You could for example use a TChain:
If your files are small, you could also use the hadd tool to merge the root files before processing.
Or process files one by one and then use hadd to merge the resulting histograms.
You could for example use a TChain:
If your files are small, you could also use the hadd tool to merge the root files before processing.
Or process files one by one and then use hadd to merge the resulting histograms.