Concatenate RDataframe

ROOT
1

Hello, is there any features to concatenate two RDataframe (as pandas concatenate)?

This is my problem. I have a TTree with a branch called weight. I have to use this variables, but after dividing it by the sum of all the weight in the TTree. This is easily doable. The problem is that I have to use several input TTrees (from different files) and for each of them I have to consider the value of weight divided by the sum of the weight, where the sum of the weights is computed for each file (actually a bit more complicated since it is for group of files).

My workflow with pandas (via uproot) is:

  • load all the TTrees in different dataframes
  • for each TTree compute the sum of weights
  • add a new column, equal to the weight column divided by the sum
  • concatenate all the dataframes
2

Hi Ruggero,
I’m afraid RDataFrames do not concatenate.

I think the ROOT way would be to write friend trees with the computed weights/sum_of_weights per tree, and then add those trees as friends when you process everything together in a second step. Make sure to do this step in a single-thread or the output entries will be reshuffled w.r.t. to the input entries.

Cheers,
Enrico

3

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