function func_surf(func_name,xarray,yarray)
zarray = xarray * yarray'

i=1;
for x = xarray
    j=1;
    for y = yarray
        zarray(i,j) = feval(func_name,[x,y]);
        j = j+1;
    end
    i=i+1;
end

surf(xarray,yarray,log10(zarray))