TChain with histogram

Dear experts,
I have many big root files, but I want to get only a few histograms. Is there a tool like TChain that is working with histograms?

What do you want to do exactly ? TChain allows to analyse a TTree spread over several ROOT files. With trees it makes sense: The number of events to analyse is only bigger with several files than with one file. But with histograms I do not see how to “chains” them ?

Dear Couet,
I have many root files, but I need to analyse the histograms. I wanted to copy only the directories that I want into a new file, then merge these light root files, but these can’t work because rootcp doe not keep the same structure. Do you see another solution to do that as TChain will not work?

Are you looking for hadd -T output.root inputs...? i.e. add all histograms but ignore trees?

Dear behrenhoff,
I do not want to add all the hist. Only the one which are in a specific directory.

May be you can have the reverse approach: make a full copy of the file (rootcp) and in that copy remove what you do not need (rootrm) .

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