FX Graph can plot groups of points and join them together. Simply place a + sign between the points.
(3,5)+(3,6)+(4,5)+(5,5)+(5,4)+(3,4)+(2,3)+(2,0)+(1,0)+(1,3)+(-1,3)+(-1,0)+(-2,0)+(-2,3)+(-3,4)+(-5,2)+(-5,3)+(-3,5)+(3,5)
You can mix points and groups of points in the same function.