rf105_funcbinding.C

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//////////////////////////////////////////////////////////////////////////
//
// 'BASIC FUNCTIONALITY' RooFit tutorial macro #105
// 
//  Demonstration of binding ROOT Math functions as RooFit functions
//  and pdfs
//
// 07/2008 - Wouter Verkerke 
// 
/////////////////////////////////////////////////////////////////////////

#ifndef __CINT__
#include "RooGlobalFunc.h"
#else
// Refer to a class implemented in libRooFit to force its loading
// via the autoloader.
class Roo2DKeysPdf;
#endif
#include "RooRealVar.h"
#include "RooDataSet.h"
#include "RooGaussian.h"
#include "TCanvas.h"
#include "TAxis.h"
#include "RooPlot.h"
#include "TMath.h"
#include "TF1.h"
#include "Math/DistFunc.h"
#ifndef __CINT__
#include "RooCFunction1Binding.h" 
#include "RooCFunction3Binding.h"
#endif
#include "RooTFnBinding.h" 

using namespace RooFit;


void rf105_funcbinding()
{

  // B i n d   T M a t h : : E r f   C   f u n c t i o n
  // ---------------------------------------------------

  // Bind one-dimensional TMath::Erf function as RooAbsReal function
  RooRealVar x("x","x",-3,3) ;
  RooAbsReal* erf = bindFunction("erf",TMath::Erf,x) ;

  // Print erf definition
  erf->Print() ;

  // Plot erf on frame 
  RooPlot* frame1 = x.frame(Title("TMath::Erf bound as RooFit function")) ;
  erf->plotOn(frame1) ;


  // B i n d   R O O T : : M a t h : : b e t a _ p d f   C   f u n c t i o n
  // -----------------------------------------------------------------------

  // Bind pdf ROOT::Math::Beta with three variables as RooAbsPdf function
  RooRealVar x2("x2","x2",0,0.999) ;
  RooRealVar a("a","a",5,0,10) ;
  RooRealVar b("b","b",2,0,10) ;
  RooAbsPdf* beta = bindPdf("beta",ROOT::Math::beta_pdf,x2,a,b) ;

  // Perf beta definition
  beta->Print() ;

  // Generate some events and fit
  RooDataSet* data = beta->generate(x2,10000) ;
  beta->fitTo(*data) ;

  // Plot data and pdf on frame
  RooPlot* frame2 = x2.frame(Title("ROOT::Math::Beta bound as RooFit pdf")) ;
  data->plotOn(frame2) ;
  beta->plotOn(frame2) ;



  // B i n d   R O O T   T F 1   a s   R o o F i t   f u n c t i o n
  // ---------------------------------------------------------------

  // Create a ROOT TF1 function
  TF1 *fa1 = new TF1("fa1","sin(x)/x",0,10);
  
  // Create an observable 
  RooRealVar x3("x3","x3",0.01,20) ;

  // Create binding of TF1 object to above observable
  RooAbsReal* rfa1 = bindFunction(fa1,x3) ;

  // Print rfa1 definition
  rfa1->Print() ;

  // Make plot frame in observable, plot TF1 binding function
  RooPlot* frame3 = x3.frame(Title("TF1 bound as RooFit function")) ;
  rfa1->plotOn(frame3) ;



  TCanvas* c = new TCanvas("rf105_funcbinding","rf105_funcbinding",1200,400) ;
  c->Divide(3) ;
  c->cd(1) ; gPad->SetLeftMargin(0.15) ; frame1->GetYaxis()->SetTitleOffset(1.6) ; frame1->Draw() ;
  c->cd(2) ; gPad->SetLeftMargin(0.15) ; frame2->GetYaxis()->SetTitleOffset(1.6) ; frame2->Draw() ;
  c->cd(3) ; gPad->SetLeftMargin(0.15) ; frame3->GetYaxis()->SetTitleOffset(1.6) ; frame3->Draw() ;

}

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