Hi, If I understood it correctly; you want to chain 4 root files, say file1.root, file2.root, file3.root, and file4.root, then you want to produce a code using the MakeClass Functionality. If this is the case, one possibility is: At the directory where all these root files are located do: root[] TChain ch("SMT"); root[] ch.Add("file*.root"); root[] SMT->MakeClass("myClass"); Assuming the root files are of same tree structure, the above lines should result to the creatioin of myClass.C and myClass.h. Then you can edit/modify the files according the nature of your application. I you want to understand the meaning of the codes and functions in the TChain class I suggest you go to the site: http://root.cern.ch/root/html/TChain.html Hope it helps...keep trying. On Sun, 17 Aug 2003, Justace Clutter wrote: > I am a very new root user and have been trying to understand how the TChain > works. There is a TTree, called SMT, spread out among four different root > files. If I load the first file up using just a straight TFile I can access > the data directly like the following: > > Int_t fdisk01_wedge01_n[768]; > > SMT->SetBranchAddress("fdisk01_wedge01_n", &fdisk01_wedge01_n); > SMT->GetEntry(0); > > However when I try to load all the data at once with TChain I get very > confused. > > TChain *data_chain = new TChain("SMT"); > > data_chain->Add("file1"); > data_chain->Add("file2"); > data_chain->Add("file3"); > data_chain->Add("file4"); > > At this point I can not just run the same code as I did above. Now I ran the > makeclass utilities and generated the class files, but now I am even more > confused. The variables are declared in the class but only a few are set > through the SetBranchAddress functions. But they are all available somehow. > > I know that this post is very confusing, but I am confused. I have went > through the ROOT Users Guide and the examples but they did not help my > understanding of this. Any help on this matter would be greatly appreciated. > I guess that I just want to know how it works, I could just use the makeclass > and close my eyes but that does not put a smile on my face. > > Justace Clutter > -- -------------------------------------------------------- Zaldy A. Nawang PS Users Room 2 Yon Gokan, E362, Neutrino Group, IPNS, KEK, Japan e-mail: zaldy@neutrino.kek.jp Tel. No. : (81) 029864 - 5387 --------------------------------------------------------
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