Dear friends, I have two TH1F* objects h1 and h2 and would like to get the ratio of the two histos into a third one with the correct error calculation (i.e. Sumw2() option). If I do : TH1F h3=(*h1); h3.Sumw2(); h3.Divide(h1,h2,1,1); h3.Draw(); I get the correct result (i.e. h3 drawn with correct error bars). However, now I would like to use the convenient 'histo operators' and do : TH1F h3=(*h1)/(*h2); h3.Draw(); But now h3 is drawn as a histo without error bars, giving me the impression that the Sumw2() option was not used. When I do h3.Draw("e1p") I see that indeed the errors are incorrect. Q : How can I achieve correct error calculation using the 'histo operators' ? Note : A default won't work, since sometimes in h3=(*h1)+(*h2) one would like to add without Sumw2() and sometimes with Sumw2() set. Another point is the following : I would like to have h3 also defined as TH1F*, but clearly TH1F* h3=(*h1)/(*h2) will fail. How to achieve this ? Cheers, Nick. *----------------------------------------------------------------------* Dr. Nick van Eijndhoven Department of Subatomic Physics email : nick@fys.ruu.nl Utrecht University / NIKHEF tel. +31-30-2532331 (direct) P.O. Box 80.000 tel. +31-30-2531492 (secr.) NL-3508 TA Utrecht fax. +31-30-2518689 The Netherlands WWW : http://www.fys.ruu.nl/~nick Office : Ornstein lab. 172 ---------------------------------------------------------------------- tel. +41-22-7679751 (direct) CERN PPE Division / ALICE exp. tel. +41-22-7675857 (secr.) CH-1211 Geneva 23 fax. +41-22-7679480 Switzerland CERN beep : 13+7294 Office : B 160 1-012 *----------------------------------------------------------------------*
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