rf604_constraints.C: 'LIKELIHOOD AND MINIMIZATION' RooFit tutorial macro #604
/////////////////////////////////////////////////////////////////////////
//
// 'LIKELIHOOD AND MINIMIZATION' RooFit tutorial macro #604
//
// Fitting with constraints
//
//
// 07/2008 - Wouter Verkerke
//
/////////////////////////////////////////////////////////////////////////
#ifndef __CINT__
#include "RooGlobalFunc.h"
#endif
#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 "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 p.d.f
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 p.d.f (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
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 p.d.f on parameter f at 0.8 with resolution of 0.1
RooGaussian fconstraint("fconstraint","fconstraint",f,RooConst(0.8),RooConst(0.1)) ;
// 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 p.d.f using RooProdPdf
// Specify in fitTo() that internal constraints on parameter f should be used
// Multiply constraint with p.d.f
RooProdPdf modelc("modelc","model with constraint",RooArgSet(model,fconstraint)) ;
// Fit modelc without use of constraint term
RooFitResult* r1 = modelc.fitTo(*d,Save()) ;
// Fit modelc with constraint term on parameter f
RooFitResult* r2 = modelc.fitTo(*d,Constrain(f),Save()) ;
// 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 p.d.f on parameter f at 0.8 with resolution of 0.1
RooGaussian fconstext("fconstext","fconstext",f,RooConst(0.2),RooConst(0.1)) ;
// Fit with external constraint
RooFitResult* r3 = model.fitTo(*d,ExternalConstraints(fconstext),Save()) ;
// 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") ;
}
Last change: Wed Dec 17 10:56:34 2008
Last generated: 2008-12-17 10:56
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