LetrGd(Grd,Lwl=c(90,80,70,60,0),LtGd=c("A","B","C","D","R"))

 Convert numeric values into letter grades


 Grd  is a numeric vector

 Lwl  is a numeric vector of lower levels, that is it 
      defines the inclusive lower limit of each grade.
      Lwl *must* be monotonically decreasing and it's length must
      match the length of LtGd (by default 5)

 LtGd is a chacter vector that defines the grade names.

 $Id: GdBkUtil.S,v 1.5 2000/02/02 21:31:53 nicholst Exp $