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();

}