FUNCTION: LieTools/E2R
USAGE: R2E(i,Gt); R2E(i); R2E(i,Gtype,rnk);
SYNOPSIS: routines to convert root labeling from from 1 to nrts to 
  root labeling from -nprts to nprts. When called with a single argument
  i, it is necessary to first initialize a global Lie algebra environment
  (see LieTools[gSetup]).
EXAMPLE: 
> LieTools[R2E](1,G2);

                                  -6


SEE ALSO: LieTools[E2R], LieTools[E2G], LieTools[G2E]
