Hello

I have two conditions and have calculated a t-map from 3dttrest++ for each. I now want to create a mask that shows which voxels are active for both conditions. I used the following command based on 3dcalcs help file.

3dcalc -a 'A' -b 'B' -expr '3*step(a-3)'+3*step(b-3)' -prefix common_mask

A and B are the results from my 3dttest++. I thresholded it, and only wanted voxels with a t-value of 3. The resulting common_mask looked right at first, but I'm noticing that there are voxels showing in the mask that are not active in condition A.

I'm slightly now confused on what the 3*step does. At first, I thought it was how I tell 3dcalc to only calculate voxels in A and B only.

Thank you for your time.