Overflow bin with Rebin

From: Jeff Hartnell <j.j.hartnell_at_rl.ac.uk>
Date: Tue, 24 Jan 2006 16:37:58 +0000

Hi,
I've noticed that the overflow bin disappears when you Rebin a histogram (see example macro pasted below). Consequently the overflow value in the stats box is zero. Is there a legitimate reason for this?

I'm using ROOT 5.08/00 on SUSE linux 10.

Thanks,
Jeff.

void rebin()
{

   gROOT->Reset();
//turn off the stats box printing

   gStyle->SetOptStat(1111111);
//gStyle->SetOptStat(0);

   gStyle->SetOptFit(11111);
   gStyle->SetPalette(1);
   gStyle->SetTitleFontSize(0.06);
   gStyle->SetTitleFillColor(0);
   gStyle->SetTitleBorderSize(0);
   gStyle->SetFrameBorderMode(0);
   gStyle->SetStatColor(0);

   gStyle->SetStatW(0.3);
   gStyle->SetStatH(0.2);

   TH1F* htest=new TH1F("htest","htest",440,-1.1,1.1);

//entries in range

   htest->Fill(0.1);
   htest->Fill(0.3);
   htest->Fill(-0.5);
   htest->Fill(-0.7);

//underflow entries

   htest->Fill(-2);
   htest->Fill(-3);

//overflow entries

   htest->Fill(5);
   htest->Fill(6);
   htest->Fill(100);

   cout<<endl<<"Before rebin:"<<endl;
   cout<<"underflow="<<htest->GetBinContent(0)<<endl;    Int_t n=htest->GetNbinsX();
   cout<<"n bins="<<n<<endl;
   cout<<"overflow="<<htest->GetBinContent(n+1)<<endl;

   TCanvas* c=new TCanvas("c","c",

                         0,0,1000,1150);

   c->SetFillColor(0);
   c->Divide(1,2);
   c->cd(1);

   htest->DrawClone();

   Int_t rebin=2;
   htest->Rebin(rebin);

   cout<<endl<<"After rebin:"<<endl;
   cout<<"underflow="<<htest->GetBinContent(0)<<endl;    Int_t n2=htest->GetNbinsX();

   cout<<"n2="<<n2<<endl;
   cout<<"overflow (with n2)="<<htest->GetBinContent(n2+1)<<endl;
   cout<<"other (with n2)="<<htest->GetBinContent(n2+2)<<endl;
   cout<<"other (with n2)="<<htest->GetBinContent(n2-1)<<endl;

//try with old number of bins:

   cout<<"overflow (with n)="<<htest->GetBinContent(n+1)<<endl;
   cout<<"other (with n)="<<htest->GetBinContent(n+2)<<endl;
   cout<<"other (with n)="<<htest->GetBinContent(n-1)<<endl;

   c->cd(2);
   htest->Draw();
} Received on Tue Jan 24 2006 - 17:37:43 MET