#include "RooRealVar.h"
#include "RooDataSet.h"
#include "RooDataHist.h"
#include "RooGaussian.h"
#include "RooCategory.h"
#include "TCanvas.h"
#include "TAxis.h"
#include "RooPlot.h"
#include "TFile.h"
using namespace RooFit;

TRandom3 rrand(0);

void test(){

  //Define the interval for the data observable x, and the number of bins
  const double xmin=0;
  const double xmax=100;
  const int    xbins=400;

  //Create a histogram for this observable
  TH1D *hx=new TH1D("hx","hx",xbins,xmin,xmax);

  //Define the interval for the MC prediction y, and the number of bins
  const double ymin=-100;
  const double ymax=200;
  const int    ybins=1200;

  //Create a histogram for this prediction
  TH1D *hy=new TH1D("hy","hy",ybins,ymin,ymax);


  //Fill the histogram data with pseudo-events
  const double xmean=20;
  const double xsigma=1.;
  for (int ii=0;ii<100000;ii++){
    hx->Fill(rrand.Gaus(xmean,xsigma));
  }

  

  //define the true scaling value alpha (y=x*alpha)
  const double alpha=1.1;
  //Fill the MC pdf with ymean=xmean*alpha and sigma=xsigma*alpha
  const double ymean=xmean*alpha;
  const double ysigma=xsigma*alpha;
  for (int ii=0;ii<2000000;ii++){
    hy->Fill(rrand.Gaus(ymean,ysigma));
  }
 

  //Create RooRealVar x and the dataset
  RooRealVar x("x","x",xmin,xmax);
  RooDataHist dx("dx","dx",RooArgList(x),hx);

  //Create RooRealVar y and the dataset
  RooRealVar y("y","y",ymin,ymax);
  RooDataHist dy("dy","dy",RooArgList(y),hy);

  //Create RooRealVar alpha
  RooRealVar valpha("valpha","valpha",1.,0.8,1.2);
  //Create RooFormula var
  RooFormulaVar vx("vx","x*valpha",RooArgList(x,valpha));
  //Create the PDF for x
  RooHistPdf pdf("pdf","pdf",vx,y,dy,2);

  //Create a sum with a constant (usually helps to avoid PDF being exactly zero)
  auto r=RooPolynomial("pol0","pol0",x,RooArgList());
  auto f=RooRealVar("f","f",0.9,0.8,1.0);
  auto s=RooAddPdf("model","model",RooArgList(pdf,r),RooArgList(f));
  
  //Fit
  s.fitTo(dx);

  
  auto frame=x.frame();
  dx.plotOn(frame);
  pdf.plotOn(frame);
  
  frame->Draw();



}