When split-file processing is in effect, the first
variables in the matrix file will be split variables, followed by ROWTYPE_, VARNAME_, and the variables used to form the correlation matrix.
A full set of matrix materials is written for each
subgroup defined by the split variables.
A split variable cannot have the same name as any
other variable written to the matrix data file.
If split-file processing is in effect when a matrix
is written, the same split-file specifications must be in effect when
that matrix is read by another procedure.