TTreePlayer

class TTreePlayer : public TVirtualTreePlayer

    protected:

             void DeleteSelectorFromFile()
      const char* GetNameByIndex(TString& varexp, Int_t* index, Int_t colindex) const
             void TakeAction(Int_t nfill, Int_t& npoints, Int_t& action, TObject* obj, Option_t* option)
             void TakeEstimate(Int_t nfill, Int_t& npoints, Int_t action, TObject* obj, Option_t* option)

    public:

                             TTreePlayer()
                             TTreePlayer(const TTreePlayer&)
                     virtual ~TTreePlayer()
      virtual TVirtualIndex* BuildIndex(const TTree* T, const char* majorname, const char* minorname)
              static TClass* Class()
              virtual TTree* CopyTree(const char* selection, Option_t* option, Long64_t nentries, Long64_t firstentry)
            virtual Long64_t DrawScript(const char* wrapperPrefix, const char* macrofilename, const char* cutfilename, Option_t* option, Long64_t nentries, Long64_t firstentry)
            virtual Long64_t DrawSelect(const char* varexp, const char* selection, Option_t* option, Long64_t nentries, Long64_t firstentry)
            virtual Long64_t Fit(const char* formula, const char* varexp, const char* selection, Option_t* option, Option_t* goption, Long64_t nentries, Long64_t firstentry)
               virtual Int_t GetDimension() const
            virtual Long64_t GetEntriesToProcess(Long64_t firstentry, Long64_t nentries) const
                virtual TH1* GetHistogram() const
               virtual Int_t GetNfill() const
                 const char* GetScanFileName() const
       virtual TTreeFormula* GetSelect() const
            virtual Long64_t GetSelectedRows() const
                  TSelector* GetSelector() const
           virtual Double_t* GetV1() const
           virtual Double_t* GetV2() const
           virtual Double_t* GetV3() const
           virtual Double_t* GetV4() const
       virtual TTreeFormula* GetVar1() const
       virtual TTreeFormula* GetVar2() const
       virtual TTreeFormula* GetVar3() const
       virtual TTreeFormula* GetVar4() const
           virtual Double_t* GetW() const
             virtual TClass* IsA() const
               virtual Int_t MakeClass(const char* classname, Option_t* option)
               virtual Int_t MakeCode(const char* filename)
               virtual Int_t MakeProxy(const char* classname, const char* macrofilename = "0", const char* cutfilename = "0", const char* option = "0", Int_t maxUnrolling = 3)
         virtual TPrincipal* Principal(const char* varexp, const char* selection, Option_t* option, Long64_t nentries, Long64_t firstentry)
            virtual Long64_t Process(const char* filename, Option_t* option, Long64_t nentries, Long64_t firstentry)
            virtual Long64_t Process(TSelector* selector, Option_t* option, Long64_t nentries, Long64_t firstentry)
         virtual TSQLResult* Query(const char* varexp, const char* selection, Option_t* option, Long64_t nentries, Long64_t firstentry)
                virtual void RecursiveRemove(TObject* obj)
            virtual Long64_t Scan(const char* varexp, const char* selection, Option_t* option, Long64_t nentries, Long64_t firstentry)
                      Bool_t ScanRedirected()
                virtual void SetEstimate(Long64_t n)
                        void SetScanFileName(const char* name)
                        void SetScanRedirect(Bool_t on = kFALSE)
                virtual void SetTree(TTree* t)
                virtual void ShowMembers(TMemberInspector& insp, char* parent)
                virtual void StartViewer(Int_t ww, Int_t wh)
                virtual void Streamer(TBuffer& b)
                        void StreamerNVirtual(TBuffer& b)
            virtual Long64_t UnbinnedFit(const char* formula, const char* varexp, const char* selection, Option_t* option, Long64_t nentries, Long64_t firstentry)
                virtual void UpdateFormulaLeaves()

Data Members

    protected:

              TTree* fTree              !  Pointer to current Tree
              Bool_t fScanRedirect      Switch to redirect TTree::Scan output to a file
         const char* fScanFileName      Name of the file where Scan is redirected
               Int_t fDimension         Dimension of the current expression
            Long64_t fSelectedRows      Number of selected entries
                TH1* fHistogram         ! Pointer to histogram used for the projection
      TSelectorDraw* fSelector          ! Pointer to current selector
          TSelector* fSelectorFromFile  ! Pointer to a user defined selector created by this TTreePlayer object 
             TClass* fSelectorClass     ! Pointer to the actual class of the TSelectorFromFile
              TList* fInput             ! input list to the selector
              TList* fFormulaList       ! Pointer to a list of coordinated list TTreeFormula (used by Scan and Query)

Class Description

                                                                      
 TTree                                                                
                                                                      
  a TTree object has a header with a name and a title.
  It consists of a list of independent branches (TBranch). Each branch
  has its own definition and list of buffers. Branch buffers may be
  automatically written to disk or kept in memory until the Tree attribute
  fMaxVirtualSize is reached.
  Variables of one branch are written to the same buffer.
  A branch buffer is automatically compressed if the file compression
  attribute is set (default).

  Branches may be written to different files (see TBranch::SetFile).

  The ROOT user can decide to make one single branch and serialize one
  object into one single I/O buffer or to make several branches.
  Making one single branch and one single buffer can be the right choice
  when one wants to process only a subset of all entries in the tree.
  (you know for example the list of entry numbers you want to process).
  Making several branches is particularly interesting in the data analysis
  phase, when one wants to histogram some attributes of an object (entry)
  without reading all the attributes.

  ==> TTree *tree = new TTree(name, title, maxvirtualsize)
     Creates a Tree with name and title. Maxvirtualsize is by default 64Mbytes,
     maxvirtualsize = 64000000(default) means: Keeps as many buffers in memory until
     the sum of all buffers is greater than 64 Megabyte. When this happens,
     memory buffers are written to disk and deleted until the size of all
     buffers is again below the threshold.
     maxvirtualsize = 0 means: keep only one buffer in memory.

