dplyr (version 0.1.1)

tally: Tally observations by group.

Description

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

Usage

tally(x, wt, sort = FALSE)

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.

sort

if TRUE will sort output in descending order of n

Examples

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

  # Multiple tallys progressively role up the groups
  plays_by_year <- tally(group_by(batting_tbl, playerID, stint), sort = TRUE)
  tally(plays_by_year, sort = TRUE)
  tally(tally(plays_by_year))

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