th2polyBoxes.C

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/// \file
/// \ingroup tutorial_hist
/// \notebook
/// This tutorial illustrates how to create an histogram with polygonal
/// bins (TH2Poly). The bins are boxes.
///
/// \macro_image
/// \macro_code
///
/// \author Olivier Couet

TCanvas *th2polyBoxes() {
   TCanvas *ch2p2 = new TCanvas("ch2p2","ch2p2",600,400);
   gStyle->SetPalette(57);
   TH2Poly *h2p = new TH2Poly();
   h2p->SetName("Boxes");
   h2p->SetTitle("Boxes");

   Int_t i,j;
   Int_t nx = 40;
   Int_t ny = 40;
   Double_t xval1,yval1,xval2,yval2;
   Double_t dx=0.2, dy=0.1;
   xval1 = 0.;
   xval2 = dx;

   for (i = 0; i<nx; i++) {
      yval1 = 0.;
      yval2 = dy;
      for (j = 0; j<ny; j++) {
         h2p->AddBin(xval1, yval1, xval2, yval2);
         yval1 = yval2;
         yval2 = yval2+yval2*dy;
      }
      xval1 = xval2;
      xval2 = xval2+xval2*dx;
   }

   TRandom ran;
   for (i = 0; i<300000; i++) {
      h2p->Fill(50*ran.Gaus(2.,1), ran.Gaus(2.,1));
   }

   h2p->Draw("COLZ");
   return ch2p2;
}