External Email - Use Caution I thought that I could not remove the class since this would mean that the contrast positive and negative values would no longer add up to 0. For instance if I remove only class "patient_centre2_female", then my contrast would have 11 (-1) and 12 (1) as opposed to 12 and 12. Could you please clarify?
Thanks again, Colleen -------- Original Message -------- Subject: Re: [Freesurfer] FSGD design for multi-centre study Date: 2018-04-20 11:19 From: "C.P.E. Rollins" <cp...@cam.ac.uk> To: Freesurfer <freesurfer@nmr.mgh.harvard.edu> Thanks a lot for the explanation. The issue is that I don't think Freesurfer will run a design for which there are no subjects for a given class. So if I keep the classes (24 classes since 6 centres x 2 gender x 2 groups (patient vs. control), and have the contrast with 12 (-1) and 12 (1), -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 1 1 1 1 1 1 1 1 1 1 1 1 0 I get the error: -------------------------------- 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. I'm assuming this is because there are no participants in, for example, patient_centre2_female Is there any way to get around this issue, or should I remove those centres from my analysis (since I can't only remove "patient_centre2_female", as this would make the contrast unbalanced (positives and negatives would not add to the same number). I hope this was clear but please let me know if it was not. Thanks again, Colleen _______________________________________________ Freesurfer mailing list Freesurfer@nmr.mgh.harvard.edu https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer The information in this e-mail is intended only for the person to whom it is addressed. If you believe this e-mail was sent to you in error and the e-mail contains patient information, please contact the Partners Compliance HelpLine at http://www.partners.org/complianceline . If the e-mail was sent to you in error but does not contain patient information, please contact the sender and properly dispose of the e-mail.
