This function checks whether its first argument is a Maple matrix. A matrix is defined to be a two-dimensional array with indices starting at 1.

If the argument R is given, the function checks whether A is a matrix with entries from the domain R.

If the argument square is given, then the function also checks if A is a square matrix.

When the second or third syntax is used, it is essential to quote the word matrix in order to avoid confusion with the matrix function in the linalg package.

Note: The command matrix has been superseded by Matrix.