{
   TCanvas *can = new TCanvas("can","plotz",900,700);
   TH2D *blank = new TH2D("h2","plot",100,0.,80.,100,0.,4.);

   ifstream in;
   in.open("plot.txt");

   Float_t x,y;
   Int_t nlines = 0;
   TNtuple *ntuple = new TNtuple("ntuple","ntuple example","x:y");

   while(1){
      in >>x>>y;
      if(!in.good()) break;
      ntuple->Fill(x,y);
      nlines++;
   }
   printf("nlines = %d\n",nlines);

   ntuple->Draw("log10(y/x):x>>h2","x>0");

   in.close();

   Float_t x_min    = 0.1;
   Float_t x_max    = 100.;
   const Int_t bins = 200;
   Float_t binW = (x_max-x_min)/(float)bins;

   Double_t xv[bins], yv[bins];
   Double_t *xntuple = ntuple->GetVal(0);
   Double_t *yntuple = ntuple->GetVal(1);
   Double_t xaxis, yaxis;

   for(Int_t b=0; b<bins; b++){
      xaxis = xntuple[b];
      if (x>0) {
          yaxis = log10(yntuple[b]/xntuple[b]);
      } else {
          yaxis = 0;
      }
      xv[b] = xaxis;
      yv[b] = yaxis;
   }

   cout << xv[0] << " and " << yv[0] << endl;
   cout << xv[1] << " and " << yv[1] << endl;
}