/// \file /// \ingroup tutorial_roofit /// \notebook -nodraw /// /// Likelihood and minimization: fitting with constraints /// /// \macro_output /// \macro_code /// /// \date 07/2008 /// \author Wouter Verkerke #include "RooRealVar.h" #include "RooDataSet.h" #include "RooGaussian.h" #include "RooConstVar.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 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(0.2)); // 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 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 model (without use of constraint term) RooFitResult *r1 = model.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 0.2 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"); }