top_n {dplyr} | R Documentation |
This is a convenient wrapper that uses filter()
and
min_rank()
to select the top or bottom entries in each group,
ordered by wt
.
top_n(x, n, wt) top_frac(x, n, wt)
x |
a |
n |
number of rows to return for If If |
wt |
(Optional). The variable to use for ordering. If not specified, defaults to the last variable in the tbl. |
Both n
and wt
are automatically quoted and later
evaluated in the context of the data
frame. It supports unquoting.
df <- data.frame(x = c(10, 4, 1, 6, 3, 1, 1)) df %>% top_n(2) # half the rows df %>% top_n(n() * .5) df %>% top_frac(.5) # 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 tbl_df(Batting) %>% group_by(playerID) %>% tally(G) %>% top_n(10) # Find year with most games for each player ## Not run: tbl_df(Batting) %>% group_by(playerID) %>% top_n(1, G) ## End(Not run) }