On 11/27/2015 08:42 PM, nellie wrote:
Hi expert, Thank you for your reply. I had read the example tables, but I'm still not sure how to alter them into my analysis.Can you help me to check the matrix I designed and point out my mistakes? Thanks in advence. 3 classes ( A / B / C group) and 4 variables (gender, age, education, and Moca test score).
Gender has to be specified as a group, so you will have 6 classes (A-male, A-female, etc)
group.diff.mtx 1 -1 0 0 0 0 0 0 0 0 0 0 0 0 0
This would only test the difference between A and B. If you wan to look for an effect of group, then you will need a 2nd row which is 1 0 -1 000 000 000 000
group-x-gender.mtx 0 0 0 1 -1 0 0 0 0 0 0 0 0 0 0 group-x-age.mtx 0 0 0 0 0 0 1 -1 0 0 0 0 0 0 0 group-x-education.mtx 0 0 0 0 0 0 0 0 0 1 -1 0 0 0 0 group-x-moca.mtx 0 0 0 0 0 0 0 0 0 0 0 0 1 -1 0
Same as above. You need a 2nd row to each of these
group-x-gender-x-age-x-education.mtx 0 0 0 1 -1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 -1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 -1 0 0 0 0 group-x-gender-x-age-x-education-x-moca.mtx 0 0 0 1 -1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 -1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 -1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 -1 0
These two will be easier when you get the other matrices sorted out
group.diff.mtx also can write as: 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0
This does not compute a group difference, it looks for any voxel where any group or combination of groups is different than 0
group-x-age.mtx aslo can write as: 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0
same as above
. Wishes, Li
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- Re: How to create a 3g4v matrix (Lee Tirrell)
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Hi Li,
You can find some example FSGD tables here, which you can alter to fit your analyses.
https://surfer.nmr.mgh.harvard.edu/fswiki/FsgdExamples
Best, Lee
On Sun, 22 Nov 2015, nellie wrote:
Hi Freesurfer Experts,
I?m a new user of Freesurfer, and I learn how to use this software mainly through Wiki. When I came to the step of using GLM to compare group differences, I was confused on the design of 3g4v matrix. In my study, there were 3 classes ( A / B / C group) and 4 concomitant?variables (gender, age, education, and Moca test score). It?s supposed to be 15 regressors in this design, but I don?t know how to use the numbers (like 1, -1, 0, 0.5, -0.5, etc.) to create a correct matrix. I wonder if you could provide a 3g4v matrix in detail for me. I?ll be grateful if you can help. I hope I?m not bothering you too much, and I?m looking for your reply.
Best wishes,
Li?
?
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