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Re: st: The VARCLUS in SAS versus STATA Cluster Analysis


From   "Nick Cox" <n.j.cox@durham.ac.uk>
To   <statalist@hsphsun2.harvard.edu>
Subject   Re: st: The VARCLUS in SAS versus STATA Cluster Analysis
Date   Wed, 17 Sep 2003 11:10:55 +0100

Pramod Adhikari

> SAS has a VARCLUS procedure (Variable Cluster Analysis) 'to divide a
set of
> variables into nonoverlapping clusters in such a way that each
cluster can
> be interpreted as essentially unidimensional' (Source: SAS
documentation).
> Is there a similar command in STATA that can perform similar
analysis. With
> the existing clustering methods, I can group the variables (after
> transposing observations into variables) using 'generate' command
but the
> standard output from VARCLUS procedure seems easier to interpret.

I can't comment on SAS's procedure, except that the sentence you quote
is
a very strong claim, promising something that in many datasets may be
impossible.
There is a weasel word, "essentially".

If I had a set of continuous variables, then I would explore such
questions in Stata using -pca-. One crux, however, is judging
closeness of
components to variables, for which the correlations between
components and variables are useful information.

In a posting on 28 August, I showed how to do this more
easily using -makematrix- from SSC.

PCA is less appropriate given categorical variables.

Nick
n.j.cox@durham.ac.uk

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