Test generation of random numbers distributed according to a function defined by the user

**Author:** Rene Brun

*This notebook tutorial was automatically generated with ROOTBOOK-izer from the macro found in the ROOT repository on Monday, March 27, 2023 at 09:47 AM.*

Fill a 1-D histogram from a parametric function

In [1]:

```
TCanvas *c1 = new TCanvas("c1","The FillRandom example",0,0,700,500);
gBenchmark->Start("fillrandom");
```

A function (any dimension) or a formula may reference an already defined formula

In [2]:

```
TFormula *form1 = new TFormula("form1","abs(sin(x)/x)");
TF1 *sqroot = new TF1("sqroot","x*gaus(0) + [3]*form1",0,10);
sqroot->SetParameters(10,4,1,20);
```

In [3]:

```
TH1F *h1f = new TH1F("h1f","Test random numbers",200,0,10);
h1f->SetFillColor(45);
h1f->FillRandom("sqroot",100000);
h1f->Draw();
TPaveLabel *lfunction = new TPaveLabel(5,39,9.8,46,"The sqroot function");
lfunction->SetFillColor(41);
c1->SetGridx();
c1->SetGridy();
h1f->SetDirectory(0);
c1->Update();
sqroot->SetParameters(200,4,1,20);
```

Draw all canvases

In [4]:

```
%jsroot on
gROOT->GetListOfCanvases()->Draw()
```