RooDataSet event iteration

Roofit and RooStats
1

Dear Roooters,

I have a quick question whether or not this piece of code is “correct” (or will do what I intend it to):

for(Int_t i=1; i < DecayTree->GetEntries(); i++)
{
	     RealDataHist->Fill((data2.get(i))->getRealValue("nSPDHits"),sData->GetSWeight(i,"nsig"));
	   }

data2 is RooDataSet created from the DecayTree TTree, sData is from RooStats::SPlot and RealDataHist is a normal TH1F* histogram. Because the histogram is specifically binned, I cant just create one the normal way from RooDataSet.
Will the iteration through the dataset work like this? Are they numbered from 0?
Sometimes the code returns the error message :
Error in : Trying to dereference null pointer or trying to call routine taking non-null arguments.
( for (data2.get(i)) )
and sometimes it just crashes. Any ideas?

EDIT:: I just checked and for a tree with 10.5k events the

(data2.get(i))->getRealValue("nSPDHits")

returns sensible values until around 8.5k event and then displays the error mentioned above.

Cheers,
Maks

2

Ok, I just found a solution (didnt know beforehand that RooDataSet inherits form RooAbsData) and the fillHistogram function does the job perfectly.

1 Like
3

This topic was automatically closed 14 days after the last reply. New replies are no longer allowed.