class TF3: public TF2

 F3 default constructor.

 F3 constructor using a formula definition.

  See TFormula constructor for explanation of the formula syntax.

 F3 constructor using a pointer to real function.

   npar is the number of free parameters used by the function

  For example, for a 3-dim function with 3 parameters, the user function
      looks like:
    Double_t fun1(Double_t *x, Double_t *par)
        return par[0]*x[2] + par[1]*exp(par[2]*x[0]*x[1]);

 WARNING! A function created with this constructor cannot be Cloned.

 F3 constructor using a pointer to real function.

   npar is the number of free parameters used by the function

  For example, for a 3-dim function with 3 parameters, the user function
      looks like:
    Double_t fun1(Double_t *x, Double_t *par)
        return par[0]*x[2] + par[1]*exp(par[2]*x[0]*x[1]);

 WARNING! A function created with this constructor cannot be Cloned.

 F3 constructor using a ParamFunctor,
          a functor class implementing operator() (double *, double *)

   npar is the number of free parameters used by the function

 WARNING! A function created with this constructor cannot be Cloned.

 Operator =

 F3 default destructor.

 Copy constructor.

 Copy this F3 to a new F3.

 Compute distance from point px,py to a function.

  Compute the closest distance of approach from point px,py to this function.
  The distance is computed in pixels units.

 Draw this function with its current attributes.

 Execute action corresponding to one event.

  This member function is called when a F3 is clicked with the locator

 return minimum/maximum value of the function
 To find the minimum on a range, first set this range via the SetRange function
 If a vector x of coordinate is passed it will be used as starting point for the minimum.
 In addition on exit x will contain the coordinate values at the minimuma
 If x is NULL or x is inifinity or NaN, first, a grid search is performed to find the initial estimate of the
 minimum location. The range of the function is divided into fNpx and fNpy
 sub-ranges. If the function is "good" (or "bad"), these values can be changed
 by SetNpx and SetNpy functions
 Then, a minimization is used with starting values found by the grid search
 The minimizer algorithm used (by default Minuit) can be changed by callinga
  ROOT::Math::Minimizer::SetDefaultMinimizerType("..")
 Other option for the minimizer can be set using the static method of the MinimizerOptions class

 Compute the X, Y and Z values corresponding to the minimum value of the function
 on its range. Return the function value at the minimum
 To find the minimum on a subrange, use the SetRange() function first.
 Method:
   First, a grid search is performed to find the initial estimate of the
   minimum location. The range of the function is divided
   into fNpx,fNpy and fNpz sub-ranges. If the function is "good" (or "bad"),
   these values can be changed by SetNpx(), SetNpy() and SetNpz() functions.
   Then, Minuit minimization is used with starting values found by the grid search

   Note that this method will always do first a grid search in contrast to GetMinimum

 Compute the X, Y and Z values corresponding to the maximum value of the function
 on its range. Return the function value at the maximum
 See TF3::GetMinimumXYZ

 Return 3 random numbers following this function shape.

   The distribution contained in this TF3 function is integrated
   over the cell contents.
   It is normalized to 1.
   Getting the three random numbers implies:
     - Generating a random number between 0 and 1 (say r1)
     - Look in which cell in the normalized integral r1 corresponds to
     - make a linear interpolation in the returned cell


  IMPORTANT NOTE
  The integral of the function is computed at fNpx * fNpy * fNpz points.
  If the function has sharp peaks, you should increase the number of
  points (SetNpx, SetNpy, SetNpz) such that the peak is correctly tabulated
  at several points.

 Return range of function.

 Get value corresponding to X in array of fSave values

 Return Integral of a 3d function in range [ax,bx],[ay,by],[az,bz]
 with a desired relative accuracy.

 Return kTRUE is the point is inside the function range

 Create a histogram for axis range.

 Paint this 3-D function with its current attributes.

 Set the function clipping box (for drawing) "off".

 Save values of function in array fSave

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

 Set the function clipping box (for drawing) "on" and define the clipping box.
 xclip, yclip and zclip is a point within the function range. All the
 function values having x<=xclip and y<=yclip and z>=zclip are clipped.

 Set the number of points used to draw the function

 The default number of points along x is 30 for 2-d/3-d functions.
 You can increase this value to get a better resolution when drawing
 pictures with sharp peaks or to get a better result when using TF3::GetRandom2
 the minimum number of points is 4, the maximum is 10000 for 2-d/3-d functions

 Initialize the upper and lower bounds to draw the function.

 Stream an object of class TF3.

 Return x^nx * y^ny * z^nz moment of a 3d function in range [ax,bx],[ay,by],[az,bz]
   Author: Gene Van Buren <gene@bnl.gov>

 Return x^nx * y^ny * z^nz central moment of a 3d function in range [ax,bx],[ay,by],[az,bz]
   Author: Gene Van Buren <gene@bnl.gov>