{
  gROOT->SetStyle("Plain");

  RooRealVar x("x", "x", -10, 10);

  RooRealVar mu("mu", "average", 0, -1, 1);
  RooRealVar sigma("sigma", "r.m.s", 1, 0, 5);
  RooGaussian gauss("gauss","gaussian PDF", x, mu, sigma);

  RooRealVar lambda("lambda", "exponential slope", -0.1);
  RooExponential expo("expo", "exponential PDF", x, lambda);

  RooRealVar f("f", "gaussian fraction", 0.5, 0, 1);

  RooAddPdf sum("sum", "g + e", RooArgList(gauss, expo), RooArgList(f));

  RooPlot * xFrame = x.frame();
  sum.plotOn(xFrame, RooFit::LineColor(kRed)) ;
  sum.plotOn(xFrame, RooFit::Components("expo"), RooFit::LineColor(kBlue));
  TCanvas c;
  xFrame->Draw();
  c.SaveAs("02-gaussianPlusExpo.pdf");

  return 0;
}