%%cpp -d
#include "RooRealVar.h"
#include "RooDataHist.h"
#include "RooGaussian.h"
#include "RooProdPdf.h"
#include "RooPolyVar.h"
#include "TH1.h"
#include "TCanvas.h"
#include "TAxis.h"
#include "RooPlot.h"
#include "RooNumIntConfig.h"
using namespace RooFit;

RooAbsPdf::defaultIntegratorConfig()->setEpsRel(1e-8);
RooAbsPdf::defaultIntegratorConfig()->setEpsAbs(1e-8);

RooRealVar x("x", "x", -5, 5);
RooRealVar y("y", "y", -2, 2);

RooRealVar a0("a0", "a0", 0);
RooRealVar a1("a1", "a1", -1.5, -3, 1);
RooPolyVar fy("fy", "fy", y, RooArgSet(a0, a1));

RooRealVar sigmax("sigmax", "width of gaussian", 0.5);
RooGaussian gaussx("gaussx", "Gaussian in x with shifting mean in y", x, fy, sigmax);

RooGaussian gaussy("gaussy", "Gaussian in y", y, 0.0, 2.0);

RooProdPdf model("model", "gaussx(x|y)*gaussy(y)", gaussy, Conditional(gaussx, x));

RooAbsPdf *modelx = model.createProjection(y);

std::unique_ptr<RooAbsData> data{modelx->generateBinned(x, 1000)};

modelx->fitTo(*data, Verbose(), PrintLevel(-1));

RooPlot *frame = x.frame(40);
data->plotOn(frame);
modelx->plotOn(frame);

TH1 *hh = model.createHistogram("x,y");
hh->SetLineColor(kBlue);

TCanvas *c = new TCanvas("rf315_projectpdf", "rf315_projectpdf", 800, 400);
c->Divide(2);
c->cd(1);
gPad->SetLeftMargin(0.15);
frame->GetYaxis()->SetTitleOffset(1.4);
frame->Draw();
c->cd(2);
gPad->SetLeftMargin(0.20);
hh->GetZaxis()->SetTitleOffset(2.5);
hh->Draw("surf");

gROOT->GetListOfCanvases()->Draw()