Return true if only one element in matrix is nonzero

How do I find out if my matrix contains only one non-zero element and return true, if not false.

Such that

0 0 0
0 0 0
0 0 0

should return FALSE(all element are zero)

0 0 0
0 0 1
0 0 1

should return FALSE(more than one element is non-zero)

And finally;

0 0 0
0 0 0
0 0 1

should return TRUE

I could use a for loop but i was wondering if there is any function that can do that

Answer 1

[Guillaume]

 nnz(yourmatrix) == 1