Note: All mfiles are from the folder http://www.math.unl.edu/~bdeng1/Teaching/math439/LectureNotes/mfilech1/
R(p) = (-p lg(p) (1-p) lg(1-p)) / (p+2(1-p))
in the interval [0,1]. It is the source rate function of a binary channel with symbol times 1, 2.