Read and draw RooDataHist

[renqipan]

Hi experts,
I have a RooWorkSpace “w” storied in a root file and inside the RooWorkSpace it has several RooDataHist, How can I read and draw these RooDataHist? I try as following, but it can’t work.
Thank you
Best regards

RooAbsData *aterm_hist=w->data(“ttbar_Atermdatahist”);
RooPlot *plotmhist=w->var(“mass_tt”)->frame();
aterm_hist->plotOn(plotmhist, RooFit::LineColor(kBlack),RooFit::LineWidth(1));

[StephanH]

Why doesn’t it work? Any error messages?

What you do looks correct at first sight, but you also need something like
plotmhist->Draw().

[renqipan]

Hi,
when run the code it encounter error, it says:
warning: null passed to a callee that requires a non-null argument [-Wnonnull].
It seems the code didn’t read the RooDataHist in.

[StephanH]

Ok, you got a nullptr from one of the functions. Please check which pointer is invalid before you use it.