class RooEllipse: public TGraph, public RooPlotable

 Default constructor

 Destructor

 Create a 2-dimensional ellipse centered at (x1,x2) that represents the confidence
 level contour for a measurement with errors (s1,s2) and correlation coefficient rho.
 The resulting curve is defined as the unique ellipse that passes through these points:

   (x1+rho*s1,x2+s2) , (x1-rho*s1,x2-s2) , (x1+s1,x2+rho*s2) , (x1-s1,x2-rho*s2)

 and is described by the implicit equation:

   x*x      2*rho*x*y      y*y
  -----  -  ---------  +  -----  =  1 - rho*rho
  s1*s1       s1*s2       s2*s2

 The input parameters s1,s2 must be > 0 and also |rho| <= 1.
 The degenerate case |rho|=1 corresponds to a straight line and
 is handled as a special case.

 Print name of ellipse on ostream

 Print title of ellipse on ostream

 Print class name of ellipse on ostream

 Print detailed multi line information on ellipse on ostreamx

 Printing interface

 These methods return zero to indicate that they do not support
 this interface. See RooPlot::updateFitRangeNorm() for details.