Array from MAT-file
Pointer to a newly allocated mxArray structure representing the mxArray named by name from the MAT-file pointed to by mfp.
matGetVariable returns NULL in C (0 in Fortran) if the attempt to return the mxArray named by name fails.
This routine allows you to copy an mxArray out of a MAT-file.
Use mxDestroyArray to destroy the mxArray created by this routine when you are finished with it.