Logo ROOT  
Reference Guide
No Matches
Go to the documentation of this file.
1/// \file
2/// \ingroup tutorial_roofit
3/// \notebook -js
4/// Basic functionality: interpreted functions and PDFs.
6/// \macro_image
7/// \macro_output
8/// \macro_code
10/// \date July 2008
11/// \author Wouter Verkerke
13#include "RooRealVar.h"
14#include "RooDataSet.h"
15#include "RooGaussian.h"
16#include "TCanvas.h"
17#include "TAxis.h"
18#include "RooPlot.h"
19#include "RooFitResult.h"
20#include "RooGenericPdf.h"
21#include "RooConstVar.h"
23using namespace RooFit;
27 // ----------------------------------------------------
28 // G e n e r i c i n t e r p r e t e d p . d . f .
29 // ====================================================
31 // Declare observable x
32 RooRealVar x("x", "x", -20, 20);
34 // 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
35 // -------------------------------------------------------------------------------------------------
37 // To construct a proper pdf, the formula expression is explicitly normalized internally by dividing
38 // it by a numeric integral of the expression over x in the range [-20,20]
39 //
40 RooRealVar alpha("alpha", "alpha", 5, 0.1, 10);
41 RooGenericPdf genpdf("genpdf", "genpdf", "(1+0.1*abs(x)+sin(sqrt(abs(x*alpha+0.1))))", RooArgSet(x, alpha));
43 // 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
44 // ---------------------------------------------------------------
46 // Generate a toy dataset from the interpreted pdf
47 RooDataSet *data = genpdf.generate(x, 10000);
49 // Fit the interpreted pdf to the generated data
50 genpdf.fitTo(*data);
52 // Make a plot of the data and the pdf overlaid
53 RooPlot *xframe = x.frame(Title("Interpreted expression pdf"));
54 data->plotOn(xframe);
55 genpdf.plotOn(xframe);
57 // -----------------------------------------------------------------------------------------------------------
58 // 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
59 // ==========================================================================================================
60 // Make a gauss(x,sqrt(mean2),sigma) from a standard RooGaussian
62 // 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
63 // ------------------------------------------------------------------------------------------------------------
65 // Construct parameter mean2 and sigma
66 RooRealVar mean2("mean2", "mean^2", 10, 0, 200);
67 RooRealVar sigma("sigma", "sigma", 3, 0.1, 10);
69 // Construct interpreted function mean = sqrt(mean^2)
70 RooFormulaVar mean("mean", "mean", "sqrt(mean2)", mean2);
72 // Construct a gaussian g2(x,sqrt(mean2),sigma) ;
73 RooGaussian g2("g2", "h2", x, mean, sigma);
75 // G e n e r a t e t o y d a t a
76 // ---------------------------------
78 // Construct a separate gaussian g1(x,10,3) to generate a toy Gaussian dataset with mean 10 and width 3
79 RooGaussian g1("g1", "g1", x, RooConst(10), RooConst(3));
80 RooDataSet *data2 = g1.generate(x, 1000);
82 // 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
83 // -------------------------------------------------------------------
85 // Fit g2 to data from g1
86 RooFitResult *r = g2.fitTo(*data2, Save());
87 r->Print();
89 // Plot data on frame and overlay projection of g2
90 RooPlot *xframe2 = x.frame(Title("Tailored Gaussian pdf"));
91 data2->plotOn(xframe2);
92 g2.plotOn(xframe2);
94 // Draw all frames on a canvas
95 TCanvas *c = new TCanvas("rf103_interprfuncs", "rf103_interprfuncs", 800, 400);
96 c->Divide(2);
97 c->cd(1);
98 gPad->SetLeftMargin(0.15);
99 xframe->GetYaxis()->SetTitleOffset(1.4);
100 xframe->Draw();
101 c->cd(2);
102 gPad->SetLeftMargin(0.15);
103 xframe2->GetYaxis()->SetTitleOffset(1.4);
104 xframe2->Draw();
ROOT::R::TRInterface & r
Definition Object.C:4
#define c(i)
Definition RSha256.hxx:101
#define gPad
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
RooArgSet is a container object that can hold multiple RooAbsArg objects.
Definition RooArgSet.h:29
RooDataSet is a container class to hold unbinned data.
Definition RooDataSet.h:33
RooFitResult is a container class to hold the input and output of a PDF fit to a dataset.
A RooFormulaVar is a generic implementation of a real-valued object, which takes a RooArgList of serv...
Plain Gaussian p.d.f.
Definition RooGaussian.h:24
RooGenericPdf is a concrete implementation of a probability density function, which takes a RooArgLis...
A RooPlot is a plot frame and a container for graphics objects within that frame.
Definition RooPlot.h:44
TAxis * GetYaxis() const
Definition RooPlot.cxx:1263
static RooPlot * frame(const RooAbsRealLValue &var, Double_t xmin, Double_t xmax, Int_t nBins)
Create a new frame for a given variable in x.
Definition RooPlot.cxx:249
virtual void Draw(Option_t *options=0)
Draw this plot and all of the elements it contains.
Definition RooPlot.cxx:691
RooRealVar represents a variable that can be changed from the outside.
Definition RooRealVar.h:39
virtual void SetTitleOffset(Float_t offset=1)
Set distance between the axis and the axis title.
Definition TAttAxis.cxx:293
The Canvas class.
Definition TCanvas.h:23
virtual void Print(Option_t *option="") const
This method must be overridden when a class wants to print itself.
Definition TObject.cxx:552
RooConstVar & RooConst(Double_t val)
RooCmdArg Save(Bool_t flag=kTRUE)
const Double_t sigma
Double_t x[n]
Definition legend1.C:17
The namespace RooFit contains mostly switches that change the behaviour of functions of PDFs (or othe...
const char * Title
Definition TXMLSetup.cxx:68