dplyr (version 0.3)

tally: Counts/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. tally() is similar, but also does the group_by for you.

Usage

tally(x, wt, sort = FALSE)
count(x, ..., wt = NULL, sort = FALSE)

Arguments

x

a tbl to tally/count.

wt

(Optional) 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

...

Variables to group by.

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)

# count is even more succinct - it also does the grouping for you
batting_tbl %>% count(playerID)
batting_tbl %>% count(playerID, wt = G)
batting_tbl %>% count(playerID, wt = G, sort = TRUE)
}