It's not exactly trivial. I like to add a non-estimable constraint, which in this case is a row of 1's and a 0 for the value of the corresponding response. The coefficients are not unique, but the t-tests are correct, as are the multiple comparisons.
christoph wrote: > 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 -- Bob Wheeler --- http://www.bobwheeler.com/ ECHIP, Inc. --- Randomness comes in bunches . . ================================================================= Instructions for joining and leaving this list, remarks about the problem of INAPPROPRIATE MESSAGES, and archives are available at: . http://jse.stat.ncsu.edu/ . =================================================================
