[R] collinearity for relative data (percent values)
Christoph Lehmann
lehmann at puk.unibe.ch
Thu May 29 22:07:21 CEST 2003
sorry, maybe an all too trivial question. But we have power data from J
frequency spectra and to have the same range for the data of all our
subjects, we just transformed them into % values, pseudo-code:
power[i,j]=power[i,j]/sum(power[i,1:J])
of course, now we have perfect collinearity in our x design-matrix,
since all power-values for each subject sum up to 1.
How shall we solve this problem: just eliminate one column of x, or
introduce a restriction which says exactly that our power data sum up to
1 for each subject?
Thanks a lot
Christoph
--
Christoph Lehmann <lehmann at puk.unibe.ch>
University Hospital of Clinical Psychiatry
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