class TGraph2D: public TNamed, public TAttLine, public TAttFill, public TAttMarker

 Graph2D default constructor

 Graph2D constructor with three vectors of ints as input.

 Graph2D constructor with three vectors of floats as input.

 Graph2D constructor with three vectors of doubles as input.

 Graph2D constructor with a TH2 (h2) as input.
 Only the h2's bins within the X and Y axis ranges are used.
 Empty bins, recognized when both content and errors are zero, are excluded.

 Graph2D constructor with name, title and three vectors of doubles as input.
 name   : name of 2D graph (avoid blanks)
 title  : 2D graph title
          if title is of the form "stringt;stringx;stringy;stringz"
          the 2D graph title is set to stringt, the x axis title to stringx,
          the y axis title to stringy,etc

 Graph2D constructor. The arrays fX, fY and fZ should be filled via
 calls to SetPoint

 Graph2D constructor reading input from filename
 filename is assumed to contain at least three columns of numbers.
 For files separated by a specific delimiter different from ' ' and '\t' (e.g. ';' in csv files)
 you can avoid using %*s to bypass this delimiter by explicitly specify the "option" argument,
 e.g. option=" \t,;" for columns of figures separated by any of these characters (' ', '\t', ',', ';')
 used once (e.g. "1;1") or in a combined way (" 1;,;;  1").
 Note in that case, the instanciation is about 2 times slower.

 Graph2D copy constructor.
 copy everything apart from the list of contained functions

 TGraph2D destructor.

 Graph2D operator "="

 Creates the 2D graph basic data structure

 Browse

 Free all memory allocated by this object.

 Perform the automatic addition of the graph to the given directory

 Note this function is called in place when the semantic requires
 this object to be added to a directory (I.e. when being read from
 a TKey or being Cloned)

 Computes distance from point px,py to a graph

 Specific drawing options can be used to paint a TGraph2D:

   "TRI"  : The Delaunay triangles are drawn using filled area.
            An hidden surface drawing technique is used. The surface is
            painted with the current fill area color. The edges of each
            triangles are painted with the current line color.
   "TRIW" : The Delaunay triangles are drawn as wire frame
   "TRI1" : The Delaunay triangles are painted with color levels. The edges
            of each triangles are painted with the current line color.
   "TRI2" : the Delaunay triangles are painted with color levels.
   "P"    : Draw a marker at each vertex
   "P0"   : Draw a circle at each vertex. Each circle background is white.
   "PCOL" : Draw a marker at each vertex. The color of each marker is
            defined according to its Z position.
   "CONT" : Draw contours
   "LINE" : Draw a 3D polyline

 A TGraph2D can be also drawn with ANY options valid to draw a 2D histogram.

 When a TGraph2D is drawn with one of the 2D histogram drawing option,
 a intermediate 2D histogram is filled using the Delaunay triangles
 technique to interpolate the data set.

 Executes action corresponding to one event

 search object named name in the list of functions

 search object obj in the list of functions

 Fits this graph with function with name fname
 Predefined functions such as gaus, expo and poln are automatically
 created by ROOT.
 fname can also be a formula, accepted by the linear fitter (linear parts divided
 by "++" sign), for example "x++sin(y)" for fitting "[0]*x+[1]*sin(y)"

 Fits this 2D graph with function f2

  f2 is an already predefined function created by TF2.
  Predefined functions such as gaus, expo and poln are automatically
  created by ROOT.

  The list of fit options is given in parameter option.
     option = "W" Set all weights to 1; ignore error bars
            = "U" Use a User specified fitting algorithm (via SetFCN)
            = "Q" Quiet mode (minimum printing)
            = "V" Verbose mode (default is between Q and V)
            = "R" Use the Range specified in the function range
            = "N" Do not store the graphics function, do not draw
            = "0" Do not plot the result of the fit. By default the fitted function
                  is drawn unless the option "N" above is specified.
            = "+" Add this new fitted function to the list of fitted functions
                  (by default, any previous function is deleted)
            = "C" In case of linear fitting, not calculate the chisquare
                  (saves time)
            = "EX0" When fitting a TGraphErrors do not consider errors in the coordinate
            = "ROB" In case of linear fitting, compute the LTS regression
                     coefficients (robust (resistant) regression), using
                     the default fraction of good points
              "ROB=0.x" - compute the LTS regression coefficients, using
                           0.x as a fraction of good points
            = "S"  The result of the fit is returned in the TFitResultPtr
                     (see below Access to the Fit Result)

  In order to use the Range option, one must first create a function
  with the expression to be fitted. For example, if your graph2d
  has a defined range between -4 and 4 and you want to fit a gaussian
  only in the interval 1 to 3, you can do:
       TF2 *f2 = new TF2("f2","gaus",1,3);
       graph2d->Fit("f2","R");


  Setting initial conditions

  Parameters must be initialized before invoking the Fit function.
  The setting of the parameter initial values is automatic for the
  predefined functions : poln, expo, gaus. One can however disable
  this automatic computation by specifying the option "B".
  You can specify boundary limits for some or all parameters via
       f2->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.

  Fit range

  The fit range can be specified in two ways:
    - specify rxmax > rxmin (default is rxmin=rxmax=0)
    - specify the option "R". In this case, the function will be taken
      instead of the full graph range.