     Various kinds of branches can be added to a tree:
       A - simple structures or list of variables. (may be for C or Fortran structures)
       B - any object (inheriting from TObject). (we expect this option be the most frequent)
       C - a ClonesArray. (a specialized object for collections of same class objects)

  ==> Case A
      ======
     TBranch *branch = tree->Branch(branchname,address, leaflist, bufsize)
       * address is the address of the first item of a structure
       * leaflist is the concatenation of all the variable names and types
         separated by a colon character :
         The variable name and the variable type are separated by a slash (/).
         The variable type may be 0,1 or 2 characters. If no type is given,
         the type of the variable is assumed to be the same as the previous
         variable. If the first variable does not have a type, it is assumed
         of type F by default. The list of currently supported types is given below:
            - C : a character string terminated by the 0 character
            - B : an 8 bit signed integer (Char_t)
            - b : an 8 bit unsigned integer (UChar_t)
            - S : a 16 bit signed integer (Short_t)
            - s : a 16 bit unsigned integer (UShort_t)
            - I : a 32 bit signed integer (Int_t)
            - i : a 32 bit unsigned integer (UInt_t)
            - F : a 32 bit floating point (Float_t)
            - D : a 64 bit floating point (Double_t)

  ==> Case B
      ======
     TBranch *branch = tree->Branch(branchname,className,object, bufsize, splitlevel)
          object is the address of a pointer to an existing object (derived from TObject).
        if splitlevel=1 (default), this branch will automatically be split
          into subbranches, with one subbranch for each data member or object
          of the object itself. In case the object member is a TClonesArray,
          the mechanism described in case C is applied to this array.
        if splitlevel=0, the object is serialized in the branch buffer.

  ==> Case C
      ======
     TBranch *branch = tree->Branch(branchname,clonesarray, bufsize, splitlevel)
         clonesarray is the address of a pointer to a TClonesArray.
         The TClonesArray is a direct access list of objects of the same class.
         For example, if the TClonesArray is an array of TTrack objects,
         this function will create one subbranch for each data member of
         the object TTrack.


  ==> branch->SetAddress(Void *address)
      In case of dynamic structures changing with each entry for example, one must
      redefine the branch address before filling the branch again.
      This is done via the TBranch::SetAddress member function.

  ==> tree->Fill()
      loops on all defined branches and for each branch invokes the Fill function.

         See also the class TNtuple (a simple Tree with only one branch)

  =============================================================================
______________________________________________________________________________
*-*-*-*-*-*-*A simple example with histograms and a tree*-*-*-*-*-*-*-*-*-*
*-*          ===========================================

  This program creates :
    - a one dimensional histogram
    - a two dimensional histogram
    - a profile histogram
    - a tree

  These objects are filled with some random numbers and saved on a file.

-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*

 #include "TFile.h"
 #include "TH1.h"
 #include "TH2.h"
 #include "TProfile.h"
 #include "TRandom.h"
 #include "TTree.h"


 //______________________________________________________________________________
 main(int argc, char **argv)
 {
 // Create a new ROOT binary machine independent file.
 // Note that this file may contain any kind of ROOT objects, histograms,trees
 // pictures, graphics objects, detector geometries, tracks, events, etc..
 // This file is now becoming the current directory.
   TFile hfile("htree.root","RECREATE","Demo ROOT file with histograms & trees");

 // Create some histograms and a profile histogram
   TH1F *hpx   = new TH1F("hpx","This is the px distribution",100,-4,4);
   TH2F *hpxpy = new TH2F("hpxpy","py ps px",40,-4,4,40,-4,4);
   TProfile *hprof = new TProfile("hprof","Profile of pz versus px",100,-4,4,0,20);

 // Define some simple structures
   typedef struct {Float_t x,y,z;} POINT;
   typedef struct {
      Int_t ntrack,nseg,nvertex;
      UInt_t flag;
      Float_t temperature;
   } EVENTN;
   static POINT point;
   static EVENTN eventn;

 // Create a ROOT Tree
   TTree *tree = new TTree("T","An example of ROOT tree with a few branches");
   tree->Branch("point",&point,"x:y:z");
   tree->Branch("eventn",&eventn,"ntrack/I:nseg:nvertex:flag/i:temperature/F");
   tree->Branch("hpx","TH1F",&hpx,128000,0);

   Float_t px,py,pz;
   static Float_t p[3];

 //--------------------Here we start a loop on 1000 events
   for ( Int_t i=0; i<1000; i++) {
      gRandom->Rannor(px,py);
      pz = px*px + py*py;
      Float_t random = gRandom->::Rndm(1);

 //         Fill histograms
      hpx->Fill(px);
      hpxpy->Fill(px,py,1);
      hprof->Fill(px,pz,1);

 //         Fill structures
      p[0] = px;
      p[1] = py;
      p[2] = pz;
      point.x = 10*(random-1);;
      point.y = 5*random;
      point.z = 20*random;
      eventn.ntrack  = Int_t(100*random);
      eventn.nseg    = Int_t(2*eventn.ntrack);
      eventn.nvertex = 1;
      eventn.flag    = Int_t(random+0.5);
      eventn.temperature = 20+random;

 //        Fill the tree. For each event, save the 2 structures and 3 objects
 //      In this simple example, the objects hpx, hprof and hpxpy are slightly
 //      different from event to event. We expect a big compression factor!
      tree->Fill();
   }
  //--------------End of the loop

   tree->Print();

 // Save all objects in this file
   hfile.Write();

 // Close the file. Note that this is automatically done when you leave
 // the application.
   hfile.Close();

   return 0;
 }
                                                                      

*-*-*-*-*-*-*-*-*-*-*Default Tree constructor*-*-*-*-*-*-*-*-*-*-*-*-*-*
*-*                  ========================

*-*-*-*-*-*-*-*-*-*-*Tree destructor*-*-*-*-*-*-*-*-*-*-*-*-*-*-*
*-*                  =================

 copy a Tree with selection
 make a clone of this Tree header.
 then copy the selected entries

 selection is a standard selection expression (see TTreePlayer::Draw)
 option is reserved for possible future use
 nentries is the number of entries to process (default is all)
 first is the first entry to process (default is 0)

 IMPORTANT: The copied tree stays connected with this tree until this tree
            is deleted.  In particular, any changes in branch addresses
            in this tree are forwarded to the clone trees.  Any changes
            made to the branch addresses of the copied trees are over-ridden
            anytime this tree changes its branch addresses.
            Once this tree is deleted, all the addresses of the copied tree
            are reset to their default values.

