{
   TNtuple* nt = new TNtuple("nt","","a:b:c");
   TCanvas *Can = new TCanvas("Can","Can",200,10,600,800);
   Can->Divide(2,2);
  
   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");
  
   TH1F *htemp;
  
   Can->cd(1);
   nt->Draw("b:a", "", ""); // note: TTree::Draw creates a "htemp"
   gPad->SetLogx(1);
   gPad->SetLogy(1);
  
   Can->cd(3);
   nt->Draw("b:a", "", ""); // note: TTree::Draw creates a "htemp"
   htemp = (TH1F *)gPad->GetPrimitive("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(2);
   nt->Draw("b:a:c", "", "colz"); // note: TTree::Draw creates a "htemp"
   gPad->SetLogx(1);
   gPad->SetLogy(1);
  
   Can->cd(4);
   nt->Draw("b:a:c", "", "colz"); // note: TTree::Draw creates a "htemp"
   htemp = (TH1F *)gPad->GetPrimitive("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);
}