%%cpp -d
#include "RooRealVar.h"
#include "RooDataSet.h"
#include "RooGaussian.h"
#include "RooConstVar.h"
#include "RooFormulaVar.h"
#include "RooProdPdf.h"
#include "RooEfficiency.h"
#include "RooPolynomial.h"
#include "RooCategory.h"
#include "TCanvas.h"
#include "TAxis.h"
#include "RooPlot.h"
using namespace RooFit;

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

RooRealVar a("a", "a", 0.4, 0, 1);
RooRealVar b("b", "b", 5);
RooRealVar c("c", "c", -1, -10, 10);
RooFormulaVar effFunc("effFunc", "(1-a)+a*cos((x-c)/b)", RooArgList(a, b, c, x));

RooCategory cut("cut", "cutr", { {"accept", 1}, {"reject", 0} });

RooEfficiency effPdf("effPdf", "effPdf", effFunc, cut, "accept");

RooPolynomial shapePdf("shapePdf", "shapePdf", x, RooConst(-0.095));
RooProdPdf model("model", "model", shapePdf, Conditional(effPdf, cut));

std::unique_ptr<RooDataSet> data{model.generate({x, cut}, 10000)};

effPdf.fitTo(*data, ConditionalObservables(x), PrintLevel(-1));

RooPlot *frame1 = x.frame(Bins(20), Title("Data (all, accepted)"));
data->plotOn(frame1);
data->plotOn(frame1, Cut("cut==cut::accept"), MarkerColor(kRed), LineColor(kRed));

RooPlot *frame2 = x.frame(Bins(20), Title("Fitted efficiency"));
data->plotOn(frame2, Efficiency(cut)); // needs ROOT version >= 5.21
effFunc.plotOn(frame2, LineColor(kRed));

TCanvas *ca = new TCanvas("rf701_efficiency", "rf701_efficiency", 800, 400);
ca->Divide(2);
ca->cd(1);
gPad->SetLeftMargin(0.15);
frame1->GetYaxis()->SetTitleOffset(1.6);
frame1->Draw();
ca->cd(2);
gPad->SetLeftMargin(0.15);
frame2->GetYaxis()->SetTitleOffset(1.4);
frame2->Draw();

%jsroot on
gROOT->GetListOfCanvases()->Draw()