gr007_multigraph.C File Reference

Detailed Description

TMultiGraph is used to combine multiple graphs into one plot.

Allowing to overlay different graphs can be useful for comparing different datasets or for plotting multiple related graphs on the same canvas.

 
 
void gr007_multigraph() {
   gStyle->SetOptFit();
   auto c1 = new TCanvas("c1","multigraph",700,500);
   c1->SetGrid();
 
   //Initialize a TMultiGraph to hold multiple graphs
   //This ensures the entire dataset from all added graphs is visible without manual range adjustments.
   auto mg = new TMultiGraph();
 
   //Create first graph
   const Int_t n1 = 10;
   Double_t px1[] = {-0.1, 0.05, 0.25, 0.35, 0.5, 0.61,0.7,0.85,0.89,0.95};
   Double_t py1[] = {-1,2.9,5.6,7.4,9,9.6,8.7,6.3,4.5,1};
   Double_t ex1[] = {.05,.1,.07,.07,.04,.05,.06,.07,.08,.05};
   Double_t ey1[] = {.8,.7,.6,.5,.4,.4,.5,.6,.7,.8};
   auto gr1 = new TGraphErrors(n1,px1,py1,ex1,ey1);
   gr1->SetMarkerColor(kBlue);
   gr1->SetMarkerStyle(21);
 
   gr1->Fit("gaus","q");
   auto func1 = (TF1 *) gr1->GetListOfFunctions()->FindObject("gaus");
   func1->SetLineColor(kBlue);
   
   //Add the first graph to the multigraph
   mg->Add(gr1);
 
   //Create second graph
   const Int_t n2 = 10;
   Float_t x2[]  = {-0.28, 0.005, 0.19, 0.29, 0.45, 0.56,0.65,0.80,0.90,1.01};
   Float_t y2[]  = {2.1,3.86,7,9,10,10.55,9.64,7.26,5.42,2};
   Float_t ex2[] = {.04,.12,.08,.06,.05,.04,.07,.06,.08,.04};
   Float_t ey2[] = {.6,.8,.7,.4,.3,.3,.4,.5,.6,.7};
   auto gr2 = new TGraphErrors(n2,x2,y2,ex2,ey2);
   gr2->SetMarkerColor(kRed);
   gr2->SetMarkerStyle(20);
 
   gr2->Fit("pol5","q");
   auto func2 = (TF1 *) gr2->GetListOfFunctions()->FindObject("pol5");
   func2->SetLineColor(kRed);
   func2->SetLineStyle(2);
 
   //Add the second graph to the multigraph
   mg->Add(gr2);
 
   mg->Draw("ap");
 
   //Force drawing of canvas to generate the fit TPaveStats
   c1->Update();
 
   auto stats1 = (TPaveStats*) gr1->GetListOfFunctions()->FindObject("stats");
   auto stats2 = (TPaveStats*) gr2->GetListOfFunctions()->FindObject("stats");
 
   if (stats1 && stats2) {
      stats1->SetTextColor(kBlue);
      stats2->SetTextColor(kRed);
      stats1->SetX1NDC(0.12); stats1->SetX2NDC(0.32); stats1->SetY1NDC(0.82);
      stats2->SetX1NDC(0.72); stats2->SetX2NDC(0.92); stats2->SetY1NDC(0.75);
      c1->Modified();
   }
}

Author

Rene Brun

Definition in file gr007_multigraph.C.