  Changing the fitting function

   By default a chi2 fitting function is used for fitting a TGraph.
   The function is implemented in FitUtil::EvaluateChi2.
   In case of TGraph2DErrors an effective chi2 is used
   (see TGraphErrors fit in TGraph::Fit) and is implemented in
   FitUtil::EvaluateChi2Effective
   To specify a User defined fitting function, specify option "U" and
   call the following functions:
   TVirtualFitter::Fitter(mygraph)->SetFCN(MyFittingFunction)
   where MyFittingFunction is of type:
   extern void MyFittingFunction(Int_t &npar, Double_t *gin, Double_t &f, Double_t *u, Int_t flag);

  Associated functions

  One or more object (typically a TF2*) can be added to the list
  of functions (fFunctions) associated to each graph.
  When TGraph::Fit is invoked, the fitted function is added to this list.
  Given a graph gr, one can retrieve an associated function
  with:  TF2 *myfunc = gr->GetFunction("myfunc");

  Access to the fit results

  The function returns a TFitResultPtr which can hold a  pointer to a TFitResult object.
  By default the TFitResultPtr contains only the status of the fit and it converts automatically to an
  integer. If the option "S" is instead used, TFitResultPtr contains the TFitResult and behaves as a smart
  pointer to it. For example one can do:
     TFitResultPtr r = graph->Fit("myFunc","S");
     TMatrixDSym cov = r->GetCovarianceMatrix();  //  to access the covariance matrix
     Double_t par0   = r->Value(0); // retrieve the value for the parameter 0
     Double_t err0   = r->Error(0); // retrieve the error for the parameter 0
     r->Print("V");     // print full information of fit including covariance matrix
     r->Write();        // store the result in a file

  The fit parameters, error and chi2 (but not covariance matrix) can be retrieved also
  from the fitted function.
  If the graph is made persistent, the list of
  associated functions is also persistent. Given a pointer (see above)
  to an associated function myfunc, one can retrieve the function/fit
  parameters with calls such as:
    Double_t chi2 = myfunc->GetChisquare();
    Double_t par0 = myfunc->GetParameter(0); //value of 1st parameter
    Double_t err0 = myfunc->GetParError(0);  //error on first parameter

  Fit Statistics

  You can change the statistics box to display the fit parameters with
  the TStyle::SetOptFit(mode) method. This mode has four digits.
  mode = pcev  (default = 0111)
    v = 1;  print name/values of parameters
    e = 1;  print errors (if e=1, v must be 1)
    c = 1;  print Chisquare/Number of degress of freedom
    p = 1;  print Probability

  For example: gStyle->SetOptFit(1011);
  prints the fit probability, parameter names/values, and errors.
  You can change the position of the statistics box with these lines
  (where g is a pointer to the TGraph):

  Root > TPaveStats *st = (TPaveStats*)g->GetListOfFunctions()->FindObject("stats")
  Root > st->SetX1NDC(newx1); //new x start position
  Root > st->SetX2NDC(newx2); //new x end position

 Display a GUI panel with all graph fit options.

   See class TFitEditor for example

 Get x axis of the graph.

 Get y axis of the graph.

 Get z axis of the graph.

 Returns the X and Y graphs building a contour. A contour level may
 consist in several parts not connected to each other. This function
 returns them in a graphs' list.

 This function is called by Graph2DFitChisquare.
 It always returns a negative value. Real implementation in TGraph2DErrors

 This function is called by Graph2DFitChisquare.
 It always returns a negative value. Real implementation in TGraph2DErrors

 This function is called by Graph2DFitChisquare.
 It always returns a negative value. Real implementation in TGraph2DErrors

 By default returns a pointer to the Delaunay histogram. If fHistogram
 doesn't exist, books the 2D histogram fHistogram with a margin around
 the hull. Calls TGraphDelaunay::Interpolate at each bin centre to build up
 an interpolated 2D histogram.
 If the "empty" option is selected, returns an empty histogram booked with
 the limits of fX, fY and fZ. This option is used when the data set is
 drawn with markers only. In that particular case there is no need to
 find the Delaunay triangles.

 Returns the X maximum

 Returns the X minimum

 Returns the Y maximum

 Returns the Y minimum

 Returns the Z maximum

 Returns the Z minimum

 Finds the z value at the position (x,y) thanks to
 the Delaunay interpolation.

 Paints this 2D graph with its current attributes

 Projects a 2-d graph into 1 or 2-d histograms depending on the
 option parameter
 option may contain a combination of the characters x,y,z
 option = "x" return the x projection into a TH1D histogram
 option = "y" return the y projection into a TH1D histogram
 option = "xy" return the x versus y projection into a TH2D histogram
 option = "yx" return the y versus x projection into a TH2D histogram

 Deletes point number ipoint

 Saves primitive as a C++ statement(s) on output stream out

 Set number of points in the 2D graph.
 Existing coordinates are preserved.
 New coordinates above fNpoints are preset to 0.

 By default when an 2D graph is created, it is added to the list
 of 2D graph objects in the current directory in memory.
 This method removes reference to this 2D graph from current directory and add
 reference to new directory dir. dir can be 0 in which case the
 2D graph does not belong to any directory.

 Sets the histogram to be filled.
 If the 2D graph needs to be save in a TFile the folllowing set should be
 followed to read it back:
 1) Create TGraph2D
 2) Call g->SetHistogram(h), and do whatever you need to do
 3) Save g and h to the TFile, exit
 4) Open the TFile, retrieve g and h
 5) Call h->SetDirectory(0)
 6) Call g->SetHistogram(h) again
 7) Carry on as normal

 Sets the extra space (in %) around interpolated area for the 2D histogram

 Sets the histogram bin height for points lying outside the TGraphDelaunay
 convex hull ie: the bins in the margin.

 Set maximum.

 Set minimum.

 Changes the name of this 2D graph

 Change the name and title of this 2D graph

 Sets the number of bins along X used to draw the function

 Sets the number of bins along Y used to draw the function

 Sets point number n.
 If n is greater than the current size, the arrays are automatically
 extended.

 Sets graph title

 Stream a class object