Logo ROOT   6.21/01
Reference Guide
hsum.C File Reference

Detailed Description

View in nbviewer Open in SWAN Histograms filled and drawn in a loop.

Simple example illustrating how to use the C++ interpreter to fill histograms in a loop and show the graphics results

pict1_hsum.C.png
void hsum() {
TCanvas *c1 = new TCanvas("c1","The HSUM example",200,10,600,400);
c1->SetGrid();
gBenchmark->Start("hsum");
// Create some histograms.
auto total = new TH1F("total","This is the total distribution",100,-4,4);
auto main = new TH1F("main","Main contributor",100,-4,4);
auto s1 = new TH1F("s1","This is the first signal",100,-4,4);
auto 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
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");
}
Author
Rene Brun

Definition in file hsum.C.