#include <RooWorkspace.h>
#include <RooRealVar.h>
#include <RooAbsPdf.h>
#include <RooDataSet.h>
#include <RooPlot.h>

void convolution () {
  RooWorkspace w("w", kTRUE);

  w.factory("Landau::landau(t[-10, 30], ml[5.0, -20, 20], sl[1, 0.1, 10])");
  w.factory("Gaussian::gauss(t, mg[0], sg[2, 0.1, 10])");

  // Construct convoluted pdf lxg(x) = landau(x) (*) gauss(x)
  // RooFFTConvPdf lxg("lxg", "landau X gauss", *w.var("t"), *w.pdf("landau"), *w.pdf("gauss"));

  // Alternative construction method using workspace
  w.factory("FCONV::lxg(t, landau, gauss)");

  // --- Generate a toyMC sample from composite PDF ---
  RooDataSet *data = w.pdf("lxg")->generate(*w.var("t"), 10000);

  // --- Perform fit
  w.pdf("lxg")->fitTo(*data);

  // --- Plot toy data and composite PDF overlaid ---
  RooPlot *frame = w.var("t")->frame();
  data->plotOn(frame);
  w.pdf("lxg")->plotOn(frame);
  w.pdf("landau")->plotOn(frame, RooFit::LineStyle(kDashed));

  frame->Draw();
} // convolution