Hello,

I'm trying to run selxavg3-sess with FS v4.5 for an FIR analysis where each trial is modeled as a separate condition. The command works smoothly for the majority of subjects, but for 2 different subjects, it exits with the following error:

Saving X matrix to /home/sam/fMRIDATA/samstudies/SoCo/SoCo10/bold/Logit/Xtmp.mat XCond = 12220.6 (normalized) ERROR: design is ill-conditioned

...

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ERROR: fast_selxavg3() failed\n

details: I do not definite any contrasts, as I'm only running this command to generate trial specific betas for a separate analysis. Each trial lasts 18 seconds, followed by 4 seconds of fixation. Here is what part of a paradigm file looks like (the paradigm files are identical for all subjects):

4 1 18 1 22 0 4 1 26 2 18 1 44 0 4 1 48 3 18 1 66 0 4 1 70 4 18 1 88 0 4 1 92 5 18 1 110 0 4 1 114 6 18 1 132 0 4 1 136 7 18 1 154 0 4 1

here are the analysis.cfg and .info files: analysis analysis_name TR 2 fsd bold funcstem fmcsm4 tpexclude parname FIR_logit.par designtype event-related nconditions 96

-timewindow 20 -prestim 2 -acfbins 10 -fix-acf -noautostimdur -no-fsv3-st2fir -no-fsv3-whiten -polyfit 2 -TER 2 -nskip 0 -fwhm 0 -extreg mcextreg -nextreg 3 -rescale 1000

the command which throws the error: selxavg3-sess -analysis analysis_name -s subject_name

The strange part for me is that this only seems to be a problem with a couple subjects, despite the fact all the paradigm files are identical. After looking through the mailing archive, I tried playing around with the prestim window, but even it if is = 0, there is 1 subject that exits with an error when I run selxavg3-sess. Do you know what might be going on?

Any guidance would be appreciated.

Thanks, Sam