Dear gPPI experts,
 
I am trying to run a gPPI on a linear trend (like -1.5 -0.5 0.5 1.5), but I seem to fail to implement this correctly in the toolbox. I tried two different approaches:
 
1)
P.Contrasts(1).left={[0 0 0 0 0 0 0 0 0 0 0 0 0 -0.5 0.5 1.5 0 0 0 -1.5]};
P.Contrasts(1).right={};
P.Contrasts(1).STAT='T';
P.Contrasts(1).Weighted=0;
P.Contrasts(1).MinEvents=5;
P.Contrasts(1).name='PPI Emotion increase'; 
 
2)
P.Contrasts(1).left={};
P.Contrasts(1).right={};
P.Contrasts(1).c={[0 0 0 0 0 0 0 0 0 0 0 0 0 -0.5 0.5 1.5 0 0 0 -1.5]};
P.Contrasts(1).STAT='T';
P.Contrasts(1).Weighted=0;
P.Contrasts(1).MinEvents=5;
P.Contrasts(1).name='PPI Emotion increase'; 
 
 
Neither one seems to work as the script and Matlab are freezing while other contrasts run fine...
Is it generally possible to run gPPI on such a contrast? And if yes, what would be the correct implementation?
 
Thank you very much for you help!

Kevin

Hi Kevin,

That contrast should work assuming that the columns are correctly aligned. The only thing that needs to be changed is to remove the {} around the contrast. For example, P.Contrasts(1).c=[0 0 0 0 0 0 0 0 0 0 0 0 0 -0.5 0.5 1.5 0 0 0 -1.5];

If this doesn't work, please send me the SPM.mat file and I can try and troubleshoot further.

Best,
Donald