multigraph.C

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/// \file
/// \ingroup tutorial_graphs
/// \notebook
/// Create and Draw a TMultiGraph.
///
/// \macro_image
/// \macro_code
///
/// \author Rene Brun
 
void multigraph()
{
   gStyle->SetOptFit();
   auto c1 = new TCanvas("c1", "multigraph", 700, 500);
   c1->SetGrid();
 
   // draw a frame to define the range
   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);
 
   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(kDashed);
 
   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();
   }
}