[ROOT] Another Question about Trees

From: mark.winkler@philips.com
Date: Thu Jun 12 2003 - 21:00:33 MEST


Hello Rooters,

Could someone spell out the relationship between TFile and TTree classes? 
My motivation in asking is a desire to read from an existing tree, process 
some data, write results to a separate (previously non-existent) tree, and 
then go back to reading from tree 1 in order to repeat -- thus several 
trees would be open at the same time -- all of which "belong" to different 
files.

  I am a little unclear how a tree gets "linked" to a given file.  Reading 
seems fairly intuitive:  open a file, then "Get" part of that file with 
the name of the tree.  However, writing seems like a bit of a mystery to 
me: declare a file, and then the first tree declared after it is "its" 
tree?

I know the forum desires specific problems with code/etc.-- my apologies 
in advance to any offended!

Thanks!
Mark



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