Is there any function to delete the data of specific rows in .root file?

[CY_Han]

In order to facilitate subsequent more complex data processing, I want to perform some preprocessing on the .root file. So, is there any function to delete the data of specific rows in .root file?

_ROOT Version: 6.24/02

[eguiraud]

Hi @CY_Han ,

there are some facilities, for example you can produce a TEntryList that contains the “good” rows and then always use that list of entries when reading the tree (e.g. TTreeReader has built-in support for TEntryLists).

The simplest thing you can do, however, is to produce a new filtered (“skimmed”) TTree that only contains the entries you want. It’s simple with RDataFrame:

ROOT::RDataFrame(treename, filename)
   .Filter("nMuon > 0") // select rows for which column nMuon > 0
   .Filter("Abs(Muon_eta) < 2.7")
   .Snapshot(newtreename, newfilename); // write a new tree in a new file

If you add a ROOT::EnableImplicitMT() at the top, this will run the skim in parallel on all your cores.

Cheers,
Enrico

[CY_Han]

Thanks for your reply, it works.