Hi Gerco,
You are obviously right.
Thanks for reporting this problem now fixed in the dev version.
Rene Brun
Gerco Onderwater wrote:
>
> Hi Rooters,
>
> When I was trying to calculate the NDF of my fitting function and compared
> it to the NDF returned by TF1::GetNDF(), I noticed that they were
> different. I traced this down to the following few lines in H_H1.cxx:
>
> if (Foption.W1) {
> if (cu == 0 && flag == 2) continue;
> eu = 1;
> } else {
> eu = hfit->GetBinError(bin);
> if (eu <= 0) continue;
> }
>
> in both H1FitChisquare and H1FitLikelihood. I can believe that such a
> check is needed for chisquare minimization, but it definitely doesn't
> belong in the likelyhood calculation!!!! Bins with zero counts also have
> an error of zero (by definition: sqrt(N)), but that is only relevant for
> minimization schemes based on the error!!
>
> This means that all fitting procedures using the log(l) minimization done
> so far are meaningless!
>
> Demo:
>
> TF1* f = new TF1("f","gaus",-10,10)
> f->SetParameters(100,0,1)
> TH1D* h = new TH1D("h","h",100,-10,10)
> h->Eval(f,"S")
> h->Fit("f","L")
> h->GetFunction("f")->GetNumberFitPoints()
>
> This will return 32 instead of the expected and correct 100.
>
> Please update this!!
>
> -- Gerco
>
> Dr. C.J.G. Onderwater
> Nuclear Physics Laboratory
> 312 Loomis Laboratory of Physics
> University of Illinois at Urbana-Champaign
> 1110 West Green Street
> Urbana, IL 61801-3080
> Phone : (217) 244-7363
> Fax : (217) 333-1215
> E-mail: onderwat@uiuc.edu
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