Hi Zhang, when reporting a bug or problem, please refer to the following
suggestions in terms of what information you should report:
surfer.nmr.mgh.harvard.edu/fswiki/BugReporting
thanks!
doug
Zhang, Xiaochu (NIH/NIDA) [F] wrote:
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
----------------------------------------------------------------------
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--
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
--
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
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