#include<iostream>          // For printing messages to the terminal
#include<string>            // For strings
#include<TH1D.h>            // ROOT histograms
#include<TFile.h>           // ROOT files
#include<TCanvas.h>         // ROOT canvas for plotting
#include<TPad.h>            // ROOT pads for advanced plotting
#include<TLegend.h>         // ROOT legends for plots
#include<TLatex.h>          // ROOT latex for flexible text drawing
#include<TLine.h>           // ROOT support for drawing lines
#include<TPad.h>           // ROOT support for drawing lines

#include<TF1.h>    

//Breit-Wigner function
Double_t mybw(Double_t* x, Double_t* par)
{
  Double_t arg1 = 14.0/22.0; // 2 over pi
  Double_t arg2 = par[1]*par[1]*par[2]*par[2]; //Gamma=par[1]  M=par[2]
  Double_t arg3 = ((x[0]*x[0]) - (par[2]*par[2]))*((x[0]*x[0]) - (par[2]*par[2]));
  Double_t arg4 = x[0]*x[0]*x[0]*x[0]*((par[1]*par[1])/(par[2]*par[2]));
  return par[0]*arg1*arg2/(arg3 + arg4);
}


void FitData(Bool_t isMC = kTRUE){
  // Retrieve the histograms from the file
  // Open the file in read-only mode
  TFile* histFile;
  if(isMC)
    histFile = new TFile("histoMC.root");
  else
    histFile = new TFile("histodata.root");

  TH1D*  dataHisto= (TH1D*)histFile->Get("DATA");

  // Make sure you got the histograms

  if (!dataHisto)
    {
      return;
    }
  
  // Basic style
  //  Turn off the statistics box
  // Make a canvas
  TCanvas *c1 = new TCanvas("c1","c1",1500,500);
  // Move into the canvas (so anything drawn is part of this canvas)
  c1->Divide(3,1);
  c1->cd(1);gPad->SetLogy();
  dataHisto->DrawCopy();

  c1->cd(2);gPad->SetLogy();
  dataHisto->DrawCopy();
  dataHisto->Fit("gaus");
  dataHisto->DrawCopy();

  TF1 *fBW = new TF1("fBW",mybw,50.e3,200.e3,3);
  fBW->SetParameter(0,100e3);
  fBW->SetParameter(1,1e3);
  fBW->SetParameter(2,90e3);

  c1->cd(3);
  gPad->SetLogy();
  dataHisto->DrawCopy();
  dataHisto->Fit(fBW);
  dataHisto->DrawCopy();

  c1->SaveAs("fit.png");
}