I have an fMRI scan file with activation values of voxels (voxels can be located by specific coordinates). Let's say v is the 72x72x33 matrix representing information from the scan file. I can easily find a single value for a given combination of coordinates. For instance, v(x1,y1,z1) would give me the value of the voxel at location (x1,y1,z1). However, the challenge is that I need to get the mean value of multiple voxels. Let's say A (3x250 matrix) represents all the voxel coordinates of interest (so there are 250 voxels total). Could you please tell me how to get the average value of all these 250 voxels from v?