compositional data: percent values sum up to 1

again, under another subject:
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 a perfect linear relationship 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

Christoph Lehmann <christoph.lehmann at gmx.ch>