CIGAL Reference Manual, Chapter 3 (Functions): matrix
usage: matrix_varb = matrix(xdim,ydim)
MATRIX is used to allocate memory space to a matrix variable that was not allocated space when originally declared. You can also use MATRIX to change the dimensions (and allocate new memory space) for such a matrix variable. You cannot use MATRIX, however, to set or change the memory allocated to a variable if the dimensions of the variable were specified during its initial declaration.