On Wed, 8 Sep 2004, Doran, Harold wrote: > 1) Can isoMDS work only with dissimilarities? Or, is there a way > that it can perform the analysis on the similarity matrix as I have > described it?
Yes. The method, as well as the function in package MASS. All other MDS packages are doing a conversion, probably without telling you how. > 2) If I cannot perform the analysis on the similarity matrix, how > can I turn this matrix into a dissimilarity matrix necessary? I am less > familiar with this matrix and how it would be constructed? Normally similarities are in the range [0,1], and people use D = 1 - S or sqrt(1-S). (Which does not matter for isoMDS since it only uses ranks of dissimilarities, apart from finding the starting configuration.) See the references on the help page for isoMDS. -- Brian D. Ripley, [EMAIL PROTECTED] 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 ______________________________________________ [EMAIL PROTECTED] mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
