[R] CLARA and determining the right number of clusters

[Christian Hennig]

Hi there,

generally finding the right number of clusters is a difficult problem and 
depends heavily on the cluster concept needed for the particular 
application.
No outcome of any automatic mathod should be taken for granted.

Having said that, I guess that something like the example given in
> ?pam.object
(replacing pam by clara) should work with clara, too.

Regards,
Christian


On Tue, 30 Sep 2008, pacomet wrote:

> Hi everyone
>
> I have a question about clustering. I've managed using CLARA to get a
> clustering analysis of a large data set. But now I want to find which is the
> right number of clusters.
>
> The clara.object gives some information like the ratio between maximal and
> minimal dissimilarity that says (maybe if lower than 1??) if a cluster is
> well-separated from the other. I've also read something about silhouette and
> abut cluster.stats but can't manage to get how to find the right number of
> clusters.
>
> I've tried a suggestion from the mailing list but when using dist
>
> d1<-dist(mydata$sst)
>
> it says that "specified vector size is too big"
>
> Is there any method to find the right number of clusters when using clara?
> Maybe something I've tried but with a small and simple trick I can't find
>
> Thanks in advance
>
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*** --- ***
Christian Hennig
University College London, Department of Statistical Science
Gower St., London WC1E 6BT, phone +44 207 679 1698
chrish at stats.ucl.ac.uk, www.homepages.ucl.ac.uk/~ucakche