Mailing-List: contact issues-help@commons.apache.org; run by ezmlm
Precedence: bulk
Reply-To: issues@commons.apache.org
Message-ID: <10776101.28321287766157261.JavaMail.jira@thor>
Date: Fri, 22 Oct 2010 12:49:17 -0400 (EDT)
From: "Luc Maisonobe (JIRA)" <jira@apache.org>
To: issues@commons.apache.org
Subject: [jira] Commented: (MATH-429) KMeansPlusPlusClusterer breaks by
 division by zero
In-Reply-To: <20268759.23331287734535844.JavaMail.jira@thor>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 7bit


    [ https://issues.apache.org/jira/browse/MATH-429?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12923906#action_12923906 ] 

Luc Maisonobe commented on MATH-429:
------------------------------------

You have encountered one classical proble with k-means: at some stage (here at the first iteration), one of the clusters becomes empty.
This case is currently no handled by commons-math (which is a bug, so we have to fix it).
When a cluster is empty, a new centroid must be defined from the other clusters. There are different strategies:

# take the point farthest from any cluster
# select a random point from the cluster with the largest distance variance
# select a random point from the cluster with the largest number of points

My prefered choice would be 2, what do other people think ?


> KMeansPlusPlusClusterer breaks by division by zero
> --------------------------------------------------
>
>                 Key: MATH-429
>                 URL: https://issues.apache.org/jira/browse/MATH-429
>             Project: Commons Math
>          Issue Type: Bug
>    Affects Versions: 2.1
>         Environment: Java, Windows
>            Reporter: Erik van Ingen
>            Priority: Blocker
>         Attachments: KMeansPlusPlusClustererTest.java
>
>   Original Estimate: 3h
>  Remaining Estimate: 3h
>
> For a certain space, KMeansPlusPlusClusterer  breaks. This is a blocker because this space occurs in our domain. 

-- 
This message is automatically generated by JIRA.
-
You can reply to this email to add a comment to the issue online.