{
  TCanvas *c1 = new TCanvas("c1", "c1", 700, 500);
  c1->SetLogy();
  c1->SetGridx();
  c1->SetGridy();
  TF1 *gdist = new TF1("gdist", "TMath::GammaDist(x, [0], [1], [2])", 0, 10);
  gdist->SetParameters(0.5, 0., 1.);
  gdist->SetLineColor(2);
  TF1 *gdist1 = gdist->DrawCopy("L");
  gdist->SetParameters(1.0, 0., 1.);
  gdist->SetLineColor(3);
  TF1 *gdist2 = gdist->DrawCopy("LSAME");
  gdist->SetParameters(2.0, 0., 1.);
  gdist->SetLineColor(4);
  TF1 *gdist3 = gdist->DrawCopy("LSAME");
  gdist->SetParameters(5.0, 0., 1.);
  gdist->SetLineColor(6);
  TF1 *gdist4 = gdist->DrawCopy("LSAME");
  auto legend = new TLegend(0.15, 0.15, 0.5, 0.35);
  legend->AddEntry(gdist1, "gamma = 0.5, mu = 0, beta = 1", "L");
  legend->AddEntry(gdist2, "gamma = 1.0, mu = 0, beta = 1", "L");
  legend->AddEntry(gdist3, "gamma = 2.0, mu = 0, beta = 1", "L");
  legend->AddEntry(gdist4, "gamma = 5.0, mu = 0, beta = 1", "L");
  legend->Draw();
}