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1/// \file
2/// \ingroup tutorial_fit
3/// \notebook -js
4/// Test generation of random numbers distributed according to a function defined by the user
6/// \macro_image
7/// \macro_output
8/// \macro_code
10/// \author Rene Brun
12void qa2() {
13 //Fill a 1-D histogram from a parametric function
14 TCanvas *c1 = new TCanvas("c1","The FillRandom example",0,0,700,500);
16 gBenchmark->Start("fillrandom");
17 //
18 // A function (any dimension) or a formula may reference
19 // an already defined formula
20 //
21 TFormula *form1 = new TFormula("form1","abs(sin(x)/x)");
22 TF1 *sqroot = new TF1("sqroot","x*gaus(0) + [3]*form1",0,10);
23 sqroot->SetParameters(10,4,1,20);
25 //
26 // Create a one dimensional histogram (one float per bin)
27 // and fill it following the distribution in function sqroot.
28 //
29 TH1F *h1f = new TH1F("h1f","Test random numbers",200,0,10);
30 h1f->SetFillColor(45);
31 h1f->FillRandom("sqroot",100000);
32 h1f->Draw();
33 TPaveLabel *lfunction = new TPaveLabel(5,39,9.8,46,"The sqroot function");
34 lfunction->SetFillColor(41);
36 c1->SetGridx();
37 c1->SetGridy();
39 h1f->SetDirectory(0);
41 c1->Update();
43 sqroot->SetParameters(200,4,1,20);
R__EXTERN TBenchmark * gBenchmark
Definition: TBenchmark.h:59
virtual void SetFillColor(Color_t fcolor)
Set the fill area color.
Definition: TAttFill.h:37
virtual void Start(const char *name)
Starts Benchmark with the specified name.
Definition: TBenchmark.cxx:172
The Canvas class.
Definition: TCanvas.h:23
1-Dim function class
Definition: TF1.h:213
virtual void SetParameters(const Double_t *params)
Definition: TF1.h:644
The Formula class.
Definition: TFormula.h:87
1-D histogram with a float per channel (see TH1 documentation)}
Definition: TH1.h:575
virtual void SetDirectory(TDirectory *dir)
By default when an histogram is created, it is added to the list of histogram objects in the current ...
Definition: TH1.cxx:8777
virtual void FillRandom(const char *fname, Int_t ntimes=5000, TRandom *rng=nullptr)
Fill histogram following distribution in function fname.
Definition: TH1.cxx:3525
virtual void Draw(Option_t *option="")
Draw this histogram with options.
Definition: TH1.cxx:3073
A Pave (see TPave) with a text centered in the Pave.
Definition: TPaveLabel.h:20
return c1
Definition: legend1.C:41