Hi Miro,
just do:
ntuple->Draw("var1:var2>>histv1v2")
and you ll get a hist with name "histv1v2"
often it is useful that yourself decide on the parameters
of the histogram, in this case you construct a hist yourself
and give its name to ntuple->Draw
TH2F * h2 = new TH2F("hv1v2", "var2 vs var1", 100,-2,2, 100, -2, 2)
ntuple->Draw("var1:var2>>hv1v2")
Cheers
Otto
On Tue, 14 Nov 2000, Miroslav Helbich wrote:
>
> Hi,
>
> I have an NTuple and I want to do some fast analysis. When
> I do ntuple->Draw("variable") it draws a nice histogram. How can I get a
> copy of it? In the following macro I use a trick with cloning histogram
> htemp created by TNtuple::Draw. However, this is not working for 2D
> histograms. What is wrong? Is there any way to get a histogram from
> TNtuple::DrawClone() ?
>
> Regards,
>
> Miro
>
> I'm using version 25_03 for SuSe Linux
>
> Macro:
>
> {
> // first generate ntuple
> TNtuple *ntuple = new TNtuple("ntuple","ntuple","Ehit:yhit");
> Double_t Ehit,yhit;
> for (Int_t i=0;i<100;i++) {
> Ehit = gRandom->Gaus(10.,0.5);
> yhit= gRandom->Gaus(0.,0.7);
> ntuple->Fill(Ehit,yhit);
> }
>
> // plots
> TCanvas* c1 = new TCanvas("c1","c1",1);
> c1->Divide(2,2);
>
> // trick with 1D histograms
> c1->cd(1);
> ntuple->Draw("Ehit");
> TH1F * myh1 =(TH1F *) htemp->Clone();
> myh1->SetName("myh1");
> c1->cd(2);
> myh1->Draw(); // this works
>
> // trick with 2D histograms - doesn't work!
> c1->cd(3);
> ntuple->Draw("Ehit:yhit");
> TH2F *myh2 = (TH2F *) htemp->Clone();
> myh2->SetName("myh2");
> c1->cd(4);
> myh2->Draw(); // it is empty!
> }
>
>
Dr. Otto Schaile Sektion Physik, LMU Muenchen
Phone: +49 89 289 14070 Am Coulombwall 1, D-85748 Garching, Germany
GSM: +49 171 4312031
FAX: +49 89 289 14072 EMail: Otto.Schaile@Physik.Uni-Muenchen.DE
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