Re: How to get an Histogram ?

From: Jordi Nadal <jnadal_at_ifae.es>
Date: Thu, 8 Sep 2011 09:32:55 +0200

Hello all and thanks for your answers,

Doing what you say :
HangingTree->Draw(raw+">>histo");
TH1D *h = (TH1D*) gROOT->FindObject("histo"); std::cout << raw << " " << h->GetMean() << std::endl;

I get :

QCDnorm_corr_mu -0.157223
QCDnorm_corr_mu_btag 0.106851

is the same problem I found doing directly the histo->GetMean()

while in the root file: (http://personal.ifae.es/jnadal/sumRootFile.root)

root [2] HangingTree->Draw("QCDnorm_corr_mu_btag>>histo") Info in <TCanvas::MakeDefCanvas>: created default TCanvas with name c1 root [3] histo->GetMean()
(const Double_t)1.69030729412928876e-01
root [4]

So the second value is failing. Maybe is not related to this issue of the histogram… maybe is because I do not erase the histogram be in each iteration...

Thanks all again!

Cheers,

Jordi

PS: I put here the macro

{
int N = 2;
TString parnames[N] = {

  //"k_ttbar",
	//"k_Wjets",
	//"Rb",
	"QCDnorm_corr_mu",
	"QCDnorm_corr_mu_btag",
	//"LarHole",


//	"BCtag",

//	"Ltag",

//	"Wjets_HFQQ",

//	"Wjets_HFC",

//	"Wjets_Berends",

//	"ttbar_ISR",

//	"ttbar_FSR",

//	//"JER",


//	"Xsect_singleTop",

//	"Xsect_DB",

//	//"bJES",


//	"Wjets_HFQQ_3ex",

//	"Wjets_HFQQ_4ex",

//	"Wjets_HFQQ_5in",

//	"Wjets_HFC_3ex",

//	"Wjets_HFC_4ex",

//	"Wjets_HFC_5in",

//	"JES_Calo",

//	"JES_Noise",

//	"JES_Perugia",

//	"JES_Herwig",

//	"JES_EtaInterCali",

//	"JES_Pileup",

//	"JES_Closure"

 };

//TFile *file = TFile::Open("ELE/Data/sumRootFile.root"); TFile *file = TFile::Open("PSE/JO_muon_PSE_RbFree/sumRootFile.root"); TTree* HangingTree = (TTree*) file->Get("HangingTree");

std::cout << "\\begin{table}[htb] " << std::endl;
std::cout << "\\begin{center} " << std::endl;
std::cout << "\\begin{tabular}{l | r | r r } " << std::endl;
std::cout << "\\hline " << std::endl;
std::cout << "\\hline" << std::endl;
std::cout << " Nuisance parameters      &  $\\alpha$ & \\multicolumn{2}{c}{$\\Delta\\alpha$} \\\\ " << std::endl;
std::cout << "\\hline " << std::endl;
std::cout << "\\hline " << std::endl;
std::cout << "\\multicolumn{4}{l}{Object selection} \\\\" << std::endl;
std::cout << "\\hline " << std::endl;

	//int binN= 100;
	//int minB = -1;
	//int maxB = 1;
	//TH1F* histo = new TH1F("histo", "histo", binN, minB, maxB);
	//TH1F* histo1 = new TH1F("histo1", "histo1", binN, minB, maxB);
	//TH1F* histo2 = new TH1F("histo2", "histo2", binN, minB, maxB);

for(int i=0; i<N;i++){

	TString raw = parnames[i]; 
	HangingTree->Draw(raw+">>histo");
//	HangingTree->Draw(raw+"_upErr>>histo1");
//	HangingTree->Draw(raw+"_downErr>>histo2");
	TH1D *h = (TH1D*) gROOT->FindObject("histo");
	std::cout << raw << " " << h->GetMean() << std::endl;

//std::cout << raw << " & " << printf("%.3f",histo->GetMean()) << " & " << printf("%.3f",histo1->GetMean()) << "& "<< printf("%.3f",histo2->GetMean()) << "\\\\" << std::endl; //std::cout << raw << " & " << histo->GetMean() << " & " << histo1->GetMean() << " & " << histo2->GetMean() << "\\\\" << std::endl;

}

std::cout << "\\hline " << std::endl;
std::cout << "\\hline" << std::endl;
std::cout << "\\end{tabular} " << std::endl;
std::cout << "\\end{center}" << std::endl;
std::cout << "\\end{table} " << std::endl;

}

On Sep 8, 2011, at 12:10 AM, suvayu ali wrote:

> Hi Jordi,
> 
> On Wed, Sep 7, 2011 at 6:02 PM, Jordi Nadal <jnadal_at_ifae.es> wrote:
>> root [1] gROOT->FindObject("Wjets_HFC_4ex")
>> (const class TObject*)0x0
>                       ^^^^^
> As you can see here, there is no object "named" Wjets_HFC_4ex so it
> returns a null pointer (as indicated above). You have to first create the
> histogram before you can retrieve it with FindObject().
> 
>> root [2] .ls
>> TFile**         PSE/JO_muon_PSE_RbFree/sumRootFile.root
>>  TFile*         PSE/JO_muon_PSE_RbFree/sumRootFile.root
>>  KEY: TTree    HangingTree;1   no lemons at that tree
>> root [3]   TH1F *Wjets_HFC = (TH1F*) gROOT->FindObject("Wjets_HFC_4ex")
>> root [4] Wjets_HFC->GetMean
>> GetMean
>> GetMeanError
>> root [4] Wjets_HFC->GetMean()
>> Error: illegal pointer to class object Wjets_HFC 0x0 550  (tmpfile):1:
>> *** Interpreter error recovered ***
> 
> So if you try the above _after_ you have plotted the histogram as in
> your first post, the above should give you the expected results.
> 
> HTH
> 
> -- 
> Suvayu
> 
> Open source is the future. It sets us free.

Received on Thu Sep 08 2011 - 09:33:06 CEST