rf208_convolution.C

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/// \file
/// \ingroup tutorial_roofit
/// \notebook -js
///  'ADDITION AND CONVOLUTION' RooFit tutorial macro #208
///
///  One-dimensional numeric convolution
///  (require ROOT to be compiled with --enable-fftw3)
///
///  pdf = landau(t) (x) gauss(t)
///
/// \macro_image
/// \macro_output
/// \macro_code
/// \author 07/2008 - Wouter Verkerke 


#include "RooRealVar.h"
#include "RooDataSet.h"
#include "RooGaussian.h"
#include "RooLandau.h"
#include "RooFFTConvPdf.h"
#include "RooPlot.h"
#include "TCanvas.h"
#include "TAxis.h"
#include "TH1.h"
using namespace RooFit ;



void rf208_convolution()
{
   // S e t u p   c o m p o n e n t   p d f s 
   // ---------------------------------------

   // Construct observable
   RooRealVar t("t","t",-10,30) ;

   // Construct landau(t,ml,sl) ;
   RooRealVar ml("ml","mean landau",5.,-20,20) ;
   RooRealVar sl("sl","sigma landau",1,0.1,10) ;
   RooLandau landau("lx","lx",t,ml,sl) ;

   // Construct gauss(t,mg,sg)
   RooRealVar mg("mg","mg",0) ;
   RooRealVar sg("sg","sg",2,0.1,10) ;
   RooGaussian gauss("gauss","gauss",t,mg,sg) ;


   // C o n s t r u c t   c o n v o l u t i o n   p d f 
   // ---------------------------------------

   // Set #bins to be used for FFT sampling to 10000
   t.setBins(10000,"cache") ; 

   // Construct landau (x) gauss
   RooFFTConvPdf lxg("lxg","landau (X) gauss",t,landau,gauss) ;



   // S a m p l e ,   f i t   a n d   p l o t   c o n v o l u t e d   p d f 
   // ----------------------------------------------------------------------

   // Sample 1000 events in x from gxlx
   RooDataSet* data = lxg.generate(t,10000) ;

   // Fit gxlx to data
   lxg.fitTo(*data) ;

   // Plot data, landau pdf, landau (X) gauss pdf
   RooPlot* frame = t.frame(Title("landau (x) gauss convolution")) ;
   data->plotOn(frame) ;
   lxg.plotOn(frame) ;
   landau.plotOn(frame,LineStyle(kDashed)) ;


   // Draw frame on canvas
   new TCanvas("rf208_convolution","rf208_convolution",600,600) ;
   gPad->SetLeftMargin(0.15) ; frame->GetYaxis()->SetTitleOffset(1.4) ; frame->Draw() ;

}