rf105_funcbinding.C

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/// \file
/// \ingroup tutorial_roofit
/// \notebook -js
///  'BASIC FUNCTIONALITY' RooFit tutorial macro #105
///
///   Demonstration of binding ROOT Math functions as RooFit functions
///   and pdfs
/// \macro_image
/// \macro_output
/// \macro_code
/// \author 07/2008 - Wouter Verkerke 


#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"
#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* errorFunc = bindFunction("erf",TMath::Erf,x) ;

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

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

}