ROOT   Reference Guide
rf701_efficiencyfit.C
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1/// \file
2/// \ingroup tutorial_roofit
3/// \notebook -js
4///
5/// Special p.d.f.'s: unbinned maximum likelihood fit of an efficiency eff(x) function
6///
7/// to a dataset D(x,cut), where cut is a category encoding a selection, of which the
8/// efficiency as function of x should be described by eff(x)
9///
10/// \macro_image
11/// \macro_output
12/// \macro_code
13///
14/// \date 07/2008
15/// \author Wouter Verkerke
16
17#include "RooRealVar.h"
18#include "RooDataSet.h"
19#include "RooGaussian.h"
20#include "RooConstVar.h"
21#include "RooFormulaVar.h"
22#include "RooProdPdf.h"
23#include "RooEfficiency.h"
24#include "RooPolynomial.h"
25#include "RooCategory.h"
26#include "TCanvas.h"
27#include "TAxis.h"
28#include "RooPlot.h"
29using namespace RooFit;
30
32{
33 // C o n s t r u c t e f f i c i e n c y f u n c t i o n e ( x )
34 // -------------------------------------------------------------------
35
36 // Declare variables x,mean,sigma with associated name, title, initial value and allowed range
37 RooRealVar x("x", "x", -10, 10);
38
39 // Efficiency function eff(x;a,b)
40 RooRealVar a("a", "a", 0.4, 0, 1);
41 RooRealVar b("b", "b", 5);
42 RooRealVar c("c", "c", -1, -10, 10);
43 RooFormulaVar effFunc("effFunc", "(1-a)+a*cos((x-c)/b)", RooArgList(a, b, c, x));
44
45 // C o n s t r u c t c o n d i t i o n a l e f f i c i e n c y p d f E ( c u t | x )
46 // ------------------------------------------------------------------------------------------
47
48 // Acceptance state cut (1 or 0)
49 RooCategory cut("cut", "cutr", { {"accept", 1}, {"reject", 0} });
50
51 // Construct efficiency p.d.f eff(cut|x)
52 RooEfficiency effPdf("effPdf", "effPdf", effFunc, cut, "accept");
53
54 // G e n e r a t e d a t a ( x , c u t ) f r o m a t o y m o d e l
55 // -----------------------------------------------------------------------------
56
57 // Construct global shape p.d.f shape(x) and product model(x,cut) = eff(cut|x)*shape(x)
58 // (These are _only_ needed to generate some toy MC here to be used later)
59 RooPolynomial shapePdf("shapePdf", "shapePdf", x, RooConst(-0.095));
60 RooProdPdf model("model", "model", shapePdf, Conditional(effPdf, cut));
61
62 // Generate some toy data from model
63 RooDataSet *data = model.generate(RooArgSet(x, cut), 10000);
64
65 // F i t c o n d i t i o n a l e f f i c i e n c y p d f t o d a t a
66 // --------------------------------------------------------------------------
67
68 // Fit conditional efficiency p.d.f to data
69 effPdf.fitTo(*data, ConditionalObservables(x));
70
71 // P l o t f i t t e d , d a t a e f f i c i e n c y
72 // --------------------------------------------------------
73
74 // Plot distribution of all events and accepted fraction of events on frame
75 RooPlot *frame1 = x.frame(Bins(20), Title("Data (all, accepted)"));
76 data->plotOn(frame1);
77 data->plotOn(frame1, Cut("cut==cut::accept"), MarkerColor(kRed), LineColor(kRed));
78
79 // Plot accept/reject efficiency on data overlay fitted efficiency curve
80 RooPlot *frame2 = x.frame(Bins(20), Title("Fitted efficiency"));
81 data->plotOn(frame2, Efficiency(cut)); // needs ROOT version >= 5.21
82 effFunc.plotOn(frame2, LineColor(kRed));
83
84 // Draw all frames on a canvas
85 TCanvas *ca = new TCanvas("rf701_efficiency", "rf701_efficiency", 800, 400);
86 ca->Divide(2);
87 ca->cd(1);
89 frame1->GetYaxis()->SetTitleOffset(1.6);
90 frame1->Draw();
91 ca->cd(2);
93 frame2->GetYaxis()->SetTitleOffset(1.4);
94 frame2->Draw();
95}
#define b(i)
Definition: RSha256.hxx:100
#define c(i)
Definition: RSha256.hxx:101
@ kRed
Definition: Rtypes.h:64
virtual RooPlot * plotOn(RooPlot *frame, const RooCmdArg &arg1=RooCmdArg::none(), const RooCmdArg &arg2=RooCmdArg::none(), const RooCmdArg &arg3=RooCmdArg::none(), const RooCmdArg &arg4=RooCmdArg::none(), const RooCmdArg &arg5=RooCmdArg::none(), const RooCmdArg &arg6=RooCmdArg::none(), const RooCmdArg &arg7=RooCmdArg::none(), const RooCmdArg &arg8=RooCmdArg::none()) const
Calls RooPlot* plotOn(RooPlot* frame, const RooLinkedList& cmdList) const ;.
Definition: RooAbsData.cxx:546
RooArgList is a container object that can hold multiple RooAbsArg objects.
Definition: RooArgList.h:21
RooArgSet is a container object that can hold multiple RooAbsArg objects.
Definition: RooArgSet.h:28
RooCategory is an object to represent discrete states.
Definition: RooCategory.h:23
RooDataSet is a container class to hold unbinned data.
Definition: RooDataSet.h:33
RooEfficiency is a PDF helper class to fit efficiencies parameterized by a supplied function F.
Definition: RooEfficiency.h:27
A RooFormulaVar is a generic implementation of a real-valued object, which takes a RooArgList of serv...
Definition: RooFormulaVar.h:29
A RooPlot is a plot frame and a container for graphics objects within that frame.
Definition: RooPlot.h:44
TAxis * GetYaxis() const
Definition: RooPlot.cxx:1277
virtual void Draw(Option_t *options=0)
Draw this plot and all of the elements it contains.
Definition: RooPlot.cxx:712
RooPolynomial implements a polynomial p.d.f of the form.
Definition: RooPolynomial.h:28
RooProdPdf is an efficient implementation of a product of PDFs of the form.
Definition: RooProdPdf.h:31
RooRealVar represents a variable that can be changed from the outside.
Definition: RooRealVar.h:35
virtual void SetTitleOffset(Float_t offset=1)
Set distance between the axis and the axis title.
Definition: TAttAxis.cxx:294
The Canvas class.
Definition: TCanvas.h:27
Definition: TCanvas.cxx:701
virtual void Divide(Int_t nx=1, Int_t ny=1, Float_t xmargin=0.01, Float_t ymargin=0.01, Int_t color=0)
RooConstVar & RooConst(Double_t val)
RooCmdArg Conditional(const RooArgSet &pdfSet, const RooArgSet &depSet, Bool_t depsAreCond=kFALSE)
RooCmdArg Bins(Int_t nbin)
RooCmdArg ConditionalObservables(const RooArgSet &set)
RooCmdArg MarkerColor(Color_t color)
RooCmdArg Cut(const char *cutSpec)
RooCmdArg LineColor(Color_t color)
RooCmdArg Efficiency(const RooCategory &cat)
Double_t x[n]
Definition: legend1.C:17
The namespace RooFit contains mostly switches that change the behaviour of functions of PDFs (or othe...
const char * Title
Definition: TXMLSetup.cxx:67
auto * a
Definition: textangle.C:12