doBy - Groupwise summary statistics, LSmeans, general linear
contrasts, various utilities
Søren Højsgaard <sorenh@math.aau.dk> and Ulrich Halekoh <uhalekoh@health.sdu.dk> with contributions from Jim Robison-Cox, Kevin Wright, Alessandro A. Leidi and others.
doBy originally contained facilities to 'do' something to data stratified 'by' some variables. doBy contains a
 variety of utilities including:

   1) Facilities for groupwise computations of summary statistics and
 other facilities for working with grouped data.

   2) LSmeans (least-squares means), general linear contrasts.

   3) Miscellaneous other utilities.
pbkrtest (>= 0.3-8), ggplot2, multcomp, geepack, lme4