def _update_mean_in_window(self):
self._mean_x_in_window = numpy.mean(self._x_in_window)<EOL>self._mean_y_in_window = numpy.mean(self._y_in_window)<EOL>
Compute mean in window the slow way. useful for first step.

Considers all values in window

See Also
--------
_add_observation_to_means : fast update of mean for single observation addition
_remove_observation_from_means : fast update of mean for single observation removal