A suggestion, if it isn't too much trouble. Could you add a column for mass? Christine On Mon, 2012-07-09 at 16:11 -0600, Stephen Skory wrote: > Ooops, try this: > > halos = LoadTextHaloes(pf, "list.txt", {'x':0, 'y':1, 'z':2, 'r':3}, > comment = ";") > > > >