 The following example illustrates how to copy some events from the Tree
 generated in $ROOTSYS/test/Event

   gSystem->Load("libEvent");
   TFile f("Event.root");
   TTree *T = (TTree*)f.Get("T");
   Event *event = new Event();
   T->SetBranchAddress("event",&event);
   TFile f2("Event2.root","recreate");
   TTree *T2 = T->CopyTree("fNtrack<595");
   T2->Write();

 Delete any selector created by this object.
 The selector has been created using TSelector::GetSelector(file)

 Draw the result of a C++ script

 macrofilename and optionally cutfilename are assumed to contain
 at least a method with the same name as the file.  The method
 should return a value that can be automatically cast to
 respectively a double and a boolean.

 Both methods will be executed in a context such that the
 branch names can be used as C++ variables. This is
 accomplished by generating a TTreeProxy (see MakeProxy)
 and including the files in the proper location.

 If the branch name can not be used a proper C++ symbol name,
 it will be modified as follow:
    - white spaces are removed
    - if the leadind character is not a letter, an underscore is inserted
    - < and > are replace by underscores
    - * is replaced by st
    - & is replaced by rf

 If a cutfilename is specified, for each entry, we execute
   if (cutfilename()) htemp->Fill(macrofilename());
 If no cutfilename is specified, for each entry we execute
   htemp(macrofilename());

 The default for the histogram are the same as for
 TTreePlayer::DrawSelect

*-*-*-*-*-*-*-*-*-*-*Draw expression varexp for specified entries-*-*-*-*-*
*-*                  ============================================

  varexp is an expression of the general form
   - "e1"           produces a 1-d histogram of expression "e1"
   - "e1:e2"        produces a 2-d histogram (or profile) of "e1" versus "e2"
   - "e1:e2:e3"     produces a 3-d scatter-plot of "e1" versus "e2" versus "e3"
   - "e1:e2:e3:e4"  produces a 3-d scatter-plot of "e1" versus "e2" versus "e3"
                    and "e4" mapped on the color number.

  Example:
     varexp = x     simplest case: draw a 1-Dim distribution of column named x
            = sqrt(x)            : draw distribution of sqrt(x)
            = x*y/z
            = y:sqrt(x) 2-Dim distribution of y versus sqrt(x)
            = px:py:pz:2.5*E  produces a 3-d scatter-plot of px vs py ps pz
              and the color number of each marker will be 2.5*E.
              If the color number is negative it is set to 0.
              If the color number is greater than the current number of colors
                 it is set to the highest color number.
              The default number of colors is 50.
              see TStyle::SetPalette for setting a new color palette.

  Note that the variables e1, e2 or e3 may contain a selection.
  example, if e1= x*(y<0), the value histogrammed will be x if y<0
  and will be 0 otherwise.

  selection is an expression with a combination of the columns.
  In a selection all the C++ operators are authorized.
  The value corresponding to the selection expression is used as a weight
  to fill the histogram.
  If the expression includes only boolean operations, the result
  is 0 or 1. If the result is 0, the histogram is not filled.
  In general, the expression may be of the form:
      value*(boolean expression)
  if boolean expression is true, the histogram is filled with
  a weight = value.
  Examples:
      selection1 = "x<y && sqrt(z)>3.2"
      selection2 = "(x+y)*(sqrt(z)>3.2"
  selection1 returns a weigth = 0 or 1
  selection2 returns a weight = x+y if sqrt(z)>3.2
             returns a weight = 0 otherwise.

  option is the drawing option
      see TH1::Draw for the list of all drawing options.
      If option contains the string "goff", no graphics is generated.

  nentries is the number of entries to process (default is all)
  first is the first entry to process (default is 0)

     Drawing expressions using arrays and array elements
     ===================================================
 Let assumes, a leaf fMatrix, on the branch fEvent, which is a 3 by 3 array,
 or a TClonesArray.
 In a TTree::Draw expression you can now access fMatrix using the following
 syntaxes:

   String passed    What is used for each entry of the tree

   "fMatrix"       the 9 elements of fMatrix
   "fMatrix[][]"   the 9 elements of fMatrix
   "fMatrix[2][2]" only the elements fMatrix[2][2]
   "fMatrix[1]"    the 3 elements fMatrix[1][0], fMatrix[1][1] and fMatrix[1][2]
   "fMatrix[1][]"  the 3 elements fMatrix[1][0], fMatrix[1][1] and fMatrix[1][2]
   "fMatrix[][0]"  the 3 elements fMatrix[0][0], fMatrix[1][0] and fMatrix[2][0]

   "fEvent.fMatrix...." same as "fMatrix..." (unless there is more than one leaf named fMatrix!).

 In summary, if a specific index is not specified for a dimension, TTree::Draw
 will loop through all the indices along this dimension.  Leaving off the
 last (right most) dimension of specifying then with the two characters '[]'
 is equivalent.  For variable size arrays (and TClonesArray) the range
 of the first dimension is recalculated for each entry of the tree.
 You can also specify the index as an expression of any other variables from the
 tree.

 TTree::Draw also now properly handling operations involving 2 or more arrays.

