directlabels - utility.function - Positioning Method - dl.summarize

summarize which preserves important columns for direct labels.

dl.summarize <- function
### summarize which preserves important columns for direct labels.
(OLD,
### data frame
 ...
 ){
  rownames(OLD) <- NULL
  NEW <- unique(transform(OLD,...))
  to.copy <- names(OLD)[!names(OLD)%in%names(NEW)]
  for(N in to.copy)
    NEW[,N] <- OLD[,N]
  NEW
}