Andreas,
Replace your statement
TFile ( ...
by
TFile *f = new TFile( ...
see chapter about "Object Ownership" in the Users Guide.
In your case, the TFile object is deleted when leaving the scope of
the function, together with the histograms associated to this file.
Rene Brun
Andreas WILDAUER wrote:
>
> Hi all,
>
> I have the following problem:
>
> I am trying to write a macro which reads a root ntuble file and creates some
> histograms. When I compile an execute the scripts the histograms are always
> empty.
>
> I know this has something to do with the fact that after the program finishes
> the histo go out of scope, but I dont know how to fix it.
>
> I need (a want to) compile because I am using things like std::vector aso.
> The ntuple looks ok when I check it with TBrowser.
>
> Thanks in advance
> Andi
>
> Heres how I try to do it:
>
> // Standard Includes
> #include "TFile.h"
> ...
>
> void printHistos(void)
> {
> TFile f( ... right path to the file ... );
>
> t = (TTree*)f.Get("t3333");
>
> std::vector<TH1F*>* myHistos = new std::vector<TH1F*>;
> std::vector<TString> histoTitles;
>
> histoTitles.push_back("d0");
> histoTitles.push_back("z0");
>
> TCanvas* canv = new TCanvas("m_canv", "Track Plots", 200, 200, 700,320);
> canv->Divide(5,2);
>
> t->Draw("Trk_d0>>h1(100,-3.,3.)","","");
> myHistos->push_back((TH1F*)gDirectory->Get("h1"));
>
> t->Draw("Trk_z0>>h2(100,-3.,3.)","","");
> myHistos->push_back((TH1F*)gDirectory->Get("h2"));
>
> int count = 1;
> for (std::vector<TH1F>::iterator fz = myHistos->begin();
> fz != myHistos->end(); ++fz)
> {
> canv->cd(count);
> (*fz).Draw();
> ++count;
> }
> }
> --
>
> =======================================================================
> Andreas Wildauer
> CERN/PH ATC, mailbox E25310, CH-1211 Geneva 23, Switzerland
> office 40 3-D06
> email Andreas.Wildauer@cern.ch
> tel +41 22 76 71779
> =======================================================================
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