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