  :: Put a different way, the 1 on the x axis is the same as the 1 on the y axis, but (1,0) is not the same as (0,1). You can certainly take the coordinates (x,f(x)), and then the function (f(y),y) and get different points, but you can't take the function f(x) and the function f(y) and get different values. ᛭   