finding state transition matrix-regd.

hello every one i have a matrix A as syms t A=[-1 0;exp(-3*t) 0] i tried to find the state transition matrix by using

function [phi] = statetrans(A) t = sym('t'); phi = expm(A * t); end But came up with an error showing

??? function [phi] = statetrans(A) ??? Undefined function or method 'statetrans' for input arguments of type 'sym'. | Error: Function definitions are not permitted in this context

Then i replaced t with r in matrix A

But i didnot get the result but showed an error of

??? function [phi] = statetrans(A)

    |
Error: Function definitions are not permitted in this context

Please help me guys..........