Re: Problems to draw a weighted sum of histograms (corrected message)

Could you send the shortest possible RUNNING script (and data file) reproducing the problem?

Rene Brun

Antonio Augusto Alves Junior wrote:
> Hi all,
>
> Please, can you help me?
> I am using the TH1::Add(const TH1* , Double_t ) to add two histograms.
> I build the histogram h = c1*h1 + c2*h2, doing this
>
> h->Reset();
> h->Add( h1, c1);
> h->Add(h2,c2);
>
> here the h, h1 and h2 are TH1F objects, then I draw the histogram
>
> h->Draw();
>
> The problem: in the generated graph, is still possible see
> contributions from h1 histogram when c1 is null!
> By other side, the histogram's parameters, like h->Integral(),
> h->GetEntries() etc, has the correct values.
>
> Some hint? Is it a bug in the Draw() method?
> The piece of code is below.
>
> Best regards
> Augusto
>
> vector.front()->chain->Draw(draw_opt, filter, "goff" );
> TH1F *h = (TH1F*) (gDirectory->Get( histo_name ))->Clone("h");
> h->Reset(); Int_t h_nr=0;
> for( ChainVector::const_iterator it_vector = vector.begin();
> it_vector != vector.end(); it_vector++ )
> {
> TString h_name("histo_");
> h_name += h_nr;
> h_nr++;
> (*it_vector)->chain->Draw(draw_opt, filter, "goff" );
> TH1F *h1 = (TH1F*)(gDirectory->Get( histo_name ) )
> h->Add(h1, (*it_vector)->weight );
> delete h1; }
> h->Draw();
>
Received on Tue Aug 26 2008 - 08:45:14 CEST