doc/master/rf604__constraints_8C.html

#include "RooRealVar.h"

#include "RooDataSet.h"

#include "RooGaussian.h"

#include "RooPolynomial.h"

#include "RooAddPdf.h"

#include "RooProdPdf.h"

#include "RooFitResult.h"

#include "RooPlot.h"

#include "TCanvas.h"

#include "TAxis.h"

#include "TH1.h"

using namespace RooFit;


void rf604_constraints()

{


   // C r e a t e   m o d e l  a n d   d a t a s e t

   // ----------------------------------------------


   // Construct a Gaussian pdf

   RooRealVar x("x", "x", -10, 10);


   RooRealVar m("m", "m", 0, -10, 10);

   RooRealVar s("s", "s", 2, 0.1, 10);

   RooGaussian gauss("gauss", "gauss(x,m,s)", x, m, s);


   // Construct a flat pdf (polynomial of 0th order)

   RooPolynomial poly("poly", "poly(x)", x);


   // Construct model = f*gauss + (1-f)*poly

   RooRealVar f("f", "f", 0.5, 0., 1.);

   RooAddPdf model("model", "model", RooArgSet(gauss, poly), f);


   // Generate small dataset for use in fitting below

   std::unique_ptr<RooDataSet> d{model.generate(x, 50)};


   // C r e a t e   c o n s t r a i n t   p d f

   // -----------------------------------------


   // Construct Gaussian constraint pdf on parameter f at 0.8 with resolution of 0.1

   RooGaussian fconstraint("fconstraint", "fconstraint", f, 0.8, 0.2);


   // 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

   // -------------------------------------------------------------------------------------


   // Multiply constraint term with regular pdf using RooProdPdf

   // Specify in fitTo() that internal constraints on parameter f should be used


   // Multiply constraint with pdf

   RooProdPdf modelc("modelc", "model with constraint", RooArgSet(model, fconstraint));


   // Fit model (without use of constraint term)

   std::unique_ptr<RooFitResult> r1{model.fitTo(*d, Save(), PrintLevel(-1))};


   // Fit modelc with constraint term on parameter f

   std::unique_ptr<RooFitResult> r2{modelc.fitTo(*d, Constrain(f), Save(), PrintLevel(-1))};


   // 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

   // -------------------------------------------------------------------------------------------------------


   // Construct another Gaussian constraint pdf on parameter f at 0.2 with resolution of 0.1

   RooGaussian fconstext("fconstext", "fconstext", f, 0.2, 0.1);


   // Fit with external constraint

   std::unique_ptr<RooFitResult> r3{model.fitTo(*d, ExternalConstraints(fconstext), Save(), PrintLevel(-1))};


   // Print the fit results

   cout << "fit result without constraint (data generated at f=0.5)" << endl;

   r1->Print("v");

   cout << "fit result with internal constraint (data generated at f=0.5, constraint is f=0.8+/-0.2)" << endl;

   r2->Print("v");

   cout << "fit result with (another) external constraint (data generated at f=0.5, constraint is f=0.2+/-0.1)" << endl;

   r3->Print("v");

}

d
#define d(i)
Definition RSha256.hxx:102

f
#define f(i)
Definition RSha256.hxx:104

RooAddPdf.h

RooDataSet.h

RooFitResult.h

RooGaussian.h

RooPlot.h

RooPolynomial.h

RooProdPdf.h

RooRealVar.h

TAxis.h

TCanvas.h

TH1.h

RooAddPdf
Efficient implementation of a sum of PDFs of the form.
Definition RooAddPdf.h:33

RooArgSet
RooArgSet is a container object that can hold multiple RooAbsArg objects.
Definition RooArgSet.h:24

RooGaussian
Plain Gaussian p.d.f.
Definition RooGaussian.h:24

RooPolynomial
RooPolynomial implements a polynomial p.d.f of the form.
Definition RooPolynomial.h:25

RooProdPdf
Efficient implementation of a product of PDFs of the form.
Definition RooProdPdf.h:39

RooRealVar
Variable that can be changed from the outside.
Definition RooRealVar.h:37

RooFit::Constrain
RooCmdArg Constrain(const RooArgSet &params)
Definition RooGlobalFunc.cxx:661

RooFit::Save
RooCmdArg Save(bool flag=true)
Definition RooGlobalFunc.cxx:611

RooFit::ExternalConstraints
RooCmdArg ExternalConstraints(const RooArgSet &constraintPdfs)
Definition RooGlobalFunc.cxx:683

RooFit::PrintLevel
RooCmdArg PrintLevel(Int_t code)
Definition RooGlobalFunc.cxx:619

x
Double_t x[n]
Definition legend1.C:17

RooFit
The namespace RooFit contains mostly switches that change the behaviour of functions of PDFs (or othe...
Definition CodegenImpl.h:64

rf604_constraints
Definition rf604_constraints.py:1

m
TMarker m
Definition textangle.C:8