 Let assume a second matrix fResults[5][2], here are a sample of some
 of the possible combinations, the number of elements they produce and
 the loop used:

  expression                       element(s)  Loop

  "fMatrix[2][1] - fResults[5][2]"   one     no loop
  "fMatrix[2][]  - fResults[5][2]"   three   on 2nd dim fMatrix
  "fMatrix[2][]  - fResults[5][]"    two     on both 2nd dimensions
  "fMatrix[][2]  - fResults[][1]"    three   on both 1st dimensions
  "fMatrix[][2]  - fResults[][]"     six     on both 1st and 2nd dimensions of
                                             fResults
  "fMatrix[][2]  - fResults[3][]"    two     on 1st dim of fMatrix and 2nd of
                                             fResults (at the same time)
  "fMatrix[][]   - fResults[][]"     six     on 1st dim then on  2nd dim

  "fMatrix[][fResult[][]]"           30      on 1st dim of fMatrix then on both
                                             dimensions of fResults.  The value
                                             if fResults[j][k] is used as the second
                                             index of fMatrix.

 In summary, TTree::Draw loops through all un-specified dimensions.  To
 figure out the range of each loop, we match each unspecified dimension
 from left to right (ignoring ALL dimensions for which an index has been
 specified), in the equivalent loop matched dimensions use the same index
 and are restricted to the smallest range (of only the matched dimensions).
 When involving variable arrays, the range can of course be different
 for each entry of the tree.

 So the loop equivalent to "fMatrix[][2] - fResults[3][]" is:

    for (Int_t i0; i0 < min(3,2); i0++) {
       use the value of (fMatrix[i0][2] - fMatrix[3][i0])
    }

 So the loop equivalent to "fMatrix[][2] - fResults[][]" is:

    for (Int_t i0; i0 < min(3,5); i0++) {
       for (Int_t i1; i1 < 2; i1++) {
          use the value of (fMatrix[i0][2] - fMatrix[i0][i1])
       }
    }

 So the loop equivalent to "fMatrix[][] - fResults[][]" is:

    for (Int_t i0; i0 < min(3,5); i0++) {
       for (Int_t i1; i1 < min(3,2); i1++) {
          use the value of (fMatrix[i0][i1] - fResults[i0][i1])
       }
    }

 So the loop equivalent to "fMatrix[][fResults[][]]" is:

    for (Int_t i0; i0 < 3; i0++) {
       for (Int_t j2; j2 < 5; j2++) {
          for (Int_t j3; j3 < 2; j3++) {
             i1 = fResults[j2][j3];
             use the value of fMatrix[i0][i1]
       }
    }

     Saving the result of Draw to an histogram
     =========================================
  By default the temporary histogram created is called htemp.
  One can retrieve a pointer to this histogram with:
    TH1F *htemp = (TH1F*)gPad->GetPrimitive("htemp");

  If varexp0 contains >>hnew (following the variable(s) name(s),
  the new histogram created is called hnew and it is kept in the current
  directory (and also the current pad).
  Example:
    tree.Draw("sqrt(x)>>hsqrt","y>0")
    will draw sqrt(x) and save the histogram as "hsqrt" in the current
    directory.  To retrieve it do:
    TH1F *hsqrt = (TH1F*)gDirectory->Get("hsqrt");

  The binning information is taken from the environment variables

     Hist.Binning.?D.?

  In addition, the name of the histogram can be followed by up to 9
  numbers between '(' and ')', where the numbers describe the
  following:

   1 - bins in x-direction
   2 - lower limit in x-direction
   3 - upper limit in x-direction
   4-6 same for y-direction
   7-9 same for z-direction

   When a new binning is used the new value will become the default.
   Values can be skipped.
  Example:
    tree.Draw("sqrt(x)>>hsqrt(500,10,20)"
          // plot sqrt(x) between 10 and 20 using 500 bins
    tree.Draw("sqrt(x):sin(y)>>hsqrt(100,10,60,50,.1,.5)"
          // plot sqrt(x) against sin(y)
          // 100 bins in x-direction; lower limit on x-axis is 10; upper limit is 60
          //  50 bins in y-direction; lower limit on y-axis is .1; upper limit is .5

  By default, the specified histogram is reset.
  To continue to append data to an existing histogram, use "+" in front
  of the histogram name.
  A '+' in front of the histogram name is ignored, when the name is followed by
  binning information as described in the previous paragraph.
    tree.Draw("sqrt(x)>>+hsqrt","y>0")
      will not reset hsqrt, but will continue filling.
  This works for 1-D, 2-D and 3-D histograms.

     Accessing collection objects
     ============================

  TTree::Draw default's handling of collections is to assume that any
  request on a collection pertain to it content.  For example, if fTracks
  is a collection of Track objects, the following:
      tree->Draw("event.fTracks.fPx");
  will plot the value of fPx for each Track objects inside the collection.
  Also
     tree->Draw("event.fTracks.size()");
  would plot the result of the member function Track::size() for each
  Track object inside the collection.
  To access information about the collection itself, TTree::Draw support
  the '@' notation.  If a variable which points to a collection is prefixed
  or postfixed with '@', the next part of the expression will pertain to
  the collection object.  For example:
     tree->Draw("event.@fTracks.size()");
  will plot the size of the collection refered to by fTracks (i.e the number
  of Track objects).

     Special functions and variables
     ===============================

  Entry$:  A TTree::Draw formula can use the special variable Entry$
  to access the entry number being read.  For example to draw every
  other entry use:
    tree.Draw("myvar","Entry$%2==0");

  Entry$    : return the current entry number (== TTree::GetReadEntry())
  Entries$  : return the total number of entries (== TTree::GetEntries())
  Length$   : return the total number of element of this formula for this
              entry (==TTreeFormula::GetNdata())
  Iteration$: return the current iteration over this formula for this
                 entry (i.e. varies from 0 to Length$).

