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https://issues.apache.org/jira/browse/MAHOUT-825?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13122550#comment-13122550
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Ted Dunning commented on MAHOUT-825:
------------------------------------
{quote}
I experimented with the distance calculation, and now, I am using radius
instead of the t1 parameter.
{code}
private boolean shouldCluster(Canopy canopy, Vector point) {
if (clusterStrictly) {
Vector currentCenter = canopy.getCenter();
double distance = measure.distance(currentCenter.getLengthSquared(),
currentCenter, point);
double radius = canopy.getRadius().getLengthSquared();
return distance < radius*3;
}
return true;
}
{code}
The positives and negatives of this approach are :
+ve : Its not dependent on t1. Radius is, I think a better way to calculate
distances from canopies ( acoording to the discussion above ). I experienced,
that the results are also "much better" than using t1. Some meaningful points,
those were missed by using t1, are being clustered using this approach.
-ve : Now, I have no control on the quality of the cluster. The number, 3, is a
constant. With t1, at least I was able to control the quality of the cluster.
{quote}
> Canopies grouping records outside t1
> ------------------------------------
>
> Key: MAHOUT-825
> URL: https://issues.apache.org/jira/browse/MAHOUT-825
> Project: Mahout
> Issue Type: Bug
> Components: Clustering
> Affects Versions: 0.6
> Environment: windows, linux
> Reporter: Paritosh Ranjan
> Labels: features, newbie, patch
> Fix For: 0.6
>
> Attachments: Clustering Remote Points - Two Big, Useless
> Clusters.txt, Not Clustering Remote Points - Two Meaningful Clusters.txt,
> canopy-clusterFilter-t1, canopy-outside-t1-points-patch-1,
> canopy-strict-clustering-flag
>
>
> While finding closest canopy, there is no check to ensure that it returns
> canopies which are within distance t1 from the point. This results in
> incorrect result i.e. Points outside t1 are grouped in canopies.
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