def _update_variance_in_window(self):
self._covariance_in_window = sum([(xj - self._mean_x_in_window) *<EOL>(yj - self._mean_y_in_window)<EOL>for xj, yj in zip(self._x_in_window, self._y_in_window)])<EOL>self._variance_in_window = sum([(xj - self._mean_x_in_window) ** <NUM_LIT:2> for xj<EOL>in self._x_in_window])<EOL>
Compute variance and covariance in window using all values in window (slow).

See Also
--------
_add_observation_to_variances : fast update for single observation addition
_remove_observation_from_variances : fast update for single observation removal