  Length$(formula): return the total number of element of the formula given as a
                    parameter.
  Sum$(formula): return the sum of the value of the elements of the formula given
                    as a parameter.  For eaxmple the mean for all the elements in
                    one entry can be calculated with:
                Sum$(formula)/Length$(formula)

  Alt$(primary,alternate) : return the value of "primary" if it is available
                 for the current iteration otherwise return the value of "alternate".
                 For example, with arr1[3] and arr2[2]
    tree->Draw("arr1+Alt$(arr2,0)");
                 will draw arr[0]+arr2[0] ; arr[1]+arr2[1] and arr[1]+0
                 Or with a variable size array arr3
    tree->Draw("Alt$(arr3[0],0)+Alt$(arr3[1],0)+Alt$(arr3[2],0)");
                 will draw the sum arr3 for the index 0 to min(2,actual_size_of_arr3-1)
                 As a comparison
    tree->Draw("arr3[0]+arr3[1]+arr3[2]");
                 will draw the sum arr3 for the index 0 to 2 only if the
                 actual_size_of_arr3 is greater or equal to 3.
                 Note that the array in 'primary' is flatened/linearilized thus using
                 Alt$ with multi-dimensional arrays of different dimensions in unlikely
                 to yield the expected results.  To visualize a bit more what elements
                 would be matched by TTree::Draw, TTree::Scan can be used:
    tree->Scan("arr1:Alt$(arr2,0)");
                 will print on one line the value of arr1 and (arr2,0) that will be
                 matched by
    tree->Draw("arr1-Alt$(arr2,0)");

     Drawing a user function accessing the TTree data directly
     =========================================================

  If the formula contains  a file name, TTree::MakeProxy will be used
  to load and execute this file.   In particular it will draw the
  result of a function with the same name as the file.  The function
  will be executed in a context where the name of the branches can
  be used as a C++ variable.

  For example draw px using the file hsimple.root (generated by the
  hsimple.C tutorial), we need a file named hsimple.cxx:

     double hsimple() {
        return px;
     }

  MakeProxy can then be used indirectly via the TTree::Draw interface
  as follow:
     new TFile("hsimple.root")
     ntuple->Draw("hsimple.cxx");

  A more complete example is available in the tutorials directory:
    h1analysisProxy.cxx , h1analysProxy.h and h1analysisProxyCut.C
  which reimplement the selector found in h1analysis.C

  The main features of this facility are:

    * on-demand loading of branches
    * ability to use the 'branchname' as if it was a data member
    * protection against array out-of-bound
    * ability to use the branch data as object (when the user code is available)

  See TTree::MakeProxy for more details.

     Making a Profile histogram
     ==========================
  In case of a 2-Dim expression, one can generate a TProfile histogram
  instead of a TH2F histogram by specyfying option=prof or option=profs.
  The option=prof is automatically selected in case of y:x>>pf
  where pf is an existing TProfile histogram.

     Making a 2D Profile histogram
     ==========================
  In case of a 3-Dim expression, one can generate a TProfile2D histogram
  instead of a TH3F histogram by specyfying option=prof or option=profs.
  The option=prof is automatically selected in case of z:y:x>>pf
  where pf is an existing TProfile2D histogram.

     Saving the result of Draw to a TEventList
     =========================================
  TTree::Draw can be used to fill a TEventList object (list of entry numbers)
  instead of histogramming one variable.
  If varexp0 has the form >>elist , a TEventList object named "elist"
  is created in the current directory. elist will contain the list
  of entry numbers satisfying the current selection.
  Example:
    tree.Draw(">>yplus","y>0")
    will create a TEventList object named "yplus" in the current directory.
    In an interactive session, one can type (after TTree::Draw)
       yplus.Print("all")
    to print the list of entry numbers in the list.

  By default, the specified entry list is reset.
  To continue to append data to an existing list, use "+" in front
  of the list name;
    tree.Draw(">>+yplus","y>0")
      will not reset yplus, but will enter the selected entries at the end
      of the existing list.

      Using a TEventList as Input
      ===========================
  Once a TEventList object has been generated, it can be used as input
  for TTree::Draw. Use TTree::SetEventList to set the current event list
  Example:
     TEventList *elist = (TEventList*)gDirectory->Get("yplus");
     tree->SetEventList(elist);
     tree->Draw("py");

  If arrays are used in the selection critera, the event entered in the
  list are all the event that have at least one element of the array that
  satisfy the selection.
  Example:
      tree.Draw(">>pyplus","fTracks.fPy>0");
      tree->SetEventList(pyplus);
      tree->Draw("fTracks.fPy");
  will draw the fPy of ALL tracks in event with at least one track with
  a positive fPy.

  To select only the elements that did match the original selection
  use TEventList::SetReapplyCut.
  Example:
      tree.Draw(">>pyplus","fTracks.fPy>0");
      pyplus->SetReapplyCut(kTRUE);
      tree->SetEventList(pyplus);
      tree->Draw("fTracks.fPy");
  will draw the fPy of only the tracks that have a positive fPy.

  Note: Use tree->SetEventList(0) if you do not want use the list as input.

      How to obtain more info from TTree::Draw
      ========================================

  Once TTree::Draw has been called, it is possible to access useful
  information still stored in the TTree object via the following functions:
    -GetSelectedRows()    // return the number of entries accepted by the
                          //selection expression. In case where no selection
                          //was specified, returns the number of entries processed.
    -GetV1()              //returns a pointer to the float array of V1
    -GetV2()              //returns a pointer to the float array of V2
    -GetV3()              //returns a pointer to the float array of V3
    -GetW()               //returns a pointer to the double array of Weights
                          //where weight equal the result of the selection expression.
   where V1,V2,V3 correspond to the expressions in
   TTree::Draw("V1:V2:V3",selection);

   Example:
    Root > ntuple->Draw("py:px","pz>4");
    Root > TGraph *gr = new TGraph(ntuple->GetSelectedRows(),
                                   ntuple->GetV2(), ntuple->GetV1());
    Root > gr->Draw("ap"); //draw graph in current pad
    creates a TGraph object with a number of points corresponding to the
    number of entries selected by the expression "pz>4", the x points of the graph
    being the px values of the Tree and the y points the py values.

   Important note: By default TTree::Draw creates the arrays obtained
    with GetV1, GetV2, GetV3, GetW with a length corresponding to the
    parameter fEstimate. By default fEstimate=10000 and can be modified
    via TTree::SetEstimate. A possible recipee is to do
       tree->SetEstimate(tree->GetEntries());
    You must call SetEstimate if the expected number of selected rows
    is greater than 10000.

