It means that you have an ill-conditioned design matrix. It is probably the case that your discrete or continuous variables are redundant or that you don't have members in all your classes.

doug

Toh Hock Wong wrote:

Hi to all, I have been having troubles with qdec and several error messages appear. The first message appeared when clicking 'analyze'. It doesn't matter if i use one or two discrete plus one or two continuos factors, i get the same error message. What does it mean by codno=1e+08?

/Creating output directory /Applications/freesurfer/subjects/qdec/lh_postcentral_thickness/

/Loading y from /Applications/freesurfer/subjects/qdec/lh_postcentral_thickness/y.mgh/

/Matrix condition is 1e+08/

/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./

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Another error message that appeared earlier when i include age, gender, diagnosis(epilepsy/nonepileptic) and ln_postcentral_thickness is as follow:

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/$Id: mri_glmfit.c,v 1.138.2.3 2008/08/27 13:33:05 greve Exp $///

/cwd /Applications/freesurfer///

/cmdline mri_glmfit --y /Applications/freesurfer/subjects/qdec/lh_postcentral_thickness/y.mgh --fsgd /Applications/freesurfer/subjects/qdec/lh_postcentral_thickness/qdec.fsgd dods --glmdir /Applications/freesurfer/subjects/qdec/lh_postcentral_thickness --surf fsaverage lh --label /Applications/freesurfer/subjects/fsaverage/label/lh.cortex.label --C /Applications/freesurfer/subjects/qdec/lh_postcentral_thickness/contrasts/lh-Avg-Intercept-thickness.mat --C /Applications/freesurfer/subjects/qdec/lh_postcentral_thickness/contrasts/lh-Avg-thickness-age-Cor.mat --C /Applications/freesurfer/subjects/qdec/lh_postcentral_thickness/contrasts/lh-Avg-thickness-lh_postcentral_thickness-Cor.mat --C /Applications/freesurfer/subjects/qdec/lh_postcentral_thickness/contrasts/lh-Diff-Male-Female-Intercept-thickness.mat --C /Applications/freesurfer/subjects/qdec/lh_postcentral_thickness/contrasts/lh-Diff-Male-Female-Cor-thickness-age.mat --C /Applications/freesurfer/subjects/qdec/lh_postcentral_thickness/contrasts/lh-Diff-Male-Female-Cor-thickness-lh_postcentral_thickness.mat --C /Applications/freesurfer/subjects/qdec/lh_postcentral_thickness/contrasts/lh-Diff-nonepileptic-epilepsy-Intercept-thickness.mat --C /Applications/freesurfer/subjects/qdec/lh_postcentral_thickness/contrasts/lh-Diff-nonepileptic-epilepsy-Cor-thickness-age.mat --C /Applications/freesurfer/subjects/qdec/lh_postcentral_thickness/contrasts/lh-Diff-nonepileptic-epilepsy-Cor-thickness-lh_postcentral_thickness.mat --C /Applications/freesurfer/subjects/qdec/lh_postcentral_thickness/contrasts/lh-X-gender-diagnosis-Intercept-thickness.mat --C /Applications/freesurfer/subjects/qdec/lh_postcentral_thicknesss/contrasts/lh-X-gender-diagnosis-Cor-thickness-age.mat --C /Applications/freesurfer/subjects/qdec/lh_postcentral_thickness/contrasts/lh-X-gender-diagnosis-Cor-thickness-lh_postcentral_thickness.mat /

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Can the above error occur because one of the two groups has only one subject (epilepsy and female). I have also attached fsgd1 generated by freesurfer as below:

/GroupDescriptorFile 1///

/Title lh_postcentral_thickness///

/MeasurementName thickness///

/Class genderMale-diagnosisnonepileptic///

/Class genderFemale-diagnosisnonepileptic///

/Class genderMale-diagnosisepilepsy///

/Class genderFemale-diagnosisepilepsy///

/Variables age lh_postcentral_thickness ///

/Input RCoward genderMale-diagnosisnonepileptic 11.000000 2.112000 ///

/Input SCoward genderFemale-diagnosisnonepileptic 13.000000 1.979000 ///

/Input JConigrave genderMale-diagnosisnonepileptic 10.000000 2.470000 ///

/Input AConigrave genderFemale-diagnosisnonepileptic 5.000000 2.268000 ///

/Input KBleasel genderFemale-diagnosisnonepileptic 9.000000 2.292000 ///

/Input MBleasel genderFemale-diagnosisnonepileptic 16.000000 2.181000 ///

/Input CMcintosh genderFemale-diagnosisnonepileptic 15.000000 2.107000 ///

/Input OJohanssen genderMale-diagnosisnonepileptic 6.000000 2.033000 ///

/Input MJohanssen genderFemale-diagnosisnonepileptic 6.000000 2.037000 ///

/Input GHerbert genderFemale-diagnosisnonepileptic 4.000000 2.209000 ///

/Input JRathmell genderMale-diagnosisnonepileptic 11.000000 2.287000 ///

/Input ARathmell genderMale-diagnosisnonepileptic 14.000000 2.223000 ///

/Input ZTucker genderFemale-diagnosisepilepsy 11.000000 2.415000 ///

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Your advice and tips will be most appreciated!

        Toh Wong  (Sydney, Australia)

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