Hi Christian, As soon as you have create your new trees and stored them in Newfile.root, close this file, call tree->AddFriend, open Newfile.root again in Update mode. Rene Brun On Sun, 20 Oct 2002, cstrato wrote: > Dear Rooters > > At the beginning of my program I open a file "OldFile.root", > which contains many trees, in READ mode, and I create a new > file "NewFile.root". > > Then I do the following: > 1. Get one tree from OldFile and add the other trees as friend. > 2. Do some calculation with the tree data > 3. Create new trees and store these trees in file NewFile.root > > However, at a later point I want to add one of the new trees, > stored in NewFile, as an additional friend to the existing > list of tree friends. > Sorrowly, the following line: > tree->AddFriend(aliasname, "/path/NewFile.root"); > or the line > tree->AddFriend(aliasname, "NewFile.root"); > creates the following error messages: > Warning in <TFile::Init>: file /path/NewFile.root has no keys > Warning in <TTree::AddFriend>: Unknown Tree alias=treename.exten > in file /path/NewFile.root > > My question is: > How can I add a newly created tree to an already existing list > of tree friends? > > Thank you in advance for your help. > > Best regards > Christian > _._._._._._._._._._._._._._._._ > C.h.i.s.t.i.a.n S.t.r.a.t.o.w.a > V.i.e.n.n.a A.u.s.t.r.i.a > _._._._._._._._._._._._._._._._ > >
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