0 1 1 will just be the mean of the slopes of var1 and var2. Looks like you want 0 1 -1 to look for the interaction.
doug
Victoria Williams wrote:
Hello,
I apologize if this is a very simple question, but how would you set up a contrast matrix to look at the interaction of 2 variables on a measure? For example, my fsgd file contains:
class=1 variables=2 Input Subjid class var1 var2
When I tried using a contrast of 0_1_1 the significance map looks very similar to the glm run only containing var1 (contrast_0_1). I thought 0_1_1 was correct, but now I'm not so sure and would like to double check. What I am interested in is how the interaction of var1 and var2 is correlated with the brain measure per voxel. Is this possible with mri_glmfit?
I've checked the tutorials and scoured the internet as not to ask any silly questions, but I'm having trouble finding anything helpful.
Thanks in advance! Tori _______________________________________________ Freesurfer mailing list Freesurfer@nmr.mgh.harvard.edu https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer