Use RDataFrame to skim a tree

[Wile_E_Coyote]

TTree::Draw control like "nentries" but for the output?

The “nentries” optional parameter for TTree::Draw is the number of entries from the tree which will be read, compared against the selection, and if passing, drawn. Is there a way to select the number of entries that will be drawn post-selection? E.g. if I have a TTree with 1000 entries, a selection argument, and I want the first 100 entries which pass the selection, can I get that via TTree::Draw? I can’t think of how to do it even with TEntryLists and such. More useful than an optional para…