On Tue, 7 Aug 2001, Rene Brun wrote: Dear Rene, Just saw your mail to Tomasso. > Hi Tommaso, > > Variables in a TNtuple are of type Float_t not Double_t. > You have two other problems in your script > - never use gROOT->Reset() in a named macro Why, what could be a problem? Thanks, Ilia > - the loop index starts at 0, not 1 > > You have 3 ways (at least) to check the content of your ntuple. > - using teh browser, double click on your variable "p" > - use nf->Show(ki) to dump the values of entry ki > - use nf->Scan(); > > Rene Brun > > Tommaso Chiarusi wrote: > > > > Hello rooters, > > > > According to the userguide, I wrote the following: > > Note: > > 1. "vario.root" is the root file in which I have stored my ntuple. > > 2. "front" is the name of my ntuple (in "vario.root" there are many > > other ntuples!). > > 3. "p" is the variable that I want to plot. ("p" is either the name of > > the TLeaf inside the ntuple "front" and of the variable the histogram I > > fill with) > > > > The problem I get is that I actually do NOT Get the Entry value, but > > something like 5.30784e-315!!!!! > > > > Thank you very much! > > > > void plot() > > { > > gROOT->Reset(); > > > > TFile *f = new TFile("vario.root"); > > TNtuple *nf = (TNtuple*)f->Get("front"); > > > > > > Int_t entries = (Int_t)nf->GetEntries(); > > cout<<"Number of Entries: "<<entries<< endl; > > > > > > Double_t p=0; > > nf->SetBranchAddress("p",&p); > > > > TH1F *htp = new TH1F("htp","p",100,0,10); > > > > for (Int_t ki=1;ki<entries;ki++) > > { > > nf->GetEntry(ki); > > htp->Fill(p); > > } > > > > TCanvas *c1 = new TCanvas("c1", "c1",515,210,540,376); > > c1->Draw(); > > htp->Draw(); > > > > // > > } > > > > Tommaso > ************************************************************************ * * * Ilia Ravinovich * * Department of Particle Physics PPE Division * * Weizmann Institute of Science Bld 892, 1D-015 * * Rehovot 76100 CERN, 1211 Geneva * * ISRAEL Switzerland * * * * PHONE : 972 8 9343187 41 22 7676437 * * FAX : 972 8 9466253 41 22 7677910 * * E-mail: Ilia.Ravinovich@weizmann.ac.il Ilia.Ravinovich@cern.ch * * * ************************************************************************
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