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rf604_constraints.C
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1 /// \file
2 /// \ingroup tutorial_roofit
3 /// \notebook -nodraw
4 /// 'LIKELIHOOD AND MINIMIZATION' RooFit tutorial macro #604
5 ///
6 /// Fitting with constraints
7 ///
8 /// \macro_output
9 /// \macro_code
10 /// \author 07/2008 - Wouter Verkerke
11 
12 
13 #include "RooRealVar.h"
14 #include "RooDataSet.h"
15 #include "RooGaussian.h"
16 #include "RooConstVar.h"
17 #include "RooPolynomial.h"
18 #include "RooAddPdf.h"
19 #include "RooProdPdf.h"
20 #include "RooFitResult.h"
21 #include "RooPlot.h"
22 #include "TCanvas.h"
23 #include "TAxis.h"
24 #include "TH1.h"
25 using namespace RooFit ;
26 
27 
28 void rf604_constraints()
29 {
30 
31  // C r e a t e m o d e l a n d d a t a s e t
32  // ----------------------------------------------
33 
34  // Construct a Gaussian p.d.f
35  RooRealVar x("x","x",-10,10) ;
36 
37  RooRealVar m("m","m",0,-10,10) ;
38  RooRealVar s("s","s",2,0.1,10) ;
39  RooGaussian gauss("gauss","gauss(x,m,s)",x,m,s) ;
40 
41  // Construct a flat p.d.f (polynomial of 0th order)
42  RooPolynomial poly("poly","poly(x)",x) ;
43 
44  // Construct model = f*gauss + (1-f)*poly
45  RooRealVar f("f","f",0.5,0.,1.) ;
46  RooAddPdf model("model","model",RooArgSet(gauss,poly),f) ;
47 
48  // Generate small dataset for use in fitting below
49  RooDataSet* d = model.generate(x,50) ;
50 
51 
52 
53  // C r e a t e c o n s t r a i n t p d f
54  // -----------------------------------------
55 
56  // Construct Gaussian constraint p.d.f on parameter f at 0.8 with resolution of 0.1
57  RooGaussian fconstraint("fconstraint","fconstraint",f,RooConst(0.8),RooConst(0.1)) ;
58 
59 
60 
61  // M E T H O D 1 - A d d i n t e r n a l c o n s t r a i n t t o m o d e l
62  // -------------------------------------------------------------------------------------
63 
64  // Multiply constraint term with regular p.d.f using RooProdPdf
65  // Specify in fitTo() that internal constraints on parameter f should be used
66 
67  // Multiply constraint with p.d.f
68  RooProdPdf modelc("modelc","model with constraint",RooArgSet(model,fconstraint)) ;
69 
70  // Fit model (without use of constraint term)
71  RooFitResult* r1 = model.fitTo(*d,Save()) ;
72 
73  // Fit modelc with constraint term on parameter f
74  RooFitResult* r2 = modelc.fitTo(*d,Constrain(f),Save()) ;
75 
76 
77 
78  // M E T H O D 2 - S p e c i f y e x t e r n a l c o n s t r a i n t w h e n f i t t i n g
79  // -------------------------------------------------------------------------------------------------------
80 
81  // Construct another Gaussian constraint p.d.f on parameter f at 0.8 with resolution of 0.1
82  RooGaussian fconstext("fconstext","fconstext",f,RooConst(0.2),RooConst(0.1)) ;
83 
84  // Fit with external constraint
85  RooFitResult* r3 = model.fitTo(*d,ExternalConstraints(fconstext),Save()) ;
86 
87 
88 
89  // Print the fit results
90  cout << "fit result without constraint (data generated at f=0.5)" << endl ;
91  r1->Print("v") ;
92  cout << "fit result with internal constraint (data generated at f=0.5, constraint is f=0.8+/-0.2)" << endl ;
93  r2->Print("v") ;
94  cout << "fit result with (another) external constraint (data generated at f=0.5, constraint is f=0.2+/-0.1)" << endl ;
95  r3->Print("v") ;
96 
97 }
RooAddPdf is an efficient implementation of a sum of PDFs of the form.
Definition: RooAddPdf.h:29
auto * m
Definition: textangle.C:8
RooProdPdf is an efficient implementation of a product of PDFs of the form.
Definition: RooProdPdf.h:31
#define f(i)
Definition: RSha256.hxx:104
virtual void Print(Option_t *options=0) const
Print TNamed name and title.
Definition: RooFitResult.h:66
Double_t x[n]
Definition: legend1.C:17
Plain Gaussian p.d.f.
Definition: RooGaussian.h:25
RooRealVar represents a fundamental (non-derived) real valued object.
Definition: RooRealVar.h:36
RooDataSet is a container class to hold unbinned data.
Definition: RooDataSet.h:29
#define d(i)
Definition: RSha256.hxx:102
static constexpr double gauss
static constexpr double s
RooCmdArg Save(Bool_t flag=kTRUE)
RooConstVar & RooConst(Double_t val)
RooPolynomial implements a polynomial p.d.f of the form By default coefficient a_0 is chosen to be 1...
Definition: RooPolynomial.h:28
RooCmdArg ExternalConstraints(const RooArgSet &constraintPdfs)
RooCmdArg Constrain(const RooArgSet &params)