[R] isoMDS and 0 distances

[Jari Oksanen]

On Wed, 2006-04-19 at 07:46 +0100, Prof Brian Ripley wrote:
> Short answer: you cannot compare distances including NAs, so there is no 
> way to find a monotone mapping of distances.
> 
The original Kruskal-Young-Shepard-Torgerson programme KYST (version 1
from 1973) could handle missing values. Unfortunately I've lost the
documents, but if I remember correctly, the argument was that you don't
need but a subset (representative for points) of (dis)similarities to
get a monotone regression. KYST -- and computers of that time (I used
Burroughs!) -- had limitations on data size, and removing some of the
dissimilarities was a way of getting more than 64 data points into
analysis. However, better not go into details since:

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cheers, jari oksanen
-- 
Jari Oksanen -- Biologian laitos, Oulun yliopisto, 90014 Oulu
sposti jari.oksanen at oulu.fi, kotisivu http://cc.oulu.fi/~jarioksa/