dplyr (version 0.5.0)

top_n: Select top (or bottom) n rows (by value).

Description

This is a convenient wrapper that uses filter and min_rank to select the top or bottom entries in each group, ordered by wt.

Usage

top_n(x, n, wt)

Arguments

x

a tbl to filter

n

number of rows to return. If x is grouped, this is the number of rows per group. Will include more than n rows if there are ties.

If n is positive, selects the top n rows. If negative, selects the bottom n rows.

wt

(Optional). The variable to use for ordering. If not specified, defaults to the last variable in the tbl.

Examples

df <- data.frame(x = c(10, 4, 1, 6, 3, 1, 1))
df %>% top_n(2)

# Negative values select bottom from group. Note that we get more
# than 2 values here because there's a tie: top_n() either takes
# all rows with a value, or none.
df %>% top_n(-2)

if (require("Lahman")) {
# Find 10 players with most games
# A little nicer with %>%
tbl_df(Batting) %>%
  group_by(playerID) %>%
  tally(G) %>%
  top_n(10)

# Find year with most games for each player
tbl_df(Batting) %>% group_by(playerID) %>% top_n(1, G)
}