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rf109_chi2residpull.C
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1 /// \file
2 /// \ingroup tutorial_roofit
3 /// \notebook -js
4 /// Basic functionality: Calculating chi^2 from histograms and curves in RooPlots, making
5 /// histogram of residual and pull distributions
6 ///
7 /// \macro_image
8 /// \macro_output
9 /// \macro_code
10 ///
11 /// \date July 2008
12 /// \author Wouter Verkerke
13 
14 #include "RooRealVar.h"
15 #include "RooDataSet.h"
16 #include "RooGaussian.h"
17 #include "RooConstVar.h"
18 #include "TCanvas.h"
19 #include "TAxis.h"
20 #include "RooPlot.h"
21 #include "RooHist.h"
22 using namespace RooFit;
23 
24 void rf109_chi2residpull()
25 {
26 
27  // S e t u p m o d e l
28  // ---------------------
29 
30  // Create observables
31  RooRealVar x("x", "x", -10, 10);
32 
33  // Create Gaussian
34  RooRealVar sigma("sigma", "sigma", 3, 0.1, 10);
35  RooRealVar mean("mean", "mean", 0, -10, 10);
36  RooGaussian gauss("gauss", "gauss", x, RooConst(0), sigma);
37 
38  // Generate a sample of 1000 events with sigma=3
39  RooDataSet *data = gauss.generate(x, 10000);
40 
41  // Change sigma to 3.15
42  sigma = 3.15;
43 
44  // P l o t d a t a a n d s l i g h t l y d i s t o r t e d m o d e l
45  // ---------------------------------------------------------------------------
46 
47  // Overlay projection of gauss with sigma=3.15 on data with sigma=3.0
48  RooPlot *frame1 = x.frame(Title("Data with distorted Gaussian pdf"), Bins(40));
49  data->plotOn(frame1, DataError(RooAbsData::SumW2));
50  gauss.plotOn(frame1);
51 
52  // C a l c u l a t e c h i ^ 2
53  // ------------------------------
54 
55  // Show the chi^2 of the curve w.r.t. the histogram
56  // If multiple curves or datasets live in the frame you can specify
57  // the name of the relevant curve and/or dataset in chiSquare()
58  cout << "chi^2 = " << frame1->chiSquare() << endl;
59 
60  // S h o w r e s i d u a l a n d p u l l d i s t s
61  // -------------------------------------------------------
62 
63  // Construct a histogram with the residuals of the data w.r.t. the curve
64  RooHist *hresid = frame1->residHist();
65 
66  // Construct a histogram with the pulls of the data w.r.t the curve
67  RooHist *hpull = frame1->pullHist();
68 
69  // Create a new frame to draw the residual distribution and add the distribution to the frame
70  RooPlot *frame2 = x.frame(Title("Residual Distribution"));
71  frame2->addPlotable(hresid, "P");
72 
73  // Create a new frame to draw the pull distribution and add the distribution to the frame
74  RooPlot *frame3 = x.frame(Title("Pull Distribution"));
75  frame3->addPlotable(hpull, "P");
76 
77  TCanvas *c = new TCanvas("rf109_chi2residpull", "rf109_chi2residpull", 900, 300);
78  c->Divide(3);
79  c->cd(1);
80  gPad->SetLeftMargin(0.15);
81  frame1->GetYaxis()->SetTitleOffset(1.6);
82  frame1->Draw();
83  c->cd(2);
84  gPad->SetLeftMargin(0.15);
85  frame2->GetYaxis()->SetTitleOffset(1.6);
86  frame2->Draw();
87  c->cd(3);
88  gPad->SetLeftMargin(0.15);
89  frame3->GetYaxis()->SetTitleOffset(1.6);
90  frame3->Draw();
91 }
c
#define c(i)
Definition: RSha256.hxx:101
RooPlot::Draw
virtual void Draw(Option_t *options=0)
Draw this plot and all of the elements it contains.
Definition: RooPlot.cxx:691
RooPlot::residHist
RooHist * residHist(const char *histname=0, const char *pdfname=0, bool normalize=false, bool useAverage=kFALSE) const
Return a RooHist containing the residuals of histogram 'histname' with respect to curve 'curvename'.
Definition: RooPlot.cxx:1136
RooFit::Bins
RooCmdArg Bins(Int_t nbin)
Definition: RooGlobalFunc.cxx:177
RooAbsData::SumW2
@ SumW2
Definition: RooAbsData.h:97
RooFit::DataError
RooCmdArg DataError(Int_t)
Definition: RooGlobalFunc.cxx:157
RooGaussian.h
x
Double_t x[n]
Definition: legend1.C:17
RooGaussian
Plain Gaussian p.d.f.
Definition: RooGaussian.h:25
TCanvas.h
RooDataSet.h
RooPlot::chiSquare
Double_t chiSquare(int nFitParam=0) const
Shortcut for RooPlot::chiSquare(const char* pdfname, const char* histname, int nFitParam=0)
Definition: RooPlot.h:176
RooPlot::addPlotable
void addPlotable(RooPlotable *plotable, Option_t *drawOptions="", Bool_t invisible=kFALSE, Bool_t refreshNorm=kFALSE)
Add the specified plotable object to our plot.
Definition: RooPlot.cxx:570
TGeant4Unit::gauss
static constexpr double gauss
Definition: TGeant4SystemOfUnits.h:263
RooFit
The namespace RooFit contains mostly switches that change the behaviour of functions of PDFs (or othe...
Definition: RooCFunction1Binding.h:29
RooAbsData::plotOn
virtual RooPlot * plotOn(RooPlot *frame, const RooCmdArg &arg1=RooCmdArg::none(), const RooCmdArg &arg2=RooCmdArg::none(), const RooCmdArg &arg3=RooCmdArg::none(), const RooCmdArg &arg4=RooCmdArg::none(), const RooCmdArg &arg5=RooCmdArg::none(), const RooCmdArg &arg6=RooCmdArg::none(), const RooCmdArg &arg7=RooCmdArg::none(), const RooCmdArg &arg8=RooCmdArg::none()) const
Definition: RooAbsData.cxx:547
RooPlot.h
RooPlot::GetYaxis
TAxis * GetYaxis() const
Definition: RooPlot.cxx:1258
RooPlot
A RooPlot is a plot frame and a container for graphics objects within that frame.
Definition: RooPlot.h:44
RooRealVar.h
RooHist
A RooHist is a graphical representation of binned data based on the TGraphAsymmErrors class.
Definition: RooHist.h:27
RooHist.h
RooConstVar.h
RooPlot::pullHist
RooHist * pullHist(const char *histname=0, const char *pdfname=0, bool useAverage=false) const
Uses residHist() and sets normalize=true.
Definition: RooPlot.h:181
sigma
const Double_t sigma
Definition: h1analysisProxy.h:11
TCanvas
The Canvas class.
Definition: TCanvas.h:23
TAxis.h
gPad
#define gPad
Definition: TVirtualPad.h:287
RooDataSet
RooDataSet is a container class to hold unbinned data.
Definition: RooDataSet.h:33
TAttAxis::SetTitleOffset
virtual void SetTitleOffset(Float_t offset=1)
Set distance between the axis and the axis title.
Definition: TAttAxis.cxx:293
RooRealVar
RooRealVar represents a variable that can be changed from the outside.
Definition: RooRealVar.h:37
RooFit::Title
RooCmdArg Title(const char *name)
Definition: RooGlobalFunc.cxx:176
RooFit::RooConst
RooConstVar & RooConst(Double_t val)
Definition: RooGlobalFunc.cxx:347