#define residual_cxx
#include "residual.h"
#include <TH2.h>
#include <TStyle.h>
#include <TCanvas.h>

void residual::Loop()
{
//   In a ROOT session, you can do:
//      Root > .L residual.C
//      Root > residual t
//      Root > t.GetEntry(12); // Fill t data members with entry number 12
//      Root > t.Show();       // Show values of entry 12
//      Root > t.Show(16);     // Read and show values of entry 16
//      Root > t.Loop();       // Loop on all entries
//

//     This is the loop skeleton where:
//    jentry is the global entry number in the chain
//    ientry is the entry number in the current Tree
//  Note that the argument to GetEntry must be:
//    jentry for TChain::GetEntry
//    ientry for TTree::GetEntry and TBranch::GetEntry
//
//       To read only selected branches, Insert statements like:
// METHOD1:
//    fChain->SetBranchStatus("*",0);  // disable all branches
//    fChain->SetBranchStatus("branchname",1);  // activate branchname
// METHOD2: replace line
//    fChain->GetEntry(jentry);       //read all branches
//by  b_branchname->GetEntry(ientry); //read only this branch
   if (fChain == 0) return;
   Long64_t nentries = fChain->GetEntriesFast();

// Must be at least number of events
   nentries = 10000;

// book a histogram
TH1F *residual = new TH1F("residual","residual",500,0,450000);

//loop and delta t
   Long64_t nbytes = 0, nb = 0, iprevevt = -10;
   for (Long64_t jentry=0; jentry<nentries;jentry++) {
      Long64_t ientry = LoadTree(jentry);
      if (ientry < 0) break;
      nb = fChain->GetEntry(jentry);   nbytes += nb;
      if ((residual::EvtElapsedTime-iprevevt)>0)  {
	residual->Fill((residual::EvtElapsedTime-iprevevt));
	}
   iprevevt = residual::EvtElapsedTime;
      // if (Cut(ientry) < 0) continue;
   }

//poisson fit
TF1 *f1 = new TF1("f1","[0]*TMath::Power(([1]/[2]),(x/[2]))*(TMath::Exp(-([1]/[2])))/TMath::Gamma((x/[2])+1)", 0, 450000); // func, "xmin", "xmax"
f1->SetParameters(112, 1.58339e-20, 1.33478e+06); // you MUST set non-zero initial values for parameters
residual->Fit("f1","R"); // "R" = fit between "xmin" and "xmax" of the "f1"

// Build the difference histogram
TH1F DiffHist(*(residual));
DiffHist.SetNameTitle("DiffHist", "Difference in error functions (all-fit)");
  DiffHist->GetXaxis()->SetTitle("'Data'");
for ( int i = 1; i <= DiffHist->GetNbinsX(); i++ )
{
DiffHist.SetBinContent(i,residual->GetBinContent(i) - f1->GetBinContent(i));
}

// Plot simultaneously
c = new TCanvas("Comp", "Error function comparison", 500, 600);
c->Divide(1,2);
c->cd(1);
residual->SetLineColor(kBlue);
residual->DrawCopy();
f1->SetLineColor(kRed);
f1->DrawCopy("same");
c->cd(2);
c->SetGridx(1);
DiffHist.DrawCopy();



}