ratioplot1.C File Reference

Detailed Description

Example creating a simple ratio plot of two histograms using the pois division option.

Two histograms are set up and filled with random numbers. The constructor of TRatioPlot takes the two histograms, name and title for the object, drawing options for the histograms (hist and E in this case) and a drawing option for the output graph. The histograms drawing options can be changed with SetH1DrawOpt and SetH2DrawOpt.

 
void ratioplot1() {
   gStyle->SetOptStat(0);
   auto C  = new TCanvas("C", "A ratio example");
   auto h1 = new TH1D("h1", "TRatioPlot Example; x; y", 50, 0, 10);
   auto h2 = new TH1D("h2", "h2", 50, 0, 10);
   auto f1 = new TF1("f1", "exp(- x/[0] )");
   f1->SetParameter(0, 3);
   h1->FillRandom("f1", 1900);
   h2->FillRandom("f1", 2000);
   h1->Sumw2();
   h2->Scale(1.9 / 2.);
   h2->SetLineColor(kRed);
 
   // Create and draw the ratio plot
   auto rp = new TRatioPlot(h1, h2);
   C->SetTicks(0, 1);
   rp->Draw();
   rp->GetLowYaxis()->SetNdivisions(505);
 
   // Add a legend to the ratio plot
   rp->GetUpperPad()->cd();
   TLegend *legend = new TLegend(0.3,0.7,0.7,0.85);
   legend->AddEntry("h1","First histogram","l");
   legend->AddEntry("h2","Second histogram","le");
   legend->Draw();
}

Author

Paul Gessinger

Definition in file ratioplot1.C.