rf105_funcbinding.C

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/// \file
/// \ingroup tutorial_roofit
/// \notebook -js
/// Basic functionality: binding ROOT math functions as RooFit functions and pdfs
///
/// \macro_image
/// \macro_output
/// \macro_code
/// \author 07/2008 - Wouter Verkerke

#include "RooRealVar.h"
#include "RooDataSet.h"
#include "RooGaussian.h"
#include "TCanvas.h"
#include "TAxis.h"
#include "RooPlot.h"
#include "TMath.h"
#include "TF1.h"
#include "Math/DistFunc.h"
#include "RooTFnBinding.h"

using namespace RooFit;

void rf105_funcbinding()
{

   // B i n d   T M a t h : : E r f   C   f u n c t i o n
   // ---------------------------------------------------

   // Bind one-dimensional TMath::Erf function as RooAbsReal function
   RooRealVar x("x", "x", -3, 3);
   RooAbsReal *errorFunc = bindFunction("erf", TMath::Erf, x);

   // Print erf definition
   errorFunc->Print();

   // Plot erf on frame
   RooPlot *frame1 = x.frame(Title("TMath::Erf bound as RooFit function"));
   errorFunc->plotOn(frame1);

   // B i n d   R O O T : : M a t h : : b e t a _ p d f   C   f u n c t i o n
   // -----------------------------------------------------------------------

   // Bind pdf ROOT::Math::Beta with three variables as RooAbsPdf function
   RooRealVar x2("x2", "x2", 0, 0.999);
   RooRealVar a("a", "a", 5, 0, 10);
   RooRealVar b("b", "b", 2, 0, 10);
   RooAbsPdf *beta = bindPdf("beta", ROOT::Math::beta_pdf, x2, a, b);

   // Perf beta definition
   beta->Print();

   // Generate some events and fit
   RooDataSet *data = beta->generate(x2, 10000);
   beta->fitTo(*data);

   // Plot data and pdf on frame
   RooPlot *frame2 = x2.frame(Title("ROOT::Math::Beta bound as RooFit pdf"));
   data->plotOn(frame2);
   beta->plotOn(frame2);

   // B i n d   R O O T   T F 1   a s   R o o F i t   f u n c t i o n
   // ---------------------------------------------------------------

   // Create a ROOT TF1 function
   TF1 *fa1 = new TF1("fa1", "sin(x)/x", 0, 10);

   // Create an observable
   RooRealVar x3("x3", "x3", 0.01, 20);

   // Create binding of TF1 object to above observable
   RooAbsReal *rfa1 = bindFunction(fa1, x3);

   // Print rfa1 definition
   rfa1->Print();

   // Make plot frame in observable, plot TF1 binding function
   RooPlot *frame3 = x3.frame(Title("TF1 bound as RooFit function"));
   rfa1->plotOn(frame3);

   TCanvas *c = new TCanvas("rf105_funcbinding", "rf105_funcbinding", 1200, 400);
   c->Divide(3);
   c->cd(1);
   gPad->SetLeftMargin(0.15);
   frame1->GetYaxis()->SetTitleOffset(1.6);
   frame1->Draw();
   c->cd(2);
   gPad->SetLeftMargin(0.15);
   frame2->GetYaxis()->SetTitleOffset(1.6);
   frame2->Draw();
   c->cd(3);
   gPad->SetLeftMargin(0.15);
   frame3->GetYaxis()->SetTitleOffset(1.6);
   frame3->Draw();
}