rf203_ranges.C

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/// \file
/// \ingroup tutorial_roofit_main
/// \notebook -js
/// Fitting and plotting in sub ranges.
///
/// \macro_image
/// \macro_code
/// \macro_output
///
/// \date July 2008
/// \author Wouter Verkerke
 
#include "RooRealVar.h"
#include "RooDataSet.h"
#include "RooGaussian.h"
#include "RooPolynomial.h"
#include "RooAddPdf.h"
#include "RooFitResult.h"
#include "RooPlot.h"
#include "TCanvas.h"
#include "TAxis.h"
#include "TH1.h"
using namespace RooFit;
 
void rf203_ranges()
{
   // S e t u p   m o d e l
   // ---------------------
 
   // Construct observables x
   RooRealVar x("x", "x", -10, 10);
 
   // Construct gaussx(x,mx,1)
   RooRealVar mx("mx", "mx", 0, -10, 10);
   RooGaussian gx("gx", "gx", x, mx, 1.0);
 
   // Construct px = 1 (flat in x)
   RooPolynomial px("px", "px", x);
 
   // Construct model = f*gx + (1-f)px
   RooRealVar f("f", "f", 0., 1.);
   RooAddPdf model("model", "model", RooArgList(gx, px), f);
 
   // Generated 10000 events in (x,y) from pdf model
   std::unique_ptr<RooDataSet> modelData{model.generate(x, 10000)};
 
   // F i t   f u l l   r a n g e
   // ---------------------------
 
   // Fit pdf to all data
   std::unique_ptr<RooFitResult> r_full{model.fitTo(*modelData, Save(true), PrintLevel(-1))};
 
   // F i t   p a r t i a l   r a n g e
   // ----------------------------------
 
   // Define "signal" range in x as [-3,3]
   x.setRange("signal", -3, 3);
 
   // Fit pdf only to data in "signal" range
   std::unique_ptr<RooFitResult> r_sig{model.fitTo(*modelData, Save(true), Range("signal"), PrintLevel(-1))};
 
   // P l o t   /   p r i n t   r e s u l t s
   // ---------------------------------------
 
   // Make plot frame in x and add data and fitted model
   RooPlot *frame = x.frame(Title("Fitting a sub range"));
   modelData->plotOn(frame);
   model.plotOn(frame, Range(""), LineStyle(kDashed), LineColor(kRed)); // Add shape in full ranged dashed
   model.plotOn(frame);                                                     // By default only fitted range is shown
 
   // Print fit results
   cout << "result of fit on all data " << endl;
   r_full->Print();
   cout << "result of fit in in signal region (note increased error on signal fraction)" << endl;
   r_sig->Print();
 
   // Draw frame on canvas
   new TCanvas("rf203_ranges", "rf203_ranges", 600, 600);
   gPad->SetLeftMargin(0.15);
   frame->GetYaxis()->SetTitleOffset(1.4);
   frame->Draw();
 
   return;
}