{
    RooRealVar x("x","var x",0.,1.);
    RooRealVar y("y","var y",-5.,+5.);
    RooCategory c("c","charge");
    c.defineType("Plus",+1);
    c.defineType("Minus",-1);
    
    RooDataSet data("data","data",RooArgSet(x,y,c));
    
    TRandom3 rnd;
    for (int i=0; i<1000; i++) {
        x.setVal(rnd.Uniform());
        y.setVal(rnd.Gaus());
        if (rnd.Uniform()<0.5) c.setLabel("Plus");
            else c.setLabel("Minus");
        data.add(RooArgSet(x,y,c));
    }
    data.Print("v");
}