Count function

[hadley]

Maybe something like this:

count <- function(tbl, ..., wt = NULL) {
  vars <- dots(...)
  wt <- substitute(wt)

  grouped <- regroup(tbl, vars)
  if (is.null(wt)) {
    summarise(grouped, n = n())
  } else {
    call <- substitute(summarise(grouped, n = sum(wt)), list(wt = wt))
    eval(call)
  }
}

[hadley]

Should be something like this:

count <- function(tbl, ..., wt = NULL, sort = FALSE) {
  vars <- lazyeval::dots(...)
  wt <- substitute(wt)

  count_(tbl, vars, wt, sort = sort)
}

count_ <- function(tbl, ..., wt = NULL, sort = FALSE) {
  grouped <- group_by_(tbl, vars)
  tally_(grouped, wt = wt, sort = sort)  
}