Chi2test unweigthed histogram

[omrghad]

hi dear friends;
please when i try to evaluate my output by Chi2Test in root; i have this problems:

and this is my code below:

// Example to use chi2 test for comparing two histograms 
// One unweighted histogram is compared with a weighted histogram. 
// The normalized residuals are retrieved and plotted in a simple graph. 
// The QQ plot of the normalized residual using the 
// normal distribution is also plotted. 
//
//Authors: Nikolai Gagunashvili, Daniel Haertl, Lorenzo Moneta


#include "TH1.h"
#include "TH1D.h"
#include "TF1.h"
#include "TGraph.h"
#include "TGraphQQ.h"
#include "TCanvas.h"
#include "TStyle.h"
#include "TMath.h"


TCanvas * chi2testtt()
{
  // Note: The parameter w is used to produce the 2 pictures in
  // the TH1::Chi2Test method. The 1st picture is produced with 
  // w=0 and the 2nd with w=17 (see TH1::Chi2Test() help).

  // Define Histograms.
  const Int_t n = 200;
TFile* file1= new TFile("tung20.root","READ");
TFile* file= new TFile("specto10.root","READ");
TH1D*h1=(TH1D*) file1->Get("energySpectrumFluenceTrack");
TH1D*h2=(TH1D*) file->Get("energySpectrumFluenceTrack");
double a[h1->GetNbinsX()], y[h1->GetNbinsX()];
for(int i=0;i<200;i++){
a[i]=h1->GetBinCenter(i+1);
y[i]=h1->GetBinContent(i+1);
h1->SetBinContent(i+1,(h1->GetBinContent(i+1)/150000));
}

double e[h2->GetNbinsX()], b[h2->GetNbinsX()];
for(int i=0;i<200;i++){
e[i]=h2->GetBinCenter(i+1);
b[i]=h2->GetBinContent(i+1);
h2->SetBinContent(i+1,(h2->GetBinContent(i+1)/535000));
}

  h1->SetEntries(302836);
  h2->SetEntries(302836);

//apply the chi2 test and retrieve the residuals
  Double_t res[n], x[200];
  h1->Chi2Test(h2,"UW P",res);

//Graph for Residuals
  for (Int_t i=0; i<n; i++) x[i]= 0.01 +i*0.053/200.+0.053/400.;
  TGraph *resgr = new TGraph(n,x,res);
  resgr->GetXaxis()->SetRangeUser(0.01,0.1);
  resgr->GetYaxis()->SetRangeUser(-3.5,3.5);
  resgr->GetYaxis()->SetTitle("Normalized Residuals");
  resgr->SetMarkerStyle(21);
  resgr->SetMarkerColor(2);
  resgr->SetMarkerSize(.6);
  resgr->SetTitle("Normalized Residuals");

//Quantile-Quantile plot
  TF1 *f = new TF1("f","TMath::Gaus(x,0.01,0.1)",-10,10);
  TGraphQQ *qqplot = new TGraphQQ(n,res,f);
  qqplot->SetMarkerStyle(23);
  qqplot->SetMarkerColor(5);
  qqplot->SetMarkerSize(.8);
  qqplot->SetTitle("Q-Q plot of Normalized Residuals");

//create Canvas
  TCanvas *c1 = new TCanvas("c1","Chistat Plot",10,10,700,600);
  c1->SetFillColor(33);
  c1->Divide(2,2);

// Draw Histogramms and Graphs
  c1->cd(1);
  gPad->SetFrameFillColor(21);
  h1->SetMarkerColor(4);
  h1->SetMarkerStyle(20);

  h1->Draw("E");

  c1->cd(2);
  gPad->SetFrameFillColor(21);
  h2->Draw("");
  h2->SetMarkerColor(4);
  h2->SetMarkerStyle(20);

  c1->cd(3);
  gPad->SetFrameFillColor(21);
  gPad->SetGridy();
  resgr->Draw("APL");

  c1->cd(4);
  gPad->SetFrameFillColor(21);
  qqplot->Draw("APK");

  c1->cd(0);
  
  c1->Update();
   return c1;
}

any help please about the warning problems
thank you

[eguiraud]

Hi @omrghad ,
the fit should work despite the warning and the info messages. @moneta might know how to get rid of “First histogram is not unweighted and option UW has been requested”.

Cheers,
Enrico

[moneta]

Hi,

You are applying the Chi2 test to two weighted histograms. I see that you rescale also the first histogram h, by doing: h1->SetBinContent(i+1,(h1->GetBinContent(i+1)/150000));.
In this case you need to use the option WW in `TH1::

h1->Chi2Test(h2,"WW P",res);

Lorenzo

[omrghad]

thank you so much dear Eguiraud and Moneta