directlabels - utility.function - Positioning Method - label.pieces

Make a Positioning Method that will, for every piece, select points and assign a vjust value.

label.pieces <- function(FUN,VJUST){
  function(d,...){
    processed <- gapply(d,function(d,...)d[FUN(d$y),],groups="piece")
    transform(processed,hjust=0.5,vjust=VJUST)
  }
}