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results from sammon()

3 messages · Domenico Cozzetto, Jari Oksanen, Brian Ripley

Domenico Cozzetto
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Dear all,
I'm trying to get a two dimensional embedding of some data using different
meythods, among which princomp(), cmds(), sammon() and isoMDS(). I have a
problem with sammon() because the coordinates I get are all equal to NA.
What does it mean? Why the method fails in finding the coordinates? Can I do
anything to get some meaningful results?
Thank you very much
Domenico
Jari Oksanen
#
On Wed, 2005-04-20 at 10:35 +0200, Domenico Cozzetto wrote:
I'm sorry, but I can't reproduce your problem. I have tried hard with
different tricks, but sammon() always gives good numeric results, or
reports on the problems with the input and refuses to continue. For a
starter: which sammon did you use. I think there may be three or four
implementations in R with that name alone (and some variants may be
names differently). I used sammon() in MASS (Venables & Ripley), and
could not get NA. You need to give more details if you want to get help.

cheers, jari oksanen
Brian Ripley
#
On Wed, 20 Apr 2005, Domenico Cozzetto wrote:

            

      
      
      
    

        
What is cmds()?  There is cmdscale(), but if you have the data (needed to 
use PCA) then classical scaling and PCA are the same thing.

            

      
      
      
    

        
We have no idea. Please read the posting guide and supply some useful 
information and preferably a reproducible example.  One issue is which 
package sammon() came from.

One possible hint if this is sammon() from MASS is to use a different 
starting configuration.