ForestErrAnal Lab 8.C

void DataRead() {
  TH1F *LengthHist=new TH1F("LengthHist","LengthHist",30,18.45,21.45);
  ifstream in;
  in.open("length.dat");
  Float_t Length,LengthErr;
  Int_t Counts;
  Int_t nlines=0;
  while(in.good()){
    in >> Length >> Counts;
     if(Counts>0)
       LengthErr=0.5/sqrt(Counts);
     printf( " %d \t %f +/- %f \t %d\n", nlines, Length, LengthErr, Counts);
    /*                                                                            
    */
    nlines++;

    LengthHist->Fill(Length,Counts);

  }
  LengthHist->Draw();
}