rf108_plotbinning.C

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/// \file
/// \ingroup tutorial_roofit
/// \notebook -js
///  'BASIC FUNCTIONALITY' RooFit tutorial macro #108
///
///  Plotting unbinned data with alternate and variable binnings
/// \macro_image
/// \macro_output
/// \macro_code
///
/// \author 07/2008 - Wouter Verkerke


#include "RooRealVar.h"
#include "RooDataSet.h"
#include "RooGaussModel.h"
#include "RooDecay.h"
#include "RooBMixDecay.h"
#include "RooCategory.h"
#include "RooBinning.h"
#include "RooPlot.h"
#include "TCanvas.h"
#include "TAxis.h"
#include "TH1.h"
using namespace RooFit ;


void rf108_plotbinning()
{

   // S e t u p   m o d e l
   // ---------------------

   // Build a B decay p.d.f with mixing
   RooRealVar dt("dt","dt",-20,20) ;
   RooRealVar dm("dm","dm",0.472) ;
   RooRealVar tau("tau","tau",1.547) ;
   RooRealVar w("w","mistag rate",0.1) ;
   RooRealVar dw("dw","delta mistag rate",0.) ;

   RooCategory mixState("mixState","B0/B0bar mixing state") ;
   mixState.defineType("mixed",-1) ;
   mixState.defineType("unmixed",1) ;
   RooCategory tagFlav("tagFlav","Flavour of the tagged B0") ;
   tagFlav.defineType("B0",1) ;
   tagFlav.defineType("B0bar",-1) ;

   // Build a gaussian resolution model
   RooRealVar bias1("bias1","bias1",0) ;
   RooRealVar sigma1("sigma1","sigma1",0.1) ;
   RooGaussModel gm1("gm1","gauss model 1",dt,bias1,sigma1) ;

   // Construct Bdecay (x) gauss
   RooBMixDecay bmix("bmix","decay",dt,mixState,tagFlav,tau,dm,w,dw,gm1,RooBMixDecay::DoubleSided) ;


   // S a m p l e   d a t a   f r o m   m o d e l
   // --------------------------------------------

   // Sample 2000 events in (dt,mixState,tagFlav) from bmix
   RooDataSet *data = bmix.generate(RooArgSet(dt,mixState,tagFlav),2000) ;



   // S h o w   d t   d i s t r i b u t i o n   w i t h   c u s t o m   b i n n i n g
   // -------------------------------------------------------------------------------

   // Make plot of dt distribution of data in range (-15,15) with fine binning for dt>0 and coarse binning for dt<0

   // Create binning object with range (-15,15)
   RooBinning tbins(-15,15) ;

   // Add 60 bins with uniform spacing in range (-15,0)
   tbins.addUniform(60,-15,0) ;

   // Add 15 bins with uniform spacing in range (0,15)
   tbins.addUniform(15,0,15) ;

   // Make plot with specified binning
   RooPlot* dtframe = dt.frame(Range(-15,15),Title("dt distribution with custom binning")) ;
   data->plotOn(dtframe,Binning(tbins)) ;
   bmix.plotOn(dtframe) ;

   // NB: Note that bin density for each bin is adjusted to that of default frame binning as shown
   // in Y axis label (100 bins --> Events/0.4*Xaxis-dim) so that all bins represent a consistent density distribution


   // S h o w   m i x s t a t e   a s y m m e t r y  w i t h   c u s t o m   b i n n i n g
   // ------------------------------------------------------------------------------------

   // Make plot of dt distribution of data asymmetry in 'mixState' with variable binning

   // Create binning object with range (-10,10)
   RooBinning abins(-10,10) ;

   // Add boundaries at 0, (-1,1), (-2,2), (-3,3), (-4,4) and (-6,6)
   abins.addBoundary(0) ;
   abins.addBoundaryPair(1) ;
   abins.addBoundaryPair(2) ;
   abins.addBoundaryPair(3) ;
   abins.addBoundaryPair(4) ;
   abins.addBoundaryPair(6) ;

   // Create plot frame in dt
   RooPlot* aframe = dt.frame(Range(-10,10),Title("mixState asymmetry distribution with custom binning")) ;

   // Plot mixState asymmetry of data with specified custom binning
   data->plotOn(aframe,Asymmetry(mixState),Binning(abins)) ;

   // Plot corresponding property of p.d.f
   bmix.plotOn(aframe,Asymmetry(mixState)) ;

   // Adjust vertical range of plot to sensible values for an asymmetry
   aframe->SetMinimum(-1.1) ;
   aframe->SetMaximum(1.1) ;

   // NB: For asymmetry distributions no density corrects are needed (and are thus not applied)


   // Draw plots on canvas
   TCanvas* c = new TCanvas("rf108_plotbinning","rf108_plotbinning",800,400) ;
   c->Divide(2) ;
   c->cd(1) ; gPad->SetLeftMargin(0.15) ; dtframe->GetYaxis()->SetTitleOffset(1.6) ; dtframe->Draw() ;
   c->cd(2) ; gPad->SetLeftMargin(0.15) ; aframe->GetYaxis()->SetTitleOffset(1.6) ; aframe->Draw() ;

}