reverseaxis.C

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/// \file
/// \ingroup tutorial_hist
/// \notebook
/// Example showing an histogram with reverse axis.
///
/// \macro_image
/// \macro_code
///
/// \author Olivier Couet
 
void ReverseXAxis(TH1 *h)
{
   // Remove the current axis
   h->GetXaxis()->SetLabelOffset(999);
   h->GetXaxis()->SetTickLength(0);
 
   // Redraw the new axis
   auto newxaxis = new TGaxis(gPad->GetUxmax(),
                              gPad->GetUymin(),
                              gPad->GetUxmin(),
                              gPad->GetUymin(),
                              h->GetXaxis()->GetXmin(),
                              h->GetXaxis()->GetXmax(),
                              510,"-");
   newxaxis->SetLabelOffset(-0.03);
   newxaxis->Draw();
}
 
void ReverseYAxis(TH1 *h)
{
   // Remove the current axis
   h->GetYaxis()->SetLabelOffset(999);
   h->GetYaxis()->SetTickLength(0);
 
   // Redraw the new axis
   auto newyaxis = new TGaxis(gPad->GetUxmin(),
                              gPad->GetUymax(),
                              gPad->GetUxmin(),
                              gPad->GetUymin(),
                              h->GetYaxis()->GetXmin(),
                              h->GetYaxis()->GetXmax(),
                              510,"+R");
   newyaxis->SetLabelOffset(0.01);
   newyaxis->Draw();
}
 
void reverseaxis()
{
   TH2F *hpxpy  = new TH2F("hpxpy","py vs px",40,-4,4,40,-4,4);
   Float_t px, py;
   TRandom r;
   for (Int_t i = 0; i < 25000; i++) {
      r.Rannor(px,py);
      hpxpy->Fill(px,py);
   }
   TCanvas *c1 = new TCanvas("c1");
   hpxpy->Draw("colz");
   c1->Update();
   ReverseXAxis(hpxpy);
   ReverseYAxis(hpxpy);
}