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st: -factor pcf- vs -pca- (was factor score postestimation)


From   "Garrard, Wendy M." <wendy.garrard@Vanderbilt.Edu>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: -factor pcf- vs -pca- (was factor score postestimation)
Date   Sun, 11 Sep 2005 10:34:42 -0500

Nick,
Thanks very much. The "predict" is just what I needed.  Also, I
appreciate your suggestion about using pca instead of factor since I am
using regression. I had noticed Stata has two commands that do principal
components; pca, and the pcf option within factor. I generally use the
pcf  factor option, since I usually want to reduce several predictor
variables to a single factor for purposes of regression. 
 
I am a bit confused about the difference Stata is making with --pca--
and --factor, pcf--, and should undoubtedly become familiar with this.
Would you mind pointing out the gist, and perhaps a reference for more
detail?
 
Thanks very much,
wg

________________________________

From: owner-statalist@hsphsun2.harvard.edu on behalf of Nick Cox
Sent: Fri 9/9/2005 9:42 AM
To: statalist@hsphsun2.harvard.edu
Subject: st: RE: Factor score, postestimation question

-factor- and -pca- have been revised so that their
behaviour is closer to that of other commands. The main
idea now is to use -predict- instead. 

As you want to proceed to a regression, -pca-
would sound a more obvious choice.

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

Garrard, Wendy M.

> There seems to be a change (in v. 9) in how one gets factor scores.
> Previously (v. 8) I simply used < score factorname > after an analysis
> run, but now that returns an error message that "score is not valid
> after factor.
>
> I have checked the help files, etc. but the terms are
> puzzling to me and
> I can't figure out how to compute a simple factor score (to use in a
> regression analysis).
>
> Could someone please point me in the right direction?

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