    You can use the option "goff" to turn off the graphics output
    of TTree::Draw in the above example.

           Automatic interface to TTree::Draw via the TTreeViewer
           ======================================================

    A complete graphical interface to this function is implemented
    in the class TTreeViewer.
    To start the TTreeViewer, three possibilities:
       - select TTree context menu item "StartViewer"
       - type the command  "TTreeViewer TV(treeName)"
       - execute statement "tree->StartViewer();"

*-*-*-*-*-*-*-*-*Fit  a projected item(s) from a Tree*-*-*-*-*-*-*-*-*-*
*-*              ======================================

  formula is a TF1 expression.

  See TTree::Draw for explanations of the other parameters.

  By default the temporary histogram created is called htemp.
  If varexp contains >>hnew , the new histogram created is called hnew
  and it is kept in the current directory.
  Example:
    tree.Fit("pol4","sqrt(x)>>hsqrt","y>0")
    will fit sqrt(x) and save the histogram as "hsqrt" in the current
    directory.

 return the number of entries to be processed
 this function checks that nentries is not bigger than the number
 of entries in the Tree or in the associated TEventlist

*-*-*-*-*-*-*-*-*Return name corresponding to colindex in varexp*-*-*-*-*-*
*-*              ===============================================

   varexp is a string of names separated by :
   index is an array with pointers to the start of name[i] in varexp

 Generate skeleton analysis class for this Tree

 The following files are produced: classname.h and classname.C
 If classname is 0, classname will be called "nameoftree.

 The generated code in classname.h includes the following:
    - Identification of the original Tree and Input file name
    - Definition of analysis class (data and functions)
    - the following class functions:
       - constructor (connecting by default the Tree file)
       - GetEntry(Long64_t entry)
       - Init(TTree *tree) to initialize a new TTree
       - Show(Long64_t entry) to read and Dump entry

 The generated code in classname.C includes only the main
 analysis function Loop.

 To use this function:
    - connect your Tree file (eg: TFile f("myfile.root");)
    - T->MakeClass("MyClass");
 where T is the name of the Tree in file myfile.root
 and MyClass.h, MyClass.C the name of the files created by this function.
 In a ROOT session, you can do:
    root > .L MyClass.C
    root > MyClass t
    root > t.GetEntry(12); // Fill t data members with entry number 12
    root > t.Show();       // Show values of entry 12
    root > t.Show(16);     // Read and show values of entry 16
    root > t.Loop();       // Loop on all entries

 Generate skeleton function for this Tree

 The function code is written on filename.
 If filename is 0, filename will be called nameoftree.C

 The generated code includes the following:
    - Identification of the original Tree and Input file name
    - Connection of the Tree file
    - Declaration of Tree variables
    - Setting of branches addresses
    - A skeleton for the entry loop

 To use this function:
    - connect your Tree file (eg: TFile f("myfile.root");)
    - T->MakeCode("anal.C");
 where T is the name of the Tree in file myfile.root
 and anal.C the name of the file created by this function.

 NOTE: Since the implementation of this function, a new and better
       function TTree::MakeClass() has been developped.

 Generate a skeleton analysis class for this Tree using TBranchProxy.
 TBranchProxy is the base of a class hierarchy implementing an
 indirect access to the content of the branches of a TTree.

 "proxyClassname" is expected to be of the form:
    [path/]fileprefix
 The skeleton will then be generated in the file:
    fileprefix.h
 located in the current directory or in 'path/' if it is specified.
 The class generated will be named 'fileprefix'

 "macrofilename" and optionally "cutfilename" are expected to point
 to source file which will be included in by the generated skeletong.
 Method of the same name as the file(minus the extension and path)
 will be called by the generated skeleton's Process method as follow:
    [if (cutfilename())] htemp->Fill(macrofilename());

 "option" can be used select some of the optional features during
 the code generation.  The possible options are:
    nohist : indicates that the generated ProcessFill should not
             fill the histogram.

 'maxUnrolling' controls how deep in the class hierachy does the
 system 'unroll' class that are not split.  'unrolling' a class
 will allow direct access to its data members a class (this
 emulates the behavior of TTreeFormula).

 The main features of this skeleton are:

    * on-demand loading of branches
    * ability to use the 'branchname' as if it was a data member
    * protection against array out-of-bound
    * ability to use the branch data as object (when the user code is available)

 For example with Event.root, if
    Double_t somepx = fTracks.fPx[2];
 is executed by one of the method of the skeleton,
 somepx will updated with the current value of fPx of the 3rd track.

 Both macrofilename and the optional cutfilename are expected to be
 the name of source files which contain at least a free standing
 function with the signature:
     x_t macrofilename(); // i.e function with the same name as the file
 and
     y_t cutfilename();   // i.e function with the same name as the file

 x_t and y_t needs to be types that can convert respectively to a double
 and a bool (because the skeleton uses:
     if (cutfilename()) htemp->Fill(macrofilename());

 This 2 functions are run in a context such that the branch names are
 available as local variables of the correct (read-only) type.

 Note that if you use the same 'variable' twice, it is more efficient
 to 'cache' the value. For example
   Int_t n = fEventNumber; // Read fEventNumber
   if (n<10 || n>10) { ... }
 is more efficient than
   if (fEventNumber<10 || fEventNumber>10)

 Also, optionally, the generated selector will also call methods named
 macrofilename_methodname in each of 6 main selector methods if the method
 macrofilename_methodname exist (Where macrofilename is stripped of its
 extension).

 Concretely, with the script named h1analysisProxy.C,

 The method         calls the method (if it exist)
 Begin           -> h1analysisProxy_Begin
 SlaveBegin      -> h1analysisProxy_SlaveBegin
 Notify          -> h1analysisProxy_Notify
 Process         -> h1analysisProxy_Process
 SlaveTerminate  -> h1analysisProxy_SlaveTerminate
 Terminate       -> h1analysisProxy_Terminate

 If a file name macrofilename.h (or .hh, .hpp, .hxx, .hPP, .hXX) exist
 it is included before the declaration of the proxy class.  This can
 be used in particular to insure that the include files needed by
 the macro file are properly loaded.

