#include "TTree.h"
#include "TF1.h"
#include "TH2D.h"
#include "TCanvas.h"
#include "TMath.h"
#include "TNtuple.h"

#include <iostream>
#include <fstream>
#include <string>
#include "Riostream.h"
using namespace std;


void example(){
	
gROOT->Reset();

   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 xmin    = 0.1;
   Float_t xmax    = 84.1;
   const Int_t bins = 21;
   Float_t binW = (xmax-xmin)/(float)bins;

   Double_t xv[bins], yv[bins];
   
   Double_t *xntuple = ntuple->GetVal(1); //xntuple is x
   Double_t *yntuple = ntuple->GetVal(0); //yntuple is log(y/x)
   
   Double_t xaxis, yaxis;
   
   Float_t s = xmin;

   for(Int_t b=0; b<bins; b++){
      yaxis = yntuple[b];
      yv[b] = yaxis;
      xv[b] = s;
      s += binW;  //bin width is 4 
      
   }

	
   cout << xv[0] << " and " << yv[0] << '\n';
   cout << xv[1] << " and " << yv[1] << '\n';
   cout << xv[4] << " and " << yv[4] << '\n';
   
   
   
}