tutorials/analysis/ana_example.C

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void ana_example(TString fname="pid_tpccombi.root",int nevts=0)
{
        TStopwatch timer;
        timer.Start();
        
        gROOT->Macro("$VMCWORKDIR/gconfig/rootlogon.C");
        
    TCanvas *c1=new TCanvas("c1","c1",600,600);
        
        // the PndEventReader takes care about file/event handling
        PndEventReader evr(fname);
        
        // to attach more files: evr.Add(fname2);evr.Add(fname3); ...
        
        TH1F *mom=new TH1F("mom","P(particle)",400,0.0,5.0);
        
        // the candidates lists we need
        TCandList all;
        
        
        if (nevts==0) nevts=evr.GetEntries();
        int i=0,j;
        
        // *************
        // this is the loop through the events ... as simple as this...
        // ****************
        while (evr.GetEvent() && i++<nevts)
        {
                evr.FillList(all,"Charged");
                for (j=0;j<all.GetLength();++j)
                {
                        mom->Fill(all[j].P());
                }               
        }
        
        // ... and plot it
        
        c1->cd(); mom->Draw();
        
        // now take the time...
    timer.Stop();
    Double_t rtime = timer.RealTime();
    Double_t ctime = timer.CpuTime();
    
    printf("RealTime=%f seconds, CpuTime=%f seconds\n",rtime,ctime);
}