Classification, clustering, and phylogeny estimation
Thu, 21 Aug 2003 16:59:36 +0200
I´m working with metric multidimensional scaling and
trying to implement the Torgerson algorithm in
SAS/IML. The terms I use are all shown in "Theory and
methods of scaling", Torgerson (1958), p.263-268.
Torgerson´s P-matrices are first transformed into
x-matrices (based on Thurstone´s law of comparative
judgment) which contain both estimated differences
between stimuli and missing values.
Computing the matrix of comparative distances in the
next step I meet a problem:
In the formula to solve for the comparative distances
a few averages summed over different indices are
Maybe the problem sounds trivial, but I don´t know if
the missing values have to be regarded computing the
means, or do I simply have to calculate these averages
neglecting all missing values.
Thanks a lot for your help,
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