ProjectRange doesn't work for RooHistPdf

[11117]

Dear colleagues,

I’m trying to project multidimensional RooHistPdf while integrating over a specific range of other variable: exactly what is shown at RooFit tutorial macro #310 but with RooHistPdf as a model.
Unfortunately, the model doesn’t catch normalization properly.
See the minimal working example (code and problematic output) attached.

Could you please help me to get normalization properly?
(I’m using RooFit v3.60)

Bad_Fit.pdf (23.0 KB) min_example.C (4.1 KB)

[Axel]

Hi,

We need our RooFit expert @StephanH to be back to answer your question. He should return from travel next week; please ping here should you not get an answer by end of next week!

Axel.

[11117]

Hi @Axel, thanks for the reply. Will do.

[11117]

Hi @StephanH, sorry for bothering you, but @Axel suggested to ping you to point at this question.
Do you have may be any ideas how to fix RooFit behaviour here?

[StephanH]

Hi @11117,

I ran it with debugger etc, but I have no clue why it doesn’t work out the integral correctly. I will try to ask Wouter Verkerke about it.

[11117]

Thanks Stephan. Let’s wait for Wouter’s response than.

(Sorry for the awkward nickname - I’m Ilya).

[adam.davis]

+1 so this doesn’t get closed

[StephanH]

Hi,

it looks like there is a bug in computing the relevant integrals, but there’s apparently a way around it:

1. Create a dataset that only contains events in the signal range (that happens anyway for plotting, so you can create it once, and also use it for plotting).
2. Ask for a data-weighted projection, i.e. project out the curve only at the locations indicated by the data points in the sample.

It’s done in this tutorial
https://root.cern.ch/doc/master/rf316__llratioplot_8C.html
and the relevant lines should look something like

auto projData = static_cast<RooDataSet*>(mcprojData->reduce(Cut("<signalRegionCuts>"))); //Probably CutRange(const char* name) also works
model.plotOn(frame2, ProjWData(*projData));

[StephanH]

auto projData = static_cast<RooDataSet*>(data->reduce(CutRange("sigRegion")));
   projData->plotOn(frame2_hist);
   model_hist.plotOn(frame2_hist, ProjWData(*projData), LineColor(kRed));

[11117]

Thanks, @StephanH!
This solution works for the example, but there are some problems when I try to use it in “real” code
(I have big 7D sample and ProjWData doesn’t seem to scale there). But this is another business - let me investigate my own issues in detail and open another topic if needed.

[StephanH]

Yeah, it’s slow unfortunately. Maybe Wouter finds the bug that sparked your question in the mean time.

[jonas]

This problem, which was tracked in JIRA issue ROOT-10483 got resolved with the 6.24 release.