Logo ROOT   6.21/01
Reference Guide
fillrandom.C File Reference

Detailed Description

View in nbviewer Open in SWAN Fill a 1-D histogram from a parametric function.

pict1_fillrandom.C.png
void fillrandom() {
TCanvas *c1 = new TCanvas("c1","The FillRandom example",200,10,700,900);
auto pad1 = new TPad("pad1","The pad with the function",0.05,0.50,0.95,0.95);
auto pad2 = new TPad("pad2","The pad with the histogram",0.05,0.05,0.95,0.45);
pad1->Draw();
pad2->Draw();
pad1->cd();
gBenchmark->Start("fillrandom");
//
// A function (any dimension) or a formula may reference
// an already defined formula
//
auto form1 = new TFormula("form1","abs(sin(x)/x)");
auto sqroot = new TF1("sqroot","x*gaus(0) + [3]*form1",0,10);
sqroot->SetParameters(10,4,1,20);
pad1->SetGridx();
pad1->SetGridy();
pad1->GetFrame()->SetBorderMode(-1);
pad1->GetFrame()->SetBorderSize(5);
sqroot->SetLineColor(4);
sqroot->SetLineWidth(6);
sqroot->Draw();
auto lfunction = new TPaveLabel(5,39,9.8,46,"The sqroot function");
lfunction->Draw();
c1->Update();
//
// Create a one dimensional histogram (one float per bin)
// and fill it following the distribution in function sqroot.
//
pad2->cd();
pad2->GetFrame()->SetBorderMode(-1);
pad2->GetFrame()->SetBorderSize(5);
auto h1f = new TH1F("h1f","Test random numbers",200,0,10);
h1f->SetFillColor(45);
h1f->FillRandom("sqroot",10000);
h1f->Draw();
c1->Update();
//
// Open a ROOT file and save the formula, function and histogram
//
TFile myfile("fillrandom.root","RECREATE");
form1->Write();
sqroot->Write();
h1f->Write();
gBenchmark->Show("fillrandom");
}
Author
Rene Brun

Definition in file fillrandom.C.