def METHOD_NAME(self, ascii_data_file=None):
    if self.ascii_data_file is None:
        self._read_header()
    asciidata = np.loadtxt(
        op.join(
            self.workdir,
            self.ascii_data_file),
        comments='*')
    self.grid_xyz = [
        asciidata[
            :,
            i].reshape(
            *
            self.ncells[
                ::-
                1]).transpose(
                2,
                1,
            0) for i in range(3)]
    self.resistivity = asciidata[:, 3].reshape(
        *self.ncells[::-1]).transpose(2, 1, 0)[:-1, :-1, :-1]