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.
-ml
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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