RDF: read trees from multiple TDirectories in the same file

[mpuccio]

Hello,

the output of the grid jobs in ALICE consists often of several TDirectories containing the output trees obtained on different chunks of data (being a new user I cannot put links to an example file). In order to easily process all these trees with RDataFrame, I usually merge all of them into a single TTree, but I am wondering if there is an easy interface that I could use, something like:

ROOT::RDataFrame d("O2zdcsptable", "AO2D.root:DF*/");

or

ROOT::RDataFrame d("DF*/O2zdcsptable", "AO2D.root");

(I tried these two, and they don’t work). Sorry if I am missing something trivial, but I could not find it easily in the documentation.

Thanks a lot!
Maximiliano

[Danilo]

Hi Maximiliano,

Thanks for the interesting post and welcome to the ROOT community!
I think we do not support this kind of wildcards.
A proposal to unblock you: why not building a TChain made of all these TTrees and then a RDF instance initialised with the aforementioned chain?

I hope this helps.

Best,
D

[mpuccio]

Hi Danilo,

thanks a lot for the reply! I am trying with the TChain, do you know if there a wildcard expansion for the TDirectories in TChain::Add? It works for files, but I tried c.Add("AO2D.root?#*/O2nucleitablemc") and it did not work.

Thanks again!
Cheers,
Max

[Danilo]

Hi Max,

I think we do not provide this functionality for TChains.

Cheers,
Danilo