R help - Jan 2002 - changing the ordering of leaves in a dendrogram

I'd like to change the way plot.hclust displays an hclust object. Here's

a description of how it's done now, from the R documentation of hclust:


     In hierarchical cluster displays, a decision is needed at each merge
     to specify which subtree should go on the left and which on the right.
     Since, for n observations there are n-1 merges, there are 2^{(n-1)}
     possible orderings for the leaves in a cluster tree, or dendrogram.
     The algorithm used in hclust is to order the subtree so that the
     tighter cluster is on the left (the last, i.e. most recent, merge
     of the left subtree is at a lower value than the last merge of the
     right subtree). Single observations are the tightest clusters possible,
     and merges involving two observations place them in order by their
     observation sequence number.

I have a factor vector (if that's the right term) for the observations, and
I'd like to order the display of the leaves so that leaves of the same
level are grouped together as much as possible.  Even something as simple
as putting the higher average code on the left would help.

I've spent some time looking at the code in rpart, but I'm having a hard
time figuring out what I need to modify.  Or maybe someone's already done
something similar?  Any help much appreciated!

   David Marimont
   NXP Data Analysis, Inc.
   http://www.nxpdata.com

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> I'd like to change the way plot.hclust displays an hclust object.
Here's
> a description of how it's done now, from the R documentation of
hclust:
>
>      In hierarchical cluster displays, a decision is needed at each
merge
>      to specify which subtree should go on the left and which on the
right.
>      Since, for n observations there are n-1 merges, there are
2^{(n-1)}
>      possible orderings for the leaves in a cluster tree, or
dendrogram.
>      The algorithm used in hclust is to order the subtree so that the
>      tighter cluster is on the left (the last, i.e. most recent, merge
>      of the left subtree is at a lower value than the last merge of
the
>      right subtree). Single observations are the tightest clusters
possible,
>      and merges involving two observations place them in order by
their
>      observation sequence number.
>
> I have a factor vector (if that's the right term) for the
observations, and
> I'd like to order the display of the leaves so that leaves of the same
> level are grouped together as much as possible.  Even something as
simple
> as putting the higher average code on the left would help.
>
> I've spent some time looking at the code in rpart, but I'm having a
hard
> time figuring out what I need to modify.  Or maybe someone's already
done
> something similar?  Any help much appreciated!
>
>    David Marimont
>    NXP Data Analysis, Inc.
>    http://www.nxpdata.com
You could look at function group.clust in contributed package maptree
for possible ideas.

Denis White
   US EPA, 200 SW 35th St, Corvallis, Oregon, 97333 USA
   voice: 541.754.4476, email: white.denis at epa.gov
   web: www.epa.gov/wed/pages/staff/white/

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(in the "body", not the subject !)  To: r-help-request at
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