def sum(self, axis):
        """Sums all data along axis, returns d-1 dimensional histogram"""
        axis = self.get_axis_number(axis)
        if self.dimensions == 2:
            new_hist = Hist1d
        else:
            new_hist = Histdd
        return new_hist.from_histogram(np.sum(self.histogram, axis=axis),
                                       bin_edges=itemgetter(*self.other_axes(axis))(self.bin_edges),
                                       axis_names=self.axis_names_without(axis))