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RooDataHist over/underflow

Dear experts,

I have a question concerning the handling of over- and underflow when using a RooDataHist. My ROOT version is 6.18, but I also tested the behaviour with 6.20.

I am importing a TH2D histogram via RooDataHist and plot the projection of the RooDataHist on the x axis.
It seems to me like this projection does not account for over- and underlow bins that are present in the initial TH2D.
To illustrate this behaviour, I can alternatively first create a projection of the TH2D on the x axis via the method Projectionx(), giving me a TH1D which fully accounts for the over- and underflow. I then import this TH1D via RooDataHist and compare it to the first projection.

Please find a simplified test example below:

 TH2D *h2 = new TH2D("h2", "", 2, 0, 2, 2, 0, 2);
 h2->Fill(0.5, 0.5);
 h2->Fill(1.5, 1.5);
 h2->Fill(0.5, -1);
 h2->Fill(0.5, -1);
 RooRealVar x("x", "x", -10, 10);
 RooRealVar y("y", "y", -10, 10);
 RooDataHist *dataHist = new RooDataHist("dataHist", "dataHist", RooArgList(x, y), h2);
 TH1D *h1_x = h2->ProjectionX("projX");
 RooDataHist *dataHist_x = new RooDataHist("dataHist_x", "dataHist_x", x, h1_x);
 RooPlot* frame = x.frame();
 dataHist_x->plotOn(frame, LineColor(kRed+2));

The 2 points in the x-y space at (0.5, -1) are not visible in the projection of the 2D RooDataHist.

Do I need to specify an additional option when calling plotOn() to account for the over- and underflow? Can I assume that the over- and underflow is in principle correctly accounted for when importing a 2D histogram through RooDataHist?

Your help is highly appreciated.

Best regards,

May be @moneta has an idea.