Try demeaning your covariates. By demeaning, I mean to compute the mean across all subjects, then subtract the mean from all values (for each covariate).
doug
On 3/1/15 2:40 AM, Anders Hougaard wrote:
Dear all, I'm comparing cortical thickness of a group of patients to a group of controls. I want to regress out the effects of gender, age, disease severity and disease duration. For the controls, the last two parameters equals zero. When running mri_glmfit, i get ERROR: matrix is ill-conditioned or badly scaled, condno = 1e+08 See the design matrix attached. My contrasts are set as 1 -1 0 0 0 0 0 0 0 0 and -1 1 0 0 0 0 0 0 0 0 What should I do to improve this? All the best, Anders _______________________________________________ Freesurfer mailing list Freesurfer@nmr.mgh.harvard.edu https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer
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