{
  TNtuple* nt = new TNtuple("nt","","a:b:c");
  TCanvas *Can = new TCanvas("Can","Can",200,10,800,400);
  Can->Divide(4,2);
  
  Double_t x[16] = {1.00, 2.00, 6.00, 7.00, 3.00, 10.00, 0.20, 5.55,
                    20.50, 9.75, 1.50, 8.00, 5.00, 0.95, 3.85, 8.70};
  Double_t y[16] = {1.00, 2.00, 6.00, 7.00, 3.00, 10.00, 0.20, 5.55,
		    20.50, 9.75, 1.50, 8.00, 5.00, 0.95, 3.85, 8.70};
  Double_t z[16] = {0.001, 2.50, 600.00, 0.00001, 30.00, 10.001, 300000.0, 500000.55,
		    20.50, 9.75, 280000.50, 8.00, 5.00, 0.95, 3.85, 8.70};
  
  Double_t x3, y3, z3;
  
  for (Int_t h1 =0;h1<16;++h1) {
    x3 = x[h1];
    y3 = y[h1];
    z3 = z[h1]; nt->Fill(x3,y3,z3);
  }
  gStyle->SetOptStat(0);
  gStyle->SetPalette(1,0);
  nt->SetMarkerStyle(20);
  nt->SetMarkerSize(1);
  
  nt->SetEstimate(nt->GetEntries() + 1);
  Double_t xmin = nt->GetMinimum("a"); // "a" is X in the nt->Draw below
  Double_t xmax = nt->GetMaximum("a");
  Double_t ymin = nt->GetMinimum("b"); // "b" is Y in the nt->Draw below
  Double_t ymax = nt->GetMaximum("b");
  Double_t hxmin = xmin;
  Double_t hymin = ymin;
  
#if 0 /* 0 or 1 */
  xmin = 0.0; // enforce xmin = 0
  ymin = 0.0; // enforce ymin = 0
#endif /* 0 or 1 */
  
  Int_t xnbins = 100;
  Int_t ynbins = 100;
  
#if 0 /* 0 or 1 */
  xnbins = 40; // use the same number as for "automatically" creates histograms
  ynbins = 40; // use the same number as for "automatically" creates histograms
#endif /* 0 or 1 */
  
  TH2F *htemp;
  
  Can->cd(1);
  nt->Draw("b:a", "", ""); // note: TTree::Draw creates a "htemp"
  gPad->Modified(); gPad->Update();
  gPad->SetLogx(1);
  gPad->SetLogy(1);
  
  Can->cd(2);
  nt->Draw("b:a", "", ""); // note: TTree::Draw creates a "htemp"
  gPad->Modified(); gPad->Update();
  htemp = (TH2F *)gPad->GetPrimitive("htemp");
  if (htemp) {
    htemp->GetXaxis()->SetLimits(xmin, xmax); // set proper "htemp" X axis limits
    htemp->GetYaxis()->SetLimits(ymin, ymax); // set proper "htemp" Y axis limits
  }
  gPad->SetLogx(1);
  gPad->SetLogy(1);
  
  Can->cd(3);
  nt->Draw("b:a>>auto_hba", "", ""); // note: TTree::Draw creates "auto_hba"
  gPad->Modified(); gPad->Update();
  TH2F *auto_hba = (TH2F *)gPad->GetPrimitive("auto_hba");
  if (auto_hba) {
    auto_hba->GetXaxis()->SetLimits(xmin, xmax); // set proper "htemp" X axis limits
    auto_hba->GetYaxis()->SetLimits(ymin, ymax); // set proper "htemp" Y axis limits
  }
  gPad->SetLogx(1);
  gPad->SetLogy(1);
  
  Can->cd(4);
  TH2F *hba = new TH2F("hba", "b:a>>hba", xnbins, hxmin, xmax, ynbins, hymin, ymax);
  nt->Draw("b:a>>hba", "", "");
  gPad->Modified(); gPad->Update();
  hba->GetXaxis()->SetLimits(xmin, xmax); // set proper "htemp" X axis limits
  hba->GetYaxis()->SetLimits(ymin, ymax); // set proper "htemp" Y axis limits
  gPad->SetLogx(1);
  gPad->SetLogy(1);
  
  Can->cd(5);
  nt->Draw("b:a:c", "", "colz"); // note: TTree::Draw creates a "htemp"
  gPad->Modified(); gPad->Update();
  gPad->SetLogx(1);
  gPad->SetLogy(1);
  
  Can->cd(6);
  nt->Draw("b:a:c", "", "colz"); // note: TTree::Draw creates a "htemp"
  gPad->Modified(); gPad->Update();
  htemp = (TH2F *)gPad->GetPrimitive("htemp");
  if (htemp) {
    htemp->GetXaxis()->SetLimits(xmin, xmax); // set proper "htemp" X axis limits
    htemp->GetYaxis()->SetLimits(ymin, ymax); // set proper "htemp" Y axis limits
  }
  gPad->SetLogx(1);
  gPad->SetLogy(1);
  
  Can->cd(7);
  nt->Draw("b:a:c>>auto_hbac", "", "colz"); // note: TTree::Draw creates "auto_hbac"
  gPad->Modified(); gPad->Update();
  TH2F *auto_hbac = (TH2F *)gPad->GetPrimitive("auto_hbac");
  if (auto_hbac) {
    auto_hbac->GetXaxis()->SetLimits(xmin, xmax); // set proper "htemp" X axis limits
    auto_hbac->GetYaxis()->SetLimits(ymin, ymax); // set proper "htemp" Y axis limits
  }
  gPad->SetLogx(1);
  gPad->SetLogy(1);
  
  Can->cd(8);
  TH2F *hbac = new TH2F("hbac", "b:a:c>>hbac", xnbins, hxmin, xmax, ynbins, hymin, ymax);
  nt->Draw("b:a:c>>hbac", "", "colz");
  gPad->Modified(); gPad->Update();
  hbac->GetXaxis()->SetLimits(xmin, xmax); // set proper "htemp" X axis limits
  hbac->GetYaxis()->SetLimits(ymin, ymax); // set proper "htemp" Y axis limits
  gPad->SetLogx(1);
  gPad->SetLogy(1);
  
  Can->cd(0);
}