def castroData_from_ipix(self, ipix, colwise=False):
        """ Build a CastroData object for a particular pixel """
        # pix = utils.skydir_to_pix
        if colwise:
            ipix = self._tsmap.ipix_swap_axes(ipix, colwise)
        norm_d = self._norm_vals[ipix]
        nll_d = self._nll_vals[ipix]
        return CastroData(norm_d, nll_d, self._refSpec, self._norm_type)
Build a CastroData object for a particular pixel