rf108_plotbinning.C

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/// \file
/// \ingroup tutorial_roofit
/// \notebook -js
/// Basic functionality: 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();
}