Matrix

The matrix flag indicates that the data are stored in matrix format. In its present implementation the z-values are read in a row at a time, i. e.,
     z11 z12 z13 z14 ...
     z21 z22 z23 z24 ...
     z31 z32 z33 z34 ...
and so forth. The row and column indices are used for the x- and y-values. used as x, y, and z.