hist022_TH2_palette.C

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/// \file
/// \ingroup tutorial_hist
/// \notebook
/// \preview When an histogram is drawn with the option COLZ, a palette is automatically drawn
/// vertically on the right side of the plot. It is possible to move and resize this
/// vertical palette as shown on the left plot. The right plot demonstrates that, when the
/// width of the palette is larger than its height, the palette is automatically drawn
/// horizontally.
///
/// \macro_image
/// \macro_code
///
/// \date October 2024
/// \author Olivier Couet
 
void hist022_TH2_palette()
{
   auto c = new TCanvas("", "", 0, 0, 1100, 550);
   c->Divide(2, 1);
   gStyle->SetOptStat(0);
 
   auto h1 = new TH2D("h1", "h1", 40, -4, 4, 40, -20, 20);
   auto h2 = new TH2D("h2", "h2", 40, -4, 4, 40, -20, 20);
   float px, py;
   for (int i = 0; i < 25000; i++) {
      gRandom->Rannor(px, py);
      h1->Fill(px, 5 * py);
      gRandom->Rannor(px, py);
      h2->Fill(px, 5 * py);
   }
 
   TPad *p1 = (TPad *)c->cd(1);
   TPad *p2 = (TPad *)c->cd(2);
 
   p1->SetRightMargin(0.15);
   auto palette1 = new TPaletteAxis(4.05, -15, 4.5, 15, h1);
   h1->GetListOfFunctions()->Add(palette1);
 
   p2->SetBottomMargin(0.2);
   auto palette2 = new TPaletteAxis(-3., -25, 3., -23, h2);
   h2->GetListOfFunctions()->Add(palette2);
 
   p1->cd();
   h1->Draw("colz");
   p2->cd();
   h2->Draw("colz");
}