From dhitchco@stat.ufl.edu  Mon May 20 19:34:12 2002
From: dhitchco@stat.ufl.edu (dhitchco@stat.ufl.edu)
Date: Mon, 20 May 2002 20:34:12 +0200 (MET DST)
Subject: [Rd] R bug in cluster package (PR#1580)
Message-ID: <200205201834.UAA29307@pubhealth.ku.dk>

I have apparently found an error in the "pam" function of the "cluster"
library package.  Please pardon me if this error has been pointed out or
if this e-mail should be directed to someone else.

The problem only started occurring with R version 1.5.0, which I started
using about a week ago.  The problem occurs when you try to use "pam"
with the input being a dissimilarity matrix instead of a data matrix;
the results when using the dissimilarity matrix are very strange and not
at all like those obtained when using the data matrix.

For example, try this code:

library(cluster)
data(ruspini)
#the clustering using a data matrix as the input:
pam(ruspini,4)
#the clustering using a dissimilarity matrix as input:
pam(daisy(ruspini),4,diss=T)

The clustering results should be the same but are wildly different.
Again, this problem started happening with the upgrade to R 1.5.0.
Thank you for any help you can provide.

David Hitchcock


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[Rd] R bug in cluster package (PR#1580)
dhitchco@stat.ufl.edu