// An example application of this fit is given below. For a TH1* histogram
 //("data") fitted as the sum of three Monte Carlo sources ("mc"):

 {
   TFile d1("DataNonQcd.root");//data file

   TFile f1("MetcontrolFit.root");// QCD file

   TFile f2("T1_Mc_NonQCD.root");//ttbar signal file

   TFile f3("bkgBaseline.root");//bkg file
   
   
   TH1F *dmb  = (TH1F*)d1.Get("final_met")->Clone("data2");//data
   //TH1F *data  = (TH1F*)d1.Get("final_met");
   TH1F *mc0   = (TH1F*)f1.Get("data_minus_sigmc_and_bkg_metControl");//qcd template

   TH1F *mc1    = (TH1F*)f2.Get("final_met");//ttbar
   mc1->Scale(1/0.036);
   cout << "Integral for ttbar unscaled   " << mc1->Integral() << endl;

   TH1F *mc2    = (TH1F*)f3.Get("final_met");//bkg
   



   

   dmb->Add(mc2, -1);
   
   
   //TH1F *data;                              //data histogram
   //TH1F *mc0;                               // first MC histogram
  // TH1F *mc1;                               // second MC histogram
  // TH1F *mc2;                               // third MC histogram
                                        // retrieve histograms
   TObjArray *mc = new TObjArray(2);        // MC histograms are put in this array
   mc->Add(mc0);
   mc->Add(mc1);
   //mc->Add(mc2);
   

 
  //TFractionFitter* fit = new TFractionFitter(data, mc);
   TFractionFitter* fit = new TFractionFitter(dmb, mc); // initialise
   fit->Constrain(1,0.0,1.0);               // constrain fraction 1 to be between 0 and 1
   fit->SetRangeX(1,15);                    // use only the first 15 bins in the fit
   Int_t status = fit->Fit();               // perform the fit
   std::cout << "fit status: " << status << std::endl;
   if (status == 0) {                       // check on fit status
     TH1F* result = (TH1F*) fit->GetPlot();
     //result->SetDirectory(0);
     dmb->Draw("Ep");
     result->Draw("same");
     
;
    
   }
 }