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Dear Freesurfer developpers,
I posted a while back asking how to control for scanner site in a multi-centre study. I think I now understand the formatting to do so for a DOSS model, but was wondering how this would look for a DODS model. There are 6 scanner sites and I also want to control for age and sex. However, there are no females in 3 of the sites. I tried to create the contrast for this but got the following error: ERROR: matrix is ill-conditioned or badly scaled, condno = 1e+08 -------------------------------- Possible problem with experimental design: Check for duplicate entries and/or lack of range of continuous variables within a class. If you seek help with this problem, make sure to send: 1. Your command line: mri_glmfit.bin --y rh.5.lgi.centre.mgh --fsgd FSGD_centre.txt dods --glmdir rh.5.lgi.centre.glmdir --surf fsaverage rh --C H-NH_centre.dods.txt 2. The FSGD file (if using one) 3. And the design matrix above Attempting to diagnose further SumSq: Min=1.000000 (col 4), Max=183.117447 (col 31) The scale is much different between columns 4 and 31, you may want to normalize by subtracting the mean and dividing by the standard deviation.
My contrast was 1 -1 -1 -1 -1 -1 -1 -1 -1 0.75 0.75 0.75 0.75 0.75 0.75 0.75 0.75 0.75 0.75 0.75 0.75 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 and FSGD attached (does not include full list of subjects).
Thanks very much, Colleen