Creates model matrices/vectors

        Returns
        ----------
        None (changes model attributes)

def _create_model_matrices(self):
        """ Creates model matrices/vectors

        Returns
        ----------
        None (changes model attributes)
        """

        self.model_Y = np.array(self.data[self.max_lag:self.data.shape[0]])
        self.model_scores = np.zeros(self.model_Y.shape[0])