code: def _normalised_numpy(self):
          
          dx = (self.screen.width / float(len(self.points)))
          oy = (self.screen.height)
          points = np.array(self.points) - self.minimum
          points = points * 4.0 / self.extents * self.size.y
          for x, y in enumerate(points):
              yield Point((
                  dx * x,
                  min(oy, oy - y),
              ))
docs: Normalised data points using numpy.