TChain

class TChain : public TTree

    public:

                  TChain TChain()
                  TChain TChain(const char* name, const char* title)
                  TChain TChain(TChain&)
            virtual void ~TChain()
            virtual void Add(const char* name, Int_t nentries = -1)
            virtual void Browse(TBrowser* b)
          static TClass* Class()
            virtual void CreatePackets()
            virtual void Draw(Option_t* opt)
            virtual void Draw(TCut varexp, TCut selection, Option_t* option, Int_t nentries = 1000000000, Int_t firstentry = 0)
            virtual void Draw(const char* varexp, const char* selection, Option_t* option, Int_t nentries = 1000000000, Int_t firstentry = 0)
        virtual TBranch* GetBranch(const char* name)
           virtual Int_t GetEntry(Int_t entry = 0, Int_t getall = 0)
                  TFile* GetFile()
          virtual TLeaf* GetLeaf(const char* name)
      virtual TObjArray* GetListOfBranches()
              TObjArray* GetListOfFiles()
      virtual TObjArray* GetListOfLeaves()
         virtual Float_t GetMaximum(const char* columname)
         virtual Float_t GetMinimum(const char* columname)
           virtual Int_t GetNbranches()
                TObject* GetNotify()
           virtual Int_t GetNtrees()
                  TList* GetStatus()
          virtual TTree* GetTree()
                   Int_t GetTreeNumber()
                  Int_t* GetTreeOffset()
           virtual Int_t GetTreeOffsetLen()
         virtual TClass* IsA() const
           virtual Int_t LoadTree(Int_t entry)
            virtual void Loop(Option_t* option, Int_t nentries = 1000000000, Int_t firstentry = 0)
            virtual void ls(Option_t* option)
            virtual void Merge(const char* name)
            virtual void Merge(TFile* file, Int_t basketsize, Option_t* option)
            virtual void Print(Option_t* option)
            virtual void SetBranchAddress(const char* bname, void* add)
            virtual void SetBranchStatus(const char* bname, Bool_t status = 1)
            virtual void SetNotify(TObject* obj)
            virtual void SetPacketSize(Int_t size = 100)
            virtual void ShowMembers(TMemberInspector& insp, char* parent)
            virtual void Streamer(TBuffer& b)

  Data Members

    protected:

           Int_t fTreeOffsetLen  Current size of fTreeOffset array
           Int_t fNtrees         Number of Trees
           Int_t fTreeNumber     Current Tree number in fTreeOffset table
           Int_t fNbranches      Number of branches in associated Tree
          Int_t* fTreeOffset     Array of variables
          TTree* fTree           Pointer to current tree
          TFile* fFile           Pointer to current file
      TObjArray* fFiles          List of file names containing the Trees
          TList* fStatus         List of active/inactive branches
        TObject* fNotify         Object to be notified when loading a new file

Class Description

                                                                      
 TChain                                                               
                                                                      
 A chain is a collection of files containg TTree objects.             
 When the chain is created, the first parameter is the default name   
 for the Tree to be processed later on.                               
                                                                      
 Enter a new element in the chain via the TChain::Add function.       
 Once a chain is defined, one can use the normal TTree functions      
 to Draw,Scan,etc.                                                    
                                                                      
 Use TChain::SetBranchStatus to activate one or more branches for all 
 the trees in the chain.                                              
                                                                      

*-*-*-*-*-*Default constructor for Chain*-*-*-*-*-*-*-*-*-*-*-*-*-*
*-*        ==============================

*-*-*-*-*-*-*-*-*-*-*-*-*Create a Chain*-*-*-*-*-*-*-*-*-*-*-*-*-*-*
*-*                      ==============

   A TChain is a collection of TFile objects.
    the first parameter "name" is the name of the TTree object
    in the files added with Add.
   Use TChain::Add to add a new element to this chain.

    Example:
  Suppose we have 3 files f1.root, f2.root and f3.root. Each file
  contains a TTree object named "T".
     TChain ch("T");  creates a chain to process a Tree called "T"
     ch.Add("f1.root");
     ch.Add("f2.root");
     ch.Add("f3.root");
     ch.Draw("x");
       The Draw function above will process the variable "x" in Tree "T"
       reading sequentially the 3 files in the chain ch.

