map<Integer, Vector> interClusterDistances() {
  public Vector intraClusterDensities() {

that provide Java access to these intermediate values before averages are calculated.
> Cluster evaluators returning bad results
> ----------------------------------------
>                 Key: MAHOUT-1045
>                 URL:
>             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, 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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