dplyr (version 0.1)

tally: Tally observations by group.

Description

tally is a convenient wrapper for summarise that either call n or sum(n) depending on whether you're tallying for the first time, or re-tallying.

Usage

tally(x, wt)

Arguments

x

a tbl to tally

wt

if not specified, will tally the number of rows. If specified, will perform a "weighted" tally but summing over the specified variable.

Examples

if (require("Lahman")) {
  batting_tbl <- tbl_df(Batting)
  tally(group_by(batting_tbl, yearID))

  plays_by_year <- tally(group_by(batting_tbl, playerID, stint))
  tally(plays_by_year)
  # FIXME: https://github.com/hadley/dplyr/issues/129
  # tally(tally(plays_by_year))
  tally(group_by(plays_by_year, stint))

  # This looks a little nicer if you use the infix %.% operator
  batting_tbl %.% group_by(playerID) %.% tally()
}