RooCurve

 Create a 1-dim curve of the value of the specified real-valued expression
 as a function of x. Use the optional precision parameter to control
 how precisely the smooth curve is rasterized. Use the optional argument set
 to specify how the expression should be normalized. Use the optional scale
 factor to rescale the expression after normalization.
 If shiftToZero is set, the entire curve is shift down to make the lowest
 point in of the curve go through zero.
 grab the function's name and title

 Perform initialization that is common to all constructors.

 Find lowest point in curve and move all points in curve so that
 lowest point will go exactly through zero

 Add points calculated with the specified function, over the range (xlo,xhi).
 Add at least minPoints equally spaced points, and add sufficient points so that
 the maximum deviation from the final straight-line segements is prec*(ymax-ymin),
 down to a minimum horizontal spacing of resolution*(xhi-xlo).
 check the inputs

 Fill the range (x1,x2) with points calculated using func(&x). No point will
 be added at x1, and a point will always be added at x2. The density of points
 will be calculated so that the maximum deviation from a straight line
 approximation is prec*(ymax-ymin) down to the specified minimum horizontal spacing.
 calculate our value at the midpoint of this range

 Add a point with the specified coordinates. Update our y-axis limits.

 Print info about this histogram to the specified output stream.

   Standard: number of entries
    Verbose: print points on curve

 Average curve between given values by integrating curve between points
 and dividing by xLast-xFirst

 Find best point