Dear Freesurfer team,

I'm running a group analysis where I'd like to compare myelination between two groups regressing out cortical thickness, age and sex.

My FSGD file is:

GroupDescriptorFile 1

Title Func

Class HC

Class CMT

Variables Age gender

Input fs_VF HC 46 Female

Input fs_RF HC 24 Female

.......

My group.diff.mtx is:

1 -1 0 0 0 0 0

My command line:

mri_glmfit.bin --y rh.t1t2ratio_30_fmed_3sm_decurv.fsavg.mgh --fsgd age_gender.fsgd --pvr rh.thickness_30.fsavg.mgh --C group.diff.mtx --surf fsaverage rh --cortex --glmdir rh_allbrain_t1t2_group_thickness_age_gender.glmdir

But unfortunately I get this wrong message:

RROR: 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:

2. The FSGD file (if using one)

3. And the design matrix above

Attempting to diagnose further

SumSq: Min=0.000000 (col 5), Max=146.140350 (col 3)

The scale is much different between columns 5 and 3, you may want to

normalize by subtracting the mean and dividing by the standard deviation.

Column 5, all values are 0

Column 6, all values are 0

Columns 5 and 6 are the same

Can you please help me?

Thank you very much

Raf