isdag(biograph), problem with matrix input.

syms matrix;
matrx = eye([3, 3]);
matrix=input('input your matrix');
lookfor isdag;
isdag(matrix);

I inserted lookfor isdag, matlab worked longer, but at the end sadly am getting same error :

input your matrix[1 0 0;1 1 0;1 1 1]
graphisdag - tests for cycles in a directed graph.
??? Undefined function or method 'isdag' for input arguments of type 'double'.

Error in ==> Untitled at 5
isdag(matrix);