// Simple ROOT macro to plot a histogram.
// Modify arguments as needed.
// To execute, type .X plotDist.C
{
  TFile* f = new TFile("simpleMC.root");
  f->ls();
  TH1D* h1 = (TH1D*)f.Get("h_Exp");

  // normalize histogram to unit area
  double Ntot = h1->GetEntries();
  double dx = h1->GetXaxis()->GetBinWidth(1);
  double norm = 1./(dx*Ntot);
  h1->Scale(norm);

  h1->SetXTitle("x");
  h1->SetYTitle("f(x;#xi)");
  h1->Draw();

  // plot some things on top of it
  const int numPoints = 5;
  double x[numPoints] = {0., 1., 2., 3., 4.};
  double y[numPoints] = {0.9, 0.5, 0.3, 0.1, 0.05};
  TGraph tg(numPoints, x, y);
  tg.SetLineWidth(2);
  tg.Draw("C,same");         // C for curve, same to superimpose
}