context: Information about the "current" group or variable

In hadley/dplyr: A Grammar of Data Manipulation

Information about the "current" group or variable

Description

These functions return information about the "current" group or "current" variable, so only work inside specific contexts like summarise() and mutate().

• n() gives the current group size.

• cur_group() gives the group keys, a tibble with one row and one column for each grouping variable.

• cur_group_id() gives a unique numeric identifier for the current group.

• cur_group_rows() gives the row indices for the current group.

• cur_column() gives the name of the current column (in across() only).

See group_data() for equivalent functions that return values for all groups.

See pick() for a way to select a subset of columns using tidyselect syntax while inside summarise() or mutate().

Usage

n()

cur_group()

cur_group_id()

cur_group_rows()

cur_column()

data.table

If you're familiar with data.table:

• cur_group_id() <-> .GRP

• cur_group() <-> .BY

• cur_group_rows() <-> .I

See pick() for an equivalent to .SD.

Examples

df <- tibble(
  g = sample(rep(letters[1:3], 1:3)),
  x = runif(6),
  y = runif(6)
)
gf <- df %>% group_by(g)

gf %>% summarise(n = n())

gf %>% mutate(id = cur_group_id())
gf %>% reframe(row = cur_group_rows())
gf %>% summarise(data = list(cur_group()))

gf %>% mutate(across(everything(), ~ paste(cur_column(), round(.x, 2))))

hadley/dplyr documentation built on Nov. 6, 2024, 4:48 p.m.