Legendre Transformation of a one variable function

Given a function F and a vector x, returns two vectors of numbers xx=F'(x) and yy=F(x)-x*xx

[xx,yy]=legendretrans01(F,x,h,varargin)
Given a function F and a vector x, the corresponding points of the legendre
transformation are numerically approximated and stored in the vectors xx and yy, where
xx=F'(x) and yy=F(x)-xx*x
If F is not defined for vectors, a loop is used to evaluate it at each point on x

F'(x) is approximated by centered finite differences