MDS normally works with dissimilarities, not similiarities.
This is true of isoMDS (sic) function (sic), as its help page says.
Remember MASS is support software for a book, and you do not appear to
have consulted that reference material.
So you need to convert your input to a dissimilarity matrix.
It's possible that all you need is D = 1 - S.
On Thu, 28 Aug 2003, Bert, Jacobs wrote:
> I've found a good method to convert the cross-elasticity matrix into a
> similaritymatrix and if I use the Isomsd module from the MASS library I
> receive a normal result but not a usable one.
>
> Because I'm working with cross-elasticities, the higher the value, the more
> similar brands should be and the closer they should be on a plot. On my
> plots they are very far away from each other.
>
> How can I make believe the program that higher values result in higher
> similarities and eventually the closer they should be on the map.
--
Brian D. Ripley, ripley@stats.ox.ac.uk
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
University of Oxford, Tel: +44 1865 272861 (self)
1 South Parks Road, +44 1865 272866 (PA)
Oxford OX1 3TG, UK Fax: +44 1865 272595
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