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Neil and Dirk,

I have tried a dissimilarity matrix of 500 by 500 in SPSS Proxscal (ordinal)
and it took about 20 seconds on a pentium 4, 1.5 Ghz. Proxscal is the
program I prefer most for doing MDS at this moment.

Patrick Groenen
-------------------------------------------------
Prof. dr. Patrick J.F. Groenen
Econometric Institute
Erasmus University Rotterdam
Room H11.23
P.O. Box 1738, 3000 DR Rotterdam, The Netherlands
tel:    ++ 31 10 408 1281
fax:    ++ 31 10 408 9162
e-mail: [log in to unmask]
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> -----Original Message-----
> From: Classification, clustering, and phylogeny estimation
> [mailto:[log in to unmask]]On Behalf Of [log in to unmask]
> Sent: Thursday 14 November 2002 18:39
> To: [log in to unmask]
> Subject:
>
>
> Dirk:
>
> MDS using SAS or SPSS will most likely be very slow. I have done
> MDS with SPSS and a matrix of your dimensions and 1 hour later it
> was still running.
>
> If performance is an issue, writting code will always run faster
> then the commercial stat packages. I use IMSL which has an MDS
> function and the runtime results were vastly superior. One reason
> is with SPSS, the GUI slows things done, their code does lots of
> memory allocation, slowing things down also.
>
> "Hand-Rolling" your own code with a proven MDS function (which
> are easy to find) will run much fast as you can just cache (store
> your matrix in memory) and let it fly.
>
> The net conclusion, unless it's a small sample size and I want to
> test my own programs... I compare my results with SPSS to affirm
> the results match. Direct programming is always much faster.
>
> Neil Gottlieb
> Profile Depot, Inc.
>
> you wrote:
> Dear Listmembers,
> I would like to do a MDS with a 400X400 square, symetric matrix of
> (dis)similaritys. Most MDS-Software is limited to a much smaller amount
> of variables though. I have been told, that SAS might be able to process
> the analyis I need, but this is quite inconvenient for me in terms of
> access to the software, hardware-requirements etc. Could anybody tell
> me, if there is a stand-alone program that can do MDS (preferably
> nonmetric) with a matrix of that size?
>
> Thanks a lot for your help,
> dirk
>
> P.S: My Matrix is not suitable for factor analysis and clustering does
> not produce the results I need.
>