#include "Riostream.h"
void proton() {
//  Read data from an ascii file and create a root file with an histogram and an ntuple.
//   see a variant of this macro in basic2.C
//Author: Rene Brun
      

// read file $ROOTSYS/tutorials/tree/basic.dat
// this file has 3 columns of float data
   ifstream in;
   in.open("input.dat");

   Float_t x,y;
   Int_t nlines = 0;
   TFile *f = new TFile("output.root","RECREATE");
   TH1F *h1 = new TH1F("h1","ptot distribution",100,0,2);
   TH2F *h2 = new TH2F("h2","p vs. theta",100,0,80,100,0,2);
   TNtuple *ntuple = new TNtuple("ntuple","from reduced hddm","ptot:theta");

   while (1) {
      in >> x >> y;
      if (!in.good()) break;
      if (nlines < 5) printf("x=%8f, y=%8f\n",x,y);
      h1->Fill(x);
      h2->Fill(y,x);
      ntuple->Fill(x,y);
      nlines++;
   }
   printf(" found %d points\n",nlines);

   in.close();

   f->Write();
}