Weighted histogram using RDataFrame

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1

Hi all,

I was trying to make a weighted histogram using TTree vs RDataFrame, I followed the usual convention for TTree, tree->Draw(“x>>h(100,0,10)”,“weight*(cut)”)
vs RDataFrame auto h = df.Filter(“cut”).Histo1D({“h”,“h”,100,0,10},“x”, “weight”);

The integral of the 2 histograms are different, (dataframe value is lower). When I draw unweighted versions the numbers match.

Could someone pls point out the potential issue causing this.

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2

Hello,

Thanks for the post. I suspect the entries passing the two selections are different. Did you check that?
The RDF case is filtering based on the value of cut cast to a boolean.

Cheers,
Danilo

3

Hi Danilo,
The cuts are identical.
Cheers,
Nibir

4

Hi Nibir,

I do not understand. What is “cut” in your dataset? In the TTree::Draw snippet, are you maybe filling the histogram with a weight equal to 0 and not filling in the RDF case?

Cheers,
D

5

Hi Danilo, when weight = 0, it will be automatically ignored by the h->Integral function right.