Christoph Lehmann
2003-May-29 20:07 UTC
[R] collinearity for relative data (percent values)
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