def data_response(self):
        """
        returns the 1d array of the data element that is fitted for (including masking)

        :return: 1d numpy array
        """
        d = []
        for i in range(self._num_bands):
            if self._compute_bool[i] is True:
                d_i = self._imageModel_list[i].data_response
                if d == []:
                    d = d_i
                else:
                    d = np.append(d, d_i)
        return d