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Hi Owen I can't see why you could not get the regression values (invert X) .. maybe something strange happen with the df or something similar .. how may row/columns do you end up with? this could be the answer .. ?? Cyril > Hello, > > I'm having a problem running a flexible factorial with a large dataset. > we have 15 subjects, scanned on 3 occasions, with six resting perfusion > images per session (270 images in total). > i'm running a model with 3 factors > 1. subjects > 2. session > 3. scan > > the problem is that while i can get the model to run the contrast manager > won't accept any contrasts. I have changed the settings and found that > > 1. if i remove one subjects scans it runs fine (14subject*18scans) > 2. if i remove the subjects regressors (main effect) from the flexible > factorial design matrix it runs fine. > 3. if i run a 18 cell full factorial it runs fine > the only problem is when i run 15 subjects with 18 scans in a flexible > factorial. > i thought perhaps that there was a total limit on the number of columns in > the flexible factorial DM, however if i use only 14 subjects but include an > ANCOVA column (global mean) the total number of columns is the same as with > 15 subjects but the model, and contrast definition, runs fine. > > does anyone know if there are any potential limits either on the number of > columns, total number of images, or anything that could explain this problem? > > cheers > Owen > > Dr Owen O'Daly > Post-Doctoral Researcher > Centre for Neuroimaging Sciences > Institute of Psychiatry, KCL > De Crespigny Park > Denmark Hill > SE5 8AF > Tel: 020 3228 3047 > > -- Dr Cyril Pernet, fMRI Lead Researcher SINAPSE SFC Brain Imaging Research Center Division of Clinical Neurosciences University of Edinburgh Western General Hospital Crewe Road Edinburgh EH4 2XU Scotland, UK [log in to unmask] tel: +44(0)1315373661 http://www.sbirc.ed.ac.uk/cyril http://www.dcn.ed.ac.uk/bic/sinapse/sinapse.asp -- The University of Edinburgh is a charitable body, registered in Scotland, with registration number SC005336.