Doug,
Thanks for your reply. I recalculated the beta value and got the same results as the Matlab does, but be different from the mri_glmfit's. I can not figure out where the problem is. Details following: I use the command mri_glmfit --table lh.volume.txt --fsgd volume.gender.fsgd doss --C gender.diff.mtx --glmdir lh.vol.glmdir to finish regression analysis. and got the beta value ( beta1 = 1.9781e+03, beta2 = 2.0639e+03, beta3 = 110.9220, beta4 = 5.1964e-04 ) from beta.mgh file. Using X.mat file and the same dependent variable Y.mat as mri_glmfit's, I got totally different results in Matlab( beta1 = 5.19e+02, beta2 = 4.44e+02, beta3 = 90.32, beta4 = 0.0015 ). I don't know how it happened...
Hope for your reply. The data I used are all in the attachment.
Best Regrads,
Lijie Huang On Fri, Apr 29, 2011 at 9:45 PM, greve@nmr.mgh.harvard.edu wrote:
Lijie,
I don't know what the matlab regress() function does. mri_glmfit is just solving the GLM equation, which you can do easily in matlab:
beta = inv(X'*X)*X'*y;
try that and see if you get the same as mri_glmfit.
doug
Hi all,
I'm working on a group analysis using mri_glmfit. In analysis directory, I got a X.mat file which containing the matrix X
(
size 50x4 ) used to regress analysis, also the beta value from beta.mgh file. Strangely, I loaded the X.mat in Matlab and recalculated the beta using function regress in matlab, but got a different result from that of mri_glmfit. I don't know where the problem is, is there any difference in algorithm between mri_glmfit and matlab function regress( regress(Y,X) )? or I made some mistakes during the procedure. The X.mat file and the dependent variable Y.mat are in the attachment.
Thanks in advance
Lijie Huang _______________________________________________ Freesurfer mailing list Freesurfer@nmr.mgh.harvard.edu https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer
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