 The default histogram is accessible via the variable named 'htemp'.

 If the library of the classes describing the data in the branch is
 loaded, the skeleton will add the needed #include statements and
 give the ability to access the object stored in the branches.

 To draw px using the file hsimple.root (generated by the
 hsimple.C tutorial), we need a file named hsimple.cxx:

     double hsimple() {
        return px;
     }

 MakeProxy can then be used indirectly via the TTree::Draw interface
 as follow:
     new TFile("hsimple.root")
     ntuple->Draw("hsimple.cxx");

 A more complete example is available in the tutorials directory:
   h1analysisProxy.cxx , h1analysProxy.h and h1analysisProxyCut.C
 which reimplement the selector found in h1analysis.C

*-*-*-*-*-*-*-*-*Interface to the Principal Components Analysis class*-*-*
*-*              ====================================================

   Create an instance of TPrincipal
   Fill it with the selected variables
   if option "n" is specified, the TPrincipal object is filled with
                 normalized variables.
   If option "p" is specified, compute the principal components
   If option "p" and "d" print results of analysis
   If option "p" and "h" generate standard histograms
   If option "p" and "c" generate code of conversion functions
   return a pointer to the TPrincipal object. It is the user responsability
   to delete this object.
   The option default value is "np"

   see TTreePlayer::DrawSelect for explanation of the other parameters.

*-*-*-*-*-*-*-*-*Process this tree executing the code in filename*-*-*-*-*
*-*              ================================================

   The code in filename is loaded (interpreted or compiled , see below)
   filename must contain a valid class implementation derived from TSelector.
   where TSelector has the following member functions:

     void TSelector::Begin(). This function is called before looping on the
          events in the Tree. The user can create his histograms in this function.

     Bool_t TSelector::Notify(). This function is called at the first entry
          of a new file in a chain.

     Bool_t TSelector::ProcessCut(Long64_t tentry). This function is called
          before processing tentry. It is the user's responsability to read
          the corresponding entry in memory (may be just a partial read).
          The function returns kTRUE if the entry must be processed,
          kFALSE otherwise. tentry is the entry number in the current Tree.

     void TSelector::ProcessFill(Long64_t tentry). This function is called for
          all selected events. User fills histograms in this function.

     void TSelector::Terminate(). This function is called at the end of
          the loop on all events.

   if filename is of the form file.C, the file will be interpreted.
   if filename is of the form file.C++, the file file.C will be compiled
      and dynamically loaded.
   if filename is of the form file.C+, the file file.C will be compiled
      and dynamically loaded. At next call, if file.C is older than file.o
      and file.so, the file.C is not compiled, only file.so is loaded.

  NOTE1
  It may be more interesting to invoke directly the other Process function
  accepting a TSelector* as argument.eg
     MySelector *selector = (MySelector*)TSelector::GetSelector(filename);
     selector->CallSomeFunction(..);
     mytree.Process(selector,..);

  NOTE2
  One should not call this function twice with the same selector file
  in the same script. If this is required, proceed as indicated in NOTE1,
  by getting a pointer to the corresponding TSelector,eg
    workaround 1
    ------------
void stubs1() {
   TSelector *selector = TSelector::GetSelector("h1test.C");
   TFile *f1 = new TFile("stubs_nood_le1.root");
   TTree *h1 = (TTree*)f1->Get("h1");
   h1->Process(selector);
   TFile *f2 = new TFile("stubs_nood_le1_coarse.root");
   TTree *h2 = (TTree*)f2->Get("h1");
   h2->Process(selector);
}
  or use ACLIC to compile the selector
   workaround 2
   ------------
void stubs2() {
   TFile *f1 = new TFile("stubs_nood_le1.root");
   TTree *h1 = (TTree*)f1->Get("h1");
   h1->Process("h1test.C+");
   TFile *f2 = new TFile("stubs_nood_le1_coarse.root");
   TTree *h2 = (TTree*)f2->Get("h1");
   h2->Process("h1test.C+");
}

*-*-*-*-*-*-*-*-*Process this tree executing the code in selector*-*-*-*-*
*-*              ================================================

   The TSelector class has the following member functions:

     void TSelector::Begin(). This function is called before looping on the
          events in the Tree. The user can create his histograms in this function.

     Bool_t TSelector::Notify(). This function is called at the first entry
          of a new file in a chain.

     Bool_t TSelector::ProcessCut(Long64_t tentry). This function is called
          before processing tentry. It is the user's responsability to read
          the corresponding entry in memory (may be just a partial read).
          The function returns kTRUE if the entry must be processed,
          kFALSE otherwise. tentry is the entry number in the current Tree.

     void TSelector::ProcessFill(Long64_t tentry). This function is called for
          all selected events. User fills histograms in this function.

     void TSelector::Terminate(). This function is called at the end of
          the loop on all events.

  If the Tree (Chain) has an associated EventList, the loop is on the nentries
  of the EventList, starting at firstentry, otherwise the loop is on the
  specified Tree entries.

 cleanup pointers in the player pointing to obj

 Loop on Tree and print entries passing selection. If varexp is 0 (or "")
 then print only first 8 columns. If varexp = "*" print all columns.
 Otherwise a columns selection can be made using "var1:var2:var3".
 The function returns the number of entries passing the selection.

