There is not an error, per se. An ill-conditioned matrix means that your design matrix has two or more columns that are too similar. Check your continuous variables to see whether they are similar (eg, age and education level). Finally, it is difficult to diagnose the problem without more info, try looking at surfer.nmr.mgh.harvard.edu/fswiki/BugReporting for better ways to report problems.

doug

Juergen Haenggi wrote:

Dear Freesurfer experts

We have two problems with FS statistics.

One problem occurred when using mri_glmfit:

Matrix condition is 11198.7 ERROR: matrix is ill-conditioned or badly scaled, condno = 11198.7 Possible problem with experimental design: Check for duplicate entries and/or lack of range of continuous variables within a class.

I inspected the FSGD file but did not find any error! There was a suggestion in the FS archives to look at the design matrix for significant off-diagonal values but the design matrix (X.mat) was not produced Any idea where the problem is?

In another contrast the sig.mgh file produced huge values and the whole brain is colored yellow (see attachment). What happens here?

Thanks a lot in advance Best regards Juergen

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Juergen Haenggi Ph.D. (Dr. des.) Division of Neuropsychology Institute of Psychology University of Zurich Binzmuehlestrasse 14, PO Box 25 8050 Zurich, Switzerland 0041 44 635 73 97 (phone office) 0041 76 445 86 84 (phone mobile) 0041 44 635 74 09 (fax office) BIN 4.D.04 (office room number) j.haenggi@psychologie.uzh.ch (email) http://www.psychologie.uzh.ch/neuropsy/ (website) http://www.juergenhaenggi.ch (private website)

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