#include <iostream>
#include <fstream>
#include <TMath.h>
using namespace std;
using namespace TMath;
using namespace RooFit;

void Fit(){
  TFile *f = new TFile("Example.root");
  TTree *t = (TTree*)f->Get("data");
  RooRealVar En("x","x",0,100);
  RooDataSet data("data","data",RooArgSet(En),Import(*t));

  //signal gaussian at 50keV with sigma of 5
  RooRealVar mean("mean","mean",50);
  RooRealVar sig("sig","sig",5);
  RooGaussian gss("gss","gss",En,mean,sig);

  //uniform background
  RooPolynomial p0("px","px",En);

  //sigy and bkgy are yields for each component, only variables allowed to vary
  RooRealVar sigy("sigy","sigy",1,-1000000,10);
  RooRealVar bkgy("bkgy","bkgy",1,0,9000);



  
  RooAddPdf model("model","model",
		      RooArgList(gss,p0),
		      RooArgList(sigy,bkgy));


  
  //create likelihood, minimize
  RooAbsReal *nll = model.createNLL(data,Extended(true));
  RooMinimizer min(*nll);

  //run migrad, hesse
  int result_migrad = min.migrad();
  int result_hesse = min.hesse();

  //Plot result
  TCanvas *c1 = new TCanvas("c1","c1",700,500);
  RooPlot *P = En.frame();
  data.plotOn(P,MarkerColor(kBlue));
  model.plotOn(P,LineColor(kRed));
  P->SetTitle("Spectra 228");
  P->SetName("p228"); 
  P->Draw(); 
  c1->Print("Example.pdf","pdf");
  
  //check migrad and hesse
  if(result_migrad == 0 && result_hesse == 0){
    cout << "fit succeeded" << endl;
  }
  else{
    cout << "problem" << endl;
  }

}