Re: [R] How to combine to PCAs

From: Ravi Varadhan <RVaradhan_at_jhmi.edu>
Date: Thu, 05 Jun 2008 09:40:35 -0400

Let V = (v11, v12, ..., v1n, v21, v22, ..., v2n) be the matrix of data with 2*n columns. Now, you simply do PCA on this data matrix. See the following paper, which has a related example:

Gabriel, K. R. and Odoroff, C. L. (1990). Biplots in biomedical research. Statistics in Medicine, 9, 469-485.

Ravi.

-----Original Message-----
From: r-help-bounces_at_r-project.org [mailto:r-help-bounces_at_r-project.org] On Behalf Of Stefan Koenig
Sent: Thursday, June 05, 2008 4:47 AM
To: r-help_at_r-project.org
Subject: [R] How to combine to PCAs

Dear all:

Subjects were measured two times (t1 and t2) on different variables (v1 ... vn).
Between t1 and t2 there was an experimental manipulation. I computed two PCAs for time-points t1 and t2.

Is it possible to combine both PCAs in order to get only one set of eigenvectors? Due to the experimental manipulation measurement values on time points t1 and t2 changed for each subject.

Many thanks
Stefan

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Received on Thu 05 Jun 2008 - 15:43:31 GMT

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