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st: how drawing confidence ellipses in a pca?

From   Luigi Curini <>
Subject   st: how drawing confidence ellipses in a pca?
Date   Tue, 06 Mar 2007 14:56:17 +0100

Dear all,
I'd like to have your advice about a puzzle I have. I need to use a
principal component analysis (PCA) to estimate the positions of parties
within a 2-dimensional space. However, to complete the analysis, I'd like to
visualize into the graph of this 2-dimensional (political) world not only
the political parties' means, but also the uncertainty in their mean
positions, drawing confidence ellipses around them (or at least, drawing
confidence segments centered on each mean point along the two dimensions).
This is because parties have widely different standard deviations along the
two dimensions. How to do it?
Thanx for any advice,

Dr. Luigi Curini
UniversitÓ degli Studi di Milano
FacoltÓ di Scienze Politiche
Dipartimento di Studi Sociali e Politici
Via Conservatorio, 7
I - 20122 Milano
Tel. +39 02 50318831
Fax  +39 02 50318840

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