*-*

*-*-*-*-*-*Default destructor for a Chain*-*-*-*-*-*-*-*-*-*-*-*
*-*        ==============================

       Add a new element to this chain.
       An element can be the name of another chain or the name of a file
       containing a tree.
    name may have the following format:
       //machine/file_name.root/subdir/tree_name
      machine, subdir and tree_name are optional. If tree_name is missing,
      the chain name will be assumed.

    if nentries < 0, the file is connected and the tree header read in memory
    to get the number of entries.
    if (nentries >= 0, the file is not connected, nentries is assumed to be
    the number of entries in the file. In this case, no check is made that
    the file exists and the Tree existing in the file. This second mode
    is interesting in case the number of entries in the file is already stored
    in a run data base for example.

*-*-*-*-*-*-*-*-*Initialize the packet descriptor string*-*-*-*-*-*-*-*-*-*
*-*              =======================================

 Draw expression varexp for selected entries.

 This function accepts TCut objects as arguments.
 Useful to use the string operator +, example:
    ntuple.Draw("x",cut1+cut2+cut3);

 Process all entries in this chain and draw histogram
 corresponding to expression varexp.

*-*-*-*-*-*-*-*-*Return pointer to the branch name*-*-*-*-*
*-*              ==========================================

*-*-*-*-*-*-*-*-*Return entry in memory*-*-*-*-*-*-*-*-*-*
*-*              ======================
     getall = 0 : get only active branches
     getall = 1 : get all branches

*-*-*-*-*-*-*-*-*Return pointer to the leaf name*-*-*-*-*
*-*              ==========================================

*-*-*-*-*-*-*-*-*Return pointer to list of branches of current tree*-*-*-*-*
*-*              ================================================

*-*-*-*-*-*-*-*-*Return pointer to list of leaves of current tree*-*-*-*-*
*-*              ================================================

*-*-*-*-*-*-*-*-*Return maximum of column with name columname*-*-*-*-*-*-*
*-*              ============================================

*-*-*-*-*-*-*-*-*Return minimum of column with name columname*-*-*-*-*-*-*
*-*              ============================================

*-*-*-*-*-*-*-*-*Return number of branches of current tree*-*-*-*-*
*-*              =========================================

    Load tree corresponding to entry

*-*-*-*-*-*-*-*-*Loop on nentries of this chain starting at firstentry
*-*              ===================================================

     Merge all files in this chain into a new file
 see important note in the following function Merge

     Merge all files in this chain into a new file
     if option ="C" is given, the compression level for all branches
        in the new Tree is set to the file compression level.
     By default, the compression level of all branches is the
     original compression level in the old Trees.

     if (basketsize > 1000, the basket size for all branches of the
     new Tree will be set to basketsize.

 IMPORTANT: Before invoking this function, the branch addresses
            of the TTree must have been set.
  example using the file generated in $ROOTSYS/test/Event
  merge two copies of Event.root

        gSystem.Load("libEvent");
        Event *event = new Event();
        TChain ch("T");
        ch.SetBranchAddress("event",&event);
        ch.Add("Event1.root");
        ch.Add("Event2.root");
        ch.Merge("all.root");

  The SetBranchAddress statement is not necessary if the Tree
  contains only basic types (case of files converted from hbook)

*-*-*-*-*-*-*-*-*Set branch address*-*-*-*-*-*-*-*
*-*              ==================

      bname is the name of a branch.
      add is the address of the branch.

*-*-*-*-*-*-*-*-*Set branch status Process or DoNotProcess*-*-*-*-*-*-*-*
*-*              =========================================

      bname is the name of a branch. if bname="*", apply to all branches.
      status = 1  branch will be processed
             = 0  branch will not be processed

*-*-*-*-*-*-*-*-*Set number of entries per packet for parallel root*-*-*-*-*
*-*              =================================================

*-*-*-*-*-*-*-*-*Stream a class object*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*
*-*              =========================================

Inline Functions

               void Draw(const char* varexp, const char* selection, Option_t* option, Int_t nentries = 1000000000, Int_t firstentry = 0)
              Int_t GetNtrees()
             TFile* GetFile()
         TObjArray* GetListOfFiles()
           TObject* GetNotify()
             TList* GetStatus()
             TTree* GetTree()
              Int_t GetTreeNumber()
             Int_t* GetTreeOffset()
              Int_t GetTreeOffsetLen()
               void SetNotify(TObject* obj)
            TClass* Class()
            TClass* IsA() const
               void ShowMembers(TMemberInspector& insp, char* parent)
             TChain TChain(TChain&)