TChain with TFriends

Good morning

I want to read in ~100 root files as a TChain, apply an MVA to the events and save only the MVA response in a branch in a new friend tree. This friend tree will then contain only the MVA response for all events in all 100 root files.

Is it guaranteed that when later reading in the original 100 root files again as a TChain and adding this friend tree to it that the correct MVA response will be matched with the correct event?

The original root files are large so I am essentially trying to avoid having to merge and re-save the events.

Many thanks


ROOT Version: 6.17.01
Platform: Not Provided
Compiler: Not Provided


If I understood correctly the number of events (and the order) in the original TTree and the new (friend) Tree are the same. If this is the case, indeed you are guaranteed that “when later reading in the original 100 root files again as a TChain and adding this friend tree to it that the correct MVA response will be matched with the correct event”

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