Hi Freesurfer Experts,
I am hoping someone can help me solve this error I'm experiencing while
conducting a simple qdec analysis. I have 4 subjects (3 vs 1) that I am trying
to analyze for volume differences using a demeaned ICV as a nuisance factor
(see attached fsgd file - note I changed the .dat extension as my email server
didn't like the dat format).
However, I am getting this error:
Normalized matrix condition is 1e+08
Design matrix ------------------
0.000 1.000 0.000 -28915.199;
0.000 1.000 0.000 194736.703;
0.000 1.000 0.000 -184311.000;
1.000 0.000 18489.000 0.000;
--------------------------------
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 --y
/media/seagate_external_/freesurfer_subjects/qdec/Untitled/y.mgh --fsgd
/media/seagate_external_/freesurfer_subjects/qdec/Untitled/qdec.fsgd dods
--glmdir /media/seagate_external_/freesurfer_subjects/qdec/Untitled --surf
fsaverage rh --label
/media/seagate_external_/freesurfer_subjects/fsaverage/label/rh.aparc.label --C
/media/seagate_external_/freesurfer_subjects/qdec/Untitled/contrasts/rh-Avg-Intercept-volume.mat
--C
/media/seagate_external_/freesurfer_subjects/qdec/Untitled/contrasts/rh-Avg-volume-ICV-Cor.mat
--C
/media/seagate_external_/freesurfer_subjects/qdec/Untitled/contrasts/rh-Diff-CVI-PVL-Intercept-volume.mat
--C
/media/seagate_external_/freesurfer_subjects/qdec/Untitled/contrasts/rh-Diff-CVI-PVL-Cor-volume-ICV.mat
2. The FSGD file (if using one)
3. And the design matrix above
Error in Analyze: command failed: mri_glmfit --y
/media/seagate_external_/freesurfer_subjects/qdec/Untitled/y.mgh --fsgd
/media/seagate_external_/freesurfer_subjects/qdec/Untitled/qdec.fsgd dods
--glmdir /media/seagate_external_/freesurfer_subjects/qdec/Untitled --surf
fsaverage rh --label
/media/seagate_external_/freesurfer_subjects/fsaverage/label/rh.aparc.label --C
/media/seagate_external_/freesurfer_subjects/qdec/Untitled/contrasts/rh-Avg-Intercept-volume.mat
--C
/media/seagate_external_/freesurfer_subjects/qdec/Untitled/contrasts/rh-Avg-volume-ICV-Cor.mat
--C
/media/seagate_external_/freesurfer_subjects/qdec/Untitled/contrasts/rh-Diff-CVI-PVL-Intercept-volume.mat
--C
/media/seagate_external_/freesurfer_subjects/qdec/Untitled/contrasts/rh-Diff-CVI-PVL-Cor-volume-ICV.mat
There are no duplicate entries. I have done this same analysis with a higher
number of subjects without problems. I have also tried using the inbuilt qdec
ICV (which is not demeaned) and got the same error. Could this be a problem
with the small subject count? If so, is there any way to remedy it?
Thank you!
Gabriella
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fsid group ICV
FLS_08212014 PVL -28915.2
MWB_07252014 PVL 194736.7
MMJ_06142013 PVL -184311
FEK_11172014 CVI 18489
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