Entry$ in TChain::Draw


It looks like (v3.10/02) the Entry$ variable of the TTree::Draw is the index of an event in a tree, but that it resetted for each new TTree in a TChain.

For my own experience, I would think it is much more useful to have it continuous from 0 to Entries$-1 (Entries$ refers to the entierety of the TChain) for interactive work.

Is there some other point of view ?

Best regards, Vincent.

Bonjour Vincent,

Beside the fact that it is harder (from TTreeFormula’s point of view) to get to the entry number within the chain than within the tree, it also is a less concrete/stable concept. It would be even harder to retrieve that value if you were to use PROOF to analyze your chain.

(In other word, this might be possible to do but at some significant development cost and possibly some run-time cost. Hence unless there are more requests for it (or unless you offer to implement it :slight_smile: ), it is unlikely to be changed in the near future).