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RE: st: RE: Re: Cluster Analysis

From   "Michael I. Lichter" <[email protected]>
To   [email protected]
Subject   RE: st: RE: Re: Cluster Analysis
Date   Mon, 20 Oct 2003 12:03:48 -0400

Could Nick or someone else explain (a) what is meant by "continua," and
(b) how you justify & properly handle categorical/dichotomous variables
in PCA? Thanks.


Quoting Nick Cox <[email protected]>:

> 1. You are interested, naturally enough, in correlations 
> among predictors. Whether observations are clustered 
> together is a different issue. It is easy to think 
> of continua with high correlations, continua with 
> low correlations, cluster structure with high 
> correlations and cluster structure with low 
> correlations. 
> 2. If cluster structure exists, it will be evident 
> in plots of the first few principal components. 
> The fact that some of your variables
> are categorical or binary would complicate a PCA without 
> making it impossible. 
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