[R] code for metric / nonmetric MDS

[Jan de Leeuw]

This does metric/nonmetric weighted least squares multidimensional  
scaling
using the smacof algorithm (deleeuw, 1977, in barra et al (eds),  
recent developments
in statistics; or deleeuw and heiser, 1980, in krishnaiah (ed),  
multivariate
analysis V). Uses a dist object for both dissimilarities and weights,
which should both be non-negative for convergence. Fits euclidean
distances only.

Monotone regression is done by pool-adjacent-violators, implemented
in pava.R. The pava function can actually do monotone regression
using weighted means, medians, or p-fractiles -- although for mds
only means are used.

Somebody asked for this and it may be useful to others. It is not  
written
for efficiency, but the flexibility of allowing weights can be handy. By
using relaxed smacof updates (see deleeuw and heiser or the book
by borg and groenen) we can make this about twice as fast -- but that
will come later. Feel free to tinker away.

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Jan de Leeuw, 11667 Steinhoff Rd, Frazier Park, CA 93225, 661-245-1725
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                                      Und die Einen sind im Dunkeln
                                      Und die Andern sind im Licht
                                      Und man siehe die im Lichte
                                      Die im Dunklen sieht man nicht
                                                                         
                                  Brecht