you cannot do this in QDEC. In fact, it is a tricky analysis to do properly. For each group you will need an offset regressor and an age regressor, but only the patient group will have a burden regressor. This cannot be done with an FSGD file either. You will have to create your own design matrix, then pass it to mri_glmfit with the --X flag. You can get part of the way with an FSGD file (or QDEC) if you remove the Burden factor. This will create a design matrix to which you can add a single column for Burden which takes the Burden value for patients but is 0 for controls.
doug On 12/05/2013 12:40 PM, Cat Chong wrote: > Dear FreeSurfer Experts, > We are trying to run a between group analysis (1 patient group 1 > control group) within qdec. We are interested in investigating > age-related thickness differences between groups. Our fixed factors > are ‘group’ and our continuous covariate is ‘age’. We would like to > control for other possibly confounding variables which should be > declared as “nuisance factors, is that correct? > Here is our problem. We like to put down “disease burden” (years > subject has had the disease) as our nuisance factor, since it is > likely possible that this has an effect on cortical thinning in our > disease group. Yet, when we run the model, qdec crashes. Is this > because the subjects in the control group have a “0” as disease burden? > Could you advise us on another way of controlling for disease burden? > Cheers, > Catherine > > > _______________________________________________ > Freesurfer mailing list > Freesurfer@nmr.mgh.harvard.edu > https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer -- Douglas N. Greve, Ph.D. MGH-NMR Center gr...@nmr.mgh.harvard.edu Phone Number: 617-724-2358 Fax: 617-726-7422 Bugs: surfer.nmr.mgh.harvard.edu/fswiki/BugReporting FileDrop: https://gate.nmr.mgh.harvard.edu/filedrop2 www.nmr.mgh.harvard.edu/facility/filedrop/index.html Outgoing: ftp://surfer.nmr.mgh.harvard.edu/transfer/outgoing/flat/greve/ _______________________________________________ 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.
