hist017_TH1_smooth.C

/// \file
/// \ingroup tutorial_hist
/// \notebook
/// \preview Histogram smoothing.
///
/// \macro_image
/// \macro_code
///
/// \date July 2016
/// \author Rene Brun

int ipad = 1;
TCanvas *c1 = 0;

void smooth_hist(const char *fname, double xmin, double xmax, int n1, int n2)
{

   std::cout << "smoothing a " << fname << " histogram" << std::endl;

   TH1D *h1 = new TH1D("h1", "h1", 100, xmin, xmax);
   TH1D *h2 = new TH1D("h2", "h2", 100, xmin, xmax);
   h1->FillRandom(fname, n1);

   TH1D *h1_s = new TH1D(*h1);
   h1_s->SetName("h1_s");
   h1_s->Smooth();

   h2->FillRandom(fname, n2);

   double p1 = h1->Chi2Test(h2, "");
   double p2 = h1_s->Chi2Test(h2, "UU");
   if (p2 < p1)
      Error("testSmooth", "TH1::Smooth is not working correctly - a worst chi2 is obtained");

   std::cout << " chi2 test non-smoothed histo " << p1 << std::endl;
   std::cout << " chi2 test smoothed histo     " << p2 << std::endl;

   double a1 = h1->AndersonDarlingTest(h2);
   double a2 = h1_s->AndersonDarlingTest(h2);

   std::cout << " AD test non-smoothed histo " << a1 << std::endl;
   std::cout << " AD test smoothed histo     " << a2 << std::endl;

   double k1 = h1->KolmogorovTest(h2);
   double k2 = h1_s->KolmogorovTest(h2);

   std::cout << " KS test non-smoothed histo " << k1 << std::endl;
   std::cout << " KS test smoothed histo     " << k2 << std::endl;

   c1->cd(ipad++);
   h1->Draw("E");
   h1_s->SetLineColor(kRed);
   h1_s->Draw("same");
   h2->Scale(double(n1) / n2);
   h2->SetLineColor(kGreen);
   h2->Draw("same");
}

void hist017_TH1_smooth(int n1 = 1000, int n2 = 1000000)
{

   TH1::AddDirectory(false);

   c1 = new TCanvas();
   c1->Divide(1, 3);

   smooth_hist("gaus", -5, 5, n1, n2);
   smooth_hist("landau", -5, 15, n1, n2);
   smooth_hist("expo", -5, 0, n1, n2);
}