dplyr (version 0.5.0)

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. count() is similar, but also does the group_by for you.

Usage

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

Arguments

x

a tbl to tally/count.

wt

(Optional) If omitted, will count the number of rows. If specified, will perform a "weighted" tally by summing the (non-missing) values of variable wt.

sort

if TRUE will sort output in descending order of n

..., vars

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 roll 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)
}

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