TCanvas *c1 = new TCanvas("c1","The FillRandom example",0,0,700,500);

gBenchmark->Start("fillrandom");

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);

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(nullptr);

c1->Update();

sqroot->SetParameters(200,4,1,20);

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