[R] How to combine to PCAs

[Stefan Koenig]

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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