def supplement(self,coordsys='gal'):
        """ Add some supplemental columns """
        from ugali.utils.projector import gal2cel, gal2cel_angle
        from ugali.utils.projector import cel2gal, cel2gal_angle

        coordsys = coordsys.lower()
        kwargs = dict(usemask=False, asrecarray=True)
        out = copy.deepcopy(self)

        if ('lon' in out.names) and ('lat' in out.names):
            # Ignore entries that are all zero
            zeros = np.all(self.ndarray==0,axis=1)

            if coordsys == 'gal':
                ra,dec = gal2cel(out.lon,out.lat)
                glon,glat = out.lon,out.lat
            else:
                ra,dec = out.lon,out.lat
                glon,glat = cel2gal(out.lon,out.lat)

            ra[zeros] = 0; dec[zeros] = 0
            glon[zeros] = 0; glat[zeros] = 0

            names = ['ra','dec','glon','glat']
            arrs = [ra,dec,glon,glat]
            out = mlab.rec_append_fields(out,names,arrs).view(Samples)
            #out = recfuncs.append_fields(out,names,arrs,**kwargs).view(Samples)

            if 'position_angle' in out.names:
                if coordsys == 'gal':
                    pa_gal = out.position_angle
                    pa_cel = gal2cel_angle(out.lon,out.lat,out.position_angle)
                    pa_cel = pa_cel - 180.*(pa_cel > 180.)
                else:
                    pa_gal = cel2gal_angle(out.lon,out.lat,out.position_angle)
                    pa_cel = out.position_angle
                    pa_gal = pa_gal - 180.*(pa_gal > 180.)
                    
                pa_gal[zeros] = 0; pa_cel[zeros] = 0
                names = ['position_angle_gal','position_angle_cel']
                arrs = [pa_gal,pa_cel]
                out = recfuncs.append_fields(out,names,arrs,**kwargs).view(Samples)
        
        return out
Add some supplemental columns