Take a look at the newish programs 3dmaskSVD and 3dLocalSVD
[
afni.nimh.nih.gov]
[
afni.nimh.nih.gov]
You can also use 1dSVD for 1D files as done for structural equation modeling (the script is available here). You end up using the first column of number that make up the left vector.
[
afni.nimh.nih.gov]