{
    using namespace RooFit;
    
    // observable
    RooRealVar x("x", "random variable", 0.0, 1.0);
    
    // Gaussian model
    RooRealVar mu("mu", "mean parameter", 0.5, 0.0, 1.0);
    RooRealVar sigma("sigma", "width parameter", 0.1, 0.0, 0.3);
    RooGaussian gaus("gaus", "Gaussian PDF", x, mu, sigma);
    
    // Linear function: 1 + slope*x
    RooRealVar slope("slope", "slope parameter", -0.3, -10., 10.);
    RooPolynomial linear("linear", "Linear function", x, RooArgSet(slope));
    
    // add up: Gaussian + linear
    RooRealVar fraction("fraction","fraction of Gaussian",0.5,0.,1.);
    RooAddPdf model("model","PDF model", RooArgList(gaus,linear), RooArgList(fraction));
    
    // generate random data, plot
    RooDataSet *data = model.generate(x, 10000);
    RooPlot* frame = x.frame();
    data->plotOn(frame);
    model.plotOn(frame);
    model.plotOn(frame,Components(linear),LineStyle(7),LineColor(kRed));
    frame->Draw();
}