ROOT logo

From $ROOTSYS/tutorials/hist/hsum.C

// histograms filled and drawn in a loop
void hsum() {
//
// To see the output of this macro, click begin_html <a href="gif/hsum.gif" >here</a> end_html
//    Simple example illustrating how to use the C++ interpreter	
//    to fill histograms in a loop and show the graphics results
//Author: Rene Brun

  TCanvas *c1 = new TCanvas("c1","The HSUM example",200,10,600,400);
  c1->SetGrid();

  gBenchmark->Start("hsum");

// Create some histograms.
  total  = new TH1F("total","This is the total distribution",100,-4,4);
  main   = new TH1F("main","Main contributor",100,-4,4);
  s1     = new TH1F("s1","This is the first signal",100,-4,4);
  s2     = new TH1F("s2","This is the second signal",100,-4,4);
  total->Sumw2();  // store the sum of squares of weights
  total->SetMarkerStyle(21);
  total->SetMarkerSize(0.7);
  main->SetFillColor(16);
  s1->SetFillColor(42);
  s2->SetFillColor(46);
  TSlider *slider = 0;

// Fill histograms randomly
  gRandom->SetSeed();
  const Int_t kUPDATE = 500;
  Float_t xs1, xs2, xmain;
  for ( Int_t i=0; i<10000; i++) {
     xmain = gRandom->Gaus(-1,1.5);
     xs1   = gRandom->Gaus(-0.5,0.5);
     xs2   = gRandom->Landau(1,0.15);
     main->Fill(xmain);
     s1->Fill(xs1,0.3);
     s2->Fill(xs2,0.2);
     total->Fill(xmain);
     total->Fill(xs1,0.3);
     total->Fill(xs2,0.2);
     if (i && (i%kUPDATE) == 0) {
        if (i == kUPDATE) {
           total->Draw("e1p");
           main->Draw("same");
           s1->Draw("same");
           s2->Draw("same");
           c1->Update();
           slider = new TSlider("slider",
              "test",4.2,0,4.6,total->GetMaximum(),38);
           slider->SetFillColor(46);
        }
        if (slider) slider->SetRange(0,Float_t(i)/10000.);
        c1->Modified();
        c1->Update();
     }
  }
  slider->SetRange(0,1);
  total->Draw("sameaxis"); // to redraw axis hidden by the fill area
  c1->Modified();
  gBenchmark->Show("hsum");
}
 hsum.C:1
 hsum.C:2
 hsum.C:3
 hsum.C:4
 hsum.C:5
 hsum.C:6
 hsum.C:7
 hsum.C:8
 hsum.C:9
 hsum.C:10
 hsum.C:11
 hsum.C:12
 hsum.C:13
 hsum.C:14
 hsum.C:15
 hsum.C:16
 hsum.C:17
 hsum.C:18
 hsum.C:19
 hsum.C:20
 hsum.C:21
 hsum.C:22
 hsum.C:23
 hsum.C:24
 hsum.C:25
 hsum.C:26
 hsum.C:27
 hsum.C:28
 hsum.C:29
 hsum.C:30
 hsum.C:31
 hsum.C:32
 hsum.C:33
 hsum.C:34
 hsum.C:35
 hsum.C:36
 hsum.C:37
 hsum.C:38
 hsum.C:39
 hsum.C:40
 hsum.C:41
 hsum.C:42
 hsum.C:43
 hsum.C:44
 hsum.C:45
 hsum.C:46
 hsum.C:47
 hsum.C:48
 hsum.C:49
 hsum.C:50
 hsum.C:51
 hsum.C:52
 hsum.C:53
 hsum.C:54
 hsum.C:55
 hsum.C:56
 hsum.C:57
 hsum.C:58
 hsum.C:59
 hsum.C:60
 hsum.C:61
 hsum.C:62
thumb