Hello,
I ran mris_preproc on 56 subjects and then graphed the concatenated image. I also read this image into matlab and did the averaging using matlab, and then graphed the resulting image. When I did this, the two average pictures were slightly different. I thought that mris_preproc just simply averages all the subjects into common space. I noticed that its vector in matlab keeps the thickness value for all vertex's for all 56 subjects. I want to have the matlab capability for some custom processing I am doing, but the discrepancy leads me to think that mris_preproc is not a simple average. Can anyone elucidate this for me? Thank you!
Matlab script. Only place I would suspect a wrong assumption is when I throw out the rest of the subjects at curv4=curv3(1,:,:,1) %Select your input thickness file path='/mnt/users/Jeff/fs/lc/HIV/pass2pics/416/diff/nc.rh.ave.mgh';
%Read the thickness file curv=MRIread(path);
%Select the volume attribute curv2=curv.vol;
%Create a duplicate thickness array for manipulation curv3=curv2;
%Get the number of concatanated subjects tmp=size(curv2); m=tmp(4) clear 'tmp'
%Sum each vertex for all your subjects for im=2:m for in=1:7 curv3(1,:,in,1)=curv3(1,:,in,1)+curv2(1,:,in,im); end end
%Select just the first frame curv4=curv3(1,:,:,1);
%Compute the average thickness curv.vol=curv4/m;
%Write to thickness file MRIwrite(curv,'nc.rh.ave1.tmp.mgh');
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