void track(){

  double x,y,z;  
  int i=0,n;
  double r[3][2650];
  
  //Infile
  ifstream in;
  in.open("TRACK.dat");
 
  //Canvas
  TCanvas *c1 = new TCanvas("c1", "Track", 1);
  
  while(1){

    i++;

    in >> x >> y >> z  ;

    r[0][i]=x;
    r[1][i]=y;
    r[2][i]=z;

    cout << i << " " << x << " " << y <<" " << z << endl ;

    if(!in.good()) break;

  }

  n=i;

  cout << x <<" "<< y <<" " << z << endl ;

  //Graph
  TGraph2D *g = new TGraph2D(n,r[0],r[1],r[2]);

  g->SetFillColor(19);
  g->SetLineColor(2);
  g->SetLineWidth(4);
  g->SetMarkerColor(4);
  g->SetMarkerStyle(21);
  g->SetTitle("electron track");
  g->Draw("P");
  
  cout << "number of lines read: "<< i << endl;

  //Close inputfile
  in.close();
}