 By default 50 rows are shown and you are asked for <CR>
 to see the next 50 rows.
 You can change the default number of rows to be shown before <CR>
 via  mytree->SetScanfield(maxrows) where maxrows is 50 by default.
 if maxrows is set to 0 all rows of the Tree are shown.
 This option is interesting when dumping the contents of a Tree to
 an ascii file, eg from the command line
   tree->SetScanField(0);
   tree->Scan("*"); >tree.log
  will create a file tree.log

 Arrays (within an entry) are printed in their linear forms.
 If several arrays with multiple dimensions are printed together,
 they will NOT be synchronized.  For example print
   arr1[4][2] and arr2[2][3] will results in a printing similar to:
 ***********************************************
 *    Row   * Instance *      arr1 *      arr2 *
 ***********************************************
 *        x *        0 * arr1[0][0]* arr2[0][0]*
 *        x *        1 * arr1[0][1]* arr2[0][1]*
 *        x *        2 * arr1[1][0]* arr2[0][2]*
 *        x *        3 * arr1[1][1]* arr2[1][0]*
 *        x *        4 * arr1[2][0]* arr2[1][1]*
 *        x *        5 * arr1[2][1]* arr2[1][2]*
 *        x *        6 * arr1[3][0]*           *
 *        x *        7 * arr1[3][1]*           *

 However, if there is a selection criterium which is an array, then
 all the formulas will be synchronized with the selection criterium
 (see TTreePlayer::DrawSelect for more information).

 The options string can contains the following parameters:
    lenmax=dd
       Where 'dd' is the maximum number of elements per array that should
       be printed.  If 'dd' is 0, all elements are printed (this is the
       default)
    colsize=ss
       Where 'ss' will be used as the default size for all the column
       If this options is not specified, the default column size is 9
    precision=pp
       Where 'pp' will be used as the default 'precision' for the
       printing format.
    col=xxx
       Where 'xxx' is colon (:) delimited list of printing format for
       each column if no format is specified for a column, the default is
       used.
 For example:
   tree->Scan("a:b:c","","colsize=30 precision=3 col=::20.10");
 Will print 3 columns, the first 2 columns will be 30 characters long,
 the third columns will be 20 characters long.  The
 for the columns (assuming they are numbers) will be respectively:
   %30.3g %30.3g %20.10g

 Loop on Tree and return TSQLResult object containing entries passing
 selection. If varexp is 0 (or "") then print only first 8 columns.
 If varexp = "*" print all columns. Otherwise a columns selection can
 be made using "var1:var2:var3". In case of error 0 is returned otherwise
 a TSQLResult object which must be deleted by the user.

*-*-*-*-*-*-*-*-*Set number of entries to estimate variable limits*-*-*-*
*-*              ================================================

*-*-*-*-*-*-*-*-*Start the TTreeViewer on this TTree*-*-*-*-*-*-*-*-*-*
*-*              ===================================

  ww is the width of the canvas in pixels
  wh is the height of the canvas in pixels

*-*-*-*-*-*Unbinned fit of one or more variable(s) from a Tree*-*-*-*-*-*
*-*        ===================================================

  funcname is a TF1 function.

  See TTree::Draw for explanations of the other parameters.

   Fit the variable varexp using the function funcname using the
   selection cuts given by selection.

   The list of fit options is given in parameter option.
      option = "Q" Quiet mode (minimum printing)
             = "V" Verbose mode (default is between Q and V)
             = "E" Perform better Errors estimation using Minos technique
             = "M" More. Improve fit results
             = "D" Draw the projected histogram with the fitted function
                   normalized to the number of selected rows
                   and multiplied by the bin width

   You can specify boundary limits for some or all parameters via
        func->SetParLimits(p_number, parmin, parmax);
   if parmin>=parmax, the parameter is fixed
   Note that you are not forced to fix the limits for all parameters.
   For example, if you fit a function with 6 parameters, you can do:
     func->SetParameters(0,3.1,1.e-6,0.1,-8,100);
     func->SetParLimits(4,-10,-4);
     func->SetParLimits(5, 1,1);
   With this setup, parameters 0->3 can vary freely
   Parameter 4 has boundaries [-10,-4] with initial value -8
   Parameter 5 is fixed to 100.

   For the fit to be meaningful, the function must be self-normalized.

   i.e. It must have the same integral regardless of the parameter
   settings.  Otherwise the fit will effectively just maximize the
   area.

   It is mandatory to have a normalization variable
   which is fixed for the fit.  e.g.

     TF1* f1 = new TF1("f1", "gaus(0)/sqrt(2*3.14159)/[2]", 0, 5);
     f1->SetParameters(1, 3.1, 0.01);
     f1->SetParLimits(0, 1, 1); // fix the normalization parameter to 1
     data->UnbinnedFit("f1", "jpsimass", "jpsipt>3.0");
   

   1, 2 and 3 Dimensional fits are supported.
   See also TTree::Fit

 this function is called by TChain::LoadTree when a new Tree is loaded.
 Because Trees in a TChain may have a different list of leaves, one
 must update the leaves numbers in the TTreeFormula used by the TreePlayer.

Inline Functions

                 void TakeAction(Int_t nfill, Int_t& npoints, Int_t& action, TObject* obj, Option_t* option)
                 void TakeEstimate(Int_t nfill, Int_t& npoints, Int_t action, TObject* obj, Option_t* option)
                Int_t GetDimension() const
                 TH1* GetHistogram() const
                Int_t GetNfill() const
          const char* GetScanFileName() const
        TTreeFormula* GetSelect() const
             Long64_t GetSelectedRows() const
           TSelector* GetSelector() const
        TTreeFormula* GetVar1() const
        TTreeFormula* GetVar2() const
        TTreeFormula* GetVar3() const
        TTreeFormula* GetVar4() const
            Double_t* GetV1() const
            Double_t* GetV2() const
            Double_t* GetV3() const
            Double_t* GetV4() const
            Double_t* GetW() const
               Bool_t ScanRedirected()
                 void SetScanRedirect(Bool_t on = kFALSE)
                 void SetScanFileName(const char* name)
                 void SetTree(TTree* t)
              TClass* Class()
              TClass* IsA() const
                 void ShowMembers(TMemberInspector& insp, char* parent)
                 void Streamer(TBuffer& b)
                 void StreamerNVirtual(TBuffer& b)
          TTreePlayer TTreePlayer(const TTreePlayer&)