Re: [ROOT] What does negative zero mean?

From: Gabriel Tabacaru (tabacaru@comp.tamu.edu)
Date: Thu Apr 01 2004 - 23:36:53 MEST


Hi,

It is normal when you use "B" option for Divide() and the two histograms 
are identical! 
Look what does it mean binomial distribution. 
Below few corrections for your test.

Cheers, 
Gabriel

> void test()
> {
> 
>    TH1F* dH = new TH1F("dH","dH",10,0,10);
>    TH1F* nH = new TH1F("nH","nH",10,0,10);
>    TH1F* rH = new TH1F("rH","rH",10,0,10);
> 
>    for(Int_t i=2; i<8; i++){
>    
        Stat_t content = i;
	dH->SetBinContent(i,content);
        Stat_t content = i*1.1; //for example
        nH->SetBinContent(i,content);
>    }
> 
>    rH->Sumw2();
>    rH->Divide(nH,dH,1,1,"B");
>    rH->SetMarkerStyle(20);
>    rH->SetMarkerColor(2);
     //here option "PE" 
     rH->Draw("PE");
> 
>    for(Int_t i=1; i<=10; i++){
>      cout << i << "\t : " << rH->GetBinContent(i)
> 	 << ", " << rH->GetBinError(i) << endl;
>    }
> 
> }
> 
> I expected exact 1 efficiency plot, but I got the following:
> 
> <output> :
> 
> No points are ploted at all.
> 
> root [0] .x test.C
> <TCanvas::MakeDefCanvas>: created default TCanvas with name c1
> 1        : 0, 0
> 2        : 1, -0
> 3        : 1, -0
> 4        : 1, -0
> 5        : 1, -0
> 6        : 1, -0
> 7        : 1, -0
> 8        : 0, 0
> 9        : 0, 0
> 10       : 0, 0
> root [1]
> 
> 
> 

-- 
===============================================
Dr. Gabriel Tabacaru                          =
Cyclotron Institute - Texas A&M University    =
Univ. Drive                                   =
MS 3366, College Station, Texas 77843-3366    = 
USA                                           =
Tel.  : ++ 979 845 1411                       =
e-mail: tabacaru@comp.tamu.edu                =
        tabacaru@tamu.edu                     =
===============================================



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