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st: AW: vce matrix manipulation in pca

From   Sheela Athreya <>
Subject   st: AW: vce matrix manipulation in pca
Date   Sat, 7 Aug 2010 12:09:20 -0500


Thank you for the advice. It's very helpful.  I used "_00001" because it was one of two matrices in my pulldown menu when I used the "define matrix" command window, after running the PCA.  I figured it was temporary and hence I couldn't really manipulate it.

Is there a way to compute PC scores based on a new data set but using a pre-defined vce matrix? (The C matrix below that you helped me define)

Many thanks,

> Date: Fri, 6 Aug 2010 09:44:42 +0200
> From: "Martin Weiss" <>
> Subject: st: AW: vce matrix manipulation before and after pca
> <> 
> Technically, you can do it like this, but I am not sure whether the result
> is meaningful in any way:
> *************
> sysuse auto, clear
> pca trunk weight length headroom if foreign, vce(normal)
> mat A=e(V)
> pca trunk weight length headroom if !foreign, vce(normal)
> mat B=e(V)
> mat C=(A+B)/2
> mat l C
> *************
> Where did you get the idea to use "__000001"? These are temporary objects
> which you cannot access the way you tried to...
> Martin
Sheela Athreya, Ph.D.
Department of Anthropology
Texas A&M University
College Station, TX  77843

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