 ROOT   Reference Guide rf103_interprfuncs.C
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1 /// \file
2 /// \ingroup tutorial_roofit
3 /// \notebook -js
4 ///
5 ///
6 /// \brief Basic functionality: interpreted functions and PDFs.
7 ///
8 /// \macro_image
9 /// \macro_output
10 /// \macro_code
11 ///
12 /// \date 07/2008
13 /// \author Wouter Verkerke
14
15 #include "RooRealVar.h"
16 #include "RooDataSet.h"
17 #include "RooGaussian.h"
18 #include "TCanvas.h"
19 #include "TAxis.h"
20 #include "RooPlot.h"
21 #include "RooFitResult.h"
22 #include "RooGenericPdf.h"
23 #include "RooConstVar.h"
24
25 using namespace RooFit;
26
27 void rf103_interprfuncs()
28 {
29  // ----------------------------------------------------
30  // G e n e r i c i n t e r p r e t e d p . d . f .
31  // ====================================================
32
33  // Declare observable x
34  RooRealVar x("x", "x", -20, 20);
35
36  // C o n s t r u c t g e n e r i c p d f f r o m i n t e r p r e t e d e x p r e s s i o n
37  // -------------------------------------------------------------------------------------------------
38
39  // To construct a proper p.d.f, the formula expression is explicitly normalized internally by dividing
40  // it by a numeric integral of the expression over x in the range [-20,20]
41  //
42  RooRealVar alpha("alpha", "alpha", 5, 0.1, 10);
43  RooGenericPdf genpdf("genpdf", "genpdf", "(1+0.1*abs(x)+sin(sqrt(abs(x*alpha+0.1))))", RooArgSet(x, alpha));
44
45  // S a m p l e , f i t a n d p l o t g e n e r i c p d f
46  // ---------------------------------------------------------------
47
48  // Generate a toy dataset from the interpreted p.d.f
49  RooDataSet *data = genpdf.generate(x, 10000);
50
51  // Fit the interpreted p.d.f to the generated data
52  genpdf.fitTo(*data);
53
54  // Make a plot of the data and the p.d.f overlaid
55  RooPlot *xframe = x.frame(Title("Interpreted expression pdf"));
56  data->plotOn(xframe);
57  genpdf.plotOn(xframe);
58
59  // -----------------------------------------------------------------------------------------------------------
60  // S t a n d a r d p . d . f a d j u s t w i t h i n t e r p r e t e d h e l p e r f u n c t i o n
61  // ==========================================================================================================
62  // Make a gauss(x,sqrt(mean2),sigma) from a standard RooGaussian
63
64  // C o n s t r u c t s t a n d a r d p d f w i t h f o r m u l a r e p l a c i n g p a r a m e t e r
65  // ------------------------------------------------------------------------------------------------------------
66
67  // Construct parameter mean2 and sigma
68  RooRealVar mean2("mean2", "mean^2", 10, 0, 200);
69  RooRealVar sigma("sigma", "sigma", 3, 0.1, 10);
70
71  // Construct interpreted function mean = sqrt(mean^2)
72  RooFormulaVar mean("mean", "mean", "sqrt(mean2)", mean2);
73
74  // Construct a gaussian g2(x,sqrt(mean2),sigma) ;
75  RooGaussian g2("g2", "h2", x, mean, sigma);
76
77  // G e n e r a t e t o y d a t a
78  // ---------------------------------
79
80  // Construct a separate gaussian g1(x,10,3) to generate a toy Gaussian dataset with mean 10 and width 3
81  RooGaussian g1("g1", "g1", x, RooConst(10), RooConst(3));
82  RooDataSet *data2 = g1.generate(x, 1000);
83
84  // F i t a n d p l o t t a i l o r e d s t a n d a r d p d f
85  // -------------------------------------------------------------------
86
87  // Fit g2 to data from g1
88  RooFitResult *r = g2.fitTo(*data2, Save());
89  r->Print();
90
91  // Plot data on frame and overlay projection of g2
92  RooPlot *xframe2 = x.frame(Title("Tailored Gaussian pdf"));
93  data2->plotOn(xframe2);
94  g2.plotOn(xframe2);
95
96  // Draw all frames on a canvas
97  TCanvas *c = new TCanvas("rf103_interprfuncs", "rf103_interprfuncs", 800, 400);
98  c->Divide(2);
99  c->cd(1);
101  xframe->GetYaxis()->SetTitleOffset(1.4);
102  xframe->Draw();
103  c->cd(2);
105  xframe2->GetYaxis()->SetTitleOffset(1.4);
106  xframe2->Draw();
107 }
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
TObject::Print
virtual void Print(Option_t *option="") const
This method must be overridden when a class wants to print itself.
Definition: TObject.cxx:552
r
ROOT::R::TRInterface & r
Definition: Object.C:4
RooGaussian.h
x
Double_t x[n]
Definition: legend1.C:17
RooGaussian
Plain Gaussian p.d.f.
Definition: RooGaussian.h:25
TCanvas.h
RooGenericPdf.h
RooDataSet.h
RooFitResult
RooFitResult is a container class to hold the input and output of a PDF fit to a dataset.
Definition: RooFitResult.h:40
RooFormulaVar
A RooFormulaVar is a generic implementation of a real-valued object, which takes a RooArgList of serv...
Definition: RooFormulaVar.h:30
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
RooFitResult.h
RooConstVar.h
sigma
const Double_t sigma
Definition: h1analysisProxy.h:11
TCanvas
The Canvas class.
Definition: TCanvas.h:23
TAxis.h
RooGenericPdf
RooGenericPdf is a concrete implementation of a probability density function, which takes a RooArgLis...
Definition: RooGenericPdf.h:25
rf103_interprfuncs
Definition: rf103_interprfuncs.py:1
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:36
RooFit::Save
RooCmdArg Save(Bool_t flag=kTRUE)
Definition: RooGlobalFunc.cxx:187
RooFit::Title
RooCmdArg Title(const char *name)
Definition: RooGlobalFunc.cxx:173
RooArgSet
RooArgSet is a container object that can hold multiple RooAbsArg objects.
Definition: RooArgSet.h:28
RooFit::RooConst
RooConstVar & RooConst(Double_t val)
Definition: RooGlobalFunc.cxx:341