Thank you so much for your answer! Now I meet another problem. Just as your see, the C in some classes (e.g., A1B1 and A2B1) is all zeros. When I run the mri_glm. Some error information was shown. I listed them below.
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. How can I deal to this error? Thanks again! Xiaochu Zhang PhD Visiting Research Fellow Neuroimaging Research Branch National Institute on Drug Abuse - IRP Biomedical Research Center 251 Bayview Blvd. Suite 200 (NIDA) Baltimore MD 21224 Tel: 443-740-2619 -----Original Message----- From: Douglas N Greve [mailto:gr...@nmr.mgh.harvard.edu] Sent: Wednesday, July 15, 2009 12:31 PM To: Zhang, Xiaochu (NIH/NIDA) [F] Cc: freesurfer@nmr.mgh.harvard.edu Subject: Re: [Freesurfer] ANOVA and co-variable yes, that is correct. Make sure to handle the mean/offset of C in a rational way. The simple, though somewhat incorrect, way is to simply demean C. Better to pick a fixed value of C to test it at. If this is what you do, let's say you test at C=2, then your contrast would be: 0.5 -0.5 -0.5 0.5 2 2 2 2 ie, you would just replace the 0s in the C-columns with 2. doug Zhang, Xiaochu (NIH/NIDA) [F] wrote: > > Hi Freesurfer experts, > I want to do a group ANOVA analysis with one co-variable. I have read > the corresponding wiki but still have some problems. I need your help. > > I have 4 group subjects (A1B1, A1B2, A2B1, A2B2) and one co-vaiable (C). > I want to get the interaction between A and B. However, because C is > different in different groups, I need to rule out the influence from C > in my ANOVA analysis. > So the model is A*B+C. > > The fsgd file is > GroupDescriptorFile 1 > Title SK-SZ > Class A1B1 > Class A1B2 > Class A2B1 > Class A2B2 > Variable C > Input S1 A1B1 0.0 > Input S2 A1B2 2.0 > Input S3 A2B1 0.0 > Input S4 A2B2 3.0 > > The mtx file is > 0.5 -0.5 -0.5 0.5 0 0 0 0 > > Is it correct? > Thanks a lot! > > Xiaochu Zhang PhD > > Visiting Research Fellow > > Neuroimaging Research Branch > > National Institute on Drug Abuse - IRP > > Biomedical Research Center > > 251 Bayview Blvd. > > Suite 200 (NIDA) > > Baltimore MD > > 21224 > > Tel: 443-740-2619 > > > ---------------------------------------------------------------------- > -- > > _______________________________________________ > 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 In order to help us help you, please follow the steps in: surfer.nmr.mgh.harvard.edu/fswiki/BugReporting _______________________________________________ Freesurfer mailing list Freesurfer@nmr.mgh.harvard.edu https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer
