Hi Stan,
I do not understand your point about Clone! Why do you call this function?
If you want to have a correct error calculation in the resulting
histogram, at least one of the operand histograms (in your case em8 or all
must have Sumw2.
Before Dividing, do
all->Sumw2(); em8->Sumw2();
see: http://root.cern.ch/root/htmldoc/TH1.html#TH1:Divide
Rene Brun
On Thu, 31 Jan 2002, Stanley Forrester wrote:
> I'm having some trouble with displaying error bars on an efficency plot.
> Can anyone tell me what I'm doing wrong? Also why does one need to call
> Clone before "dividing."
>
> The data in the histo "em8" is a subset of the data in histo "all" so I'm
> trying to use the binomial error method. The resulting histogram
> displays error bars equal to the value the contents of the bin.
>
> TH1F* all = CEM8Track5Validation_All_electronEt;
> TH1F* em8 = CEM8Track5Validation_Electron_Central_8_v_electronEt;
> TH1F *e_ratioEt =
> (TH1F*)CEM8Track5Validation_Electron_Central_8_v_electronEt
> ->Clone();
> e_ratioEt->Divide(em8, all,1,1, "B");
> all->Draw();
> em8->Draw();
> e_ratioEt->Draw("e");
>
> ________________________________________________________________
> Stanley S. Forrester
> sforrest@lifshitz.ucdavis.edu
>
> I like pigs. Dogs look up to us. Cats look down on us.
> Pigs treat us as equals.
> Sir Winston Churchill
>
>
>
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