If your plot is for instance:
figure(1)
surf(X, Y, Z)
where all are matrices, convert ‘Z’ to a vector and then take the max:
Zmax = max(Z(:));
If you want to know where the maximum occurs, this will give you the indices:
[Zmax,Idx] = max(Z(:));
[ZmaxRow,ZmaxCol] = ind2sub(size(Z), Idx);
