#include<iostream>
#include "TRandom2.h"
#include "RooGaussian.h"
using namespace std;
using namespace RooFit;

void rooDataHist_experiments () {
  
  //RooMsgService::instance().setSilentMode(true);

  //load gaussian data
  TFile *inputfile  = new TFile("rooDataHist_experiments_input.root", "READ" );
  TH1F* myHisto = (TH1F*)inputfile->Get("myHisto");
  
  //create RooRealVar to choose min and max of RooDataHist; this affects the number of bins. If you set var between 3.0 and 3.12 (two bins), chi2/ndof will be infinite.
  RooRealVar var("var", "var", 1.0, 5.0);
  RooDataHist dh("dh", "dh", RooArgList(var), myHisto);
  cout << "RooDataHist has " << dh.numEntries() << " bins" << endl;
  
  //create gaussian PDF
  RooRealVar mean("mean", "mean", 3,0,6);
  RooRealVar sigma("sigma", "sigma", 0.5,0,1);
  //mean.setConstant(kTRUE);
  //sigma.setConstant(kTRUE);
  RooGaussian g("g","g",var, mean, sigma);
  
  //fit the PDF to the datahist
  RooFitResult * r = g.fitTo(dh, Save());
  //RooFitResult * r = g.fitTo(dh, Range(1,5), Save()); //alternative fit using Range
  
  //print number of floating parameters in the PDF
  cout << "number of floating parameters: " << r->floatParsFinal().getSize() << endl;

  RooPlot *plot = var.frame(Title("plot"));
  dh.plotOn(plot);
  g.plotOn(plot);
  double chi2_over_ndof = plot->chiSquare(r->floatParsFinal().getSize()); //tell the chiSquare method how many free parameters you have
  cout << "Chi-square over ndof: " << chi2_over_ndof << endl;
  TCanvas *can = new TCanvas("can", "can", 900,600);
  plot->Draw();
  
}