context: Context dependent expressions

In nathaneastwood/poorman: A Poor Man's Dependency Free Recreation of 'dplyr'

Context dependent expressions

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 number of observations in the current group.

• cur_data() gives the current data for the current group (excluding grouping variables).

• cur_data_all() gives the current data for the current group (including grouping variables).

• cur_group() gives the group keys, a single row data.frame containing a column for each grouping variable and its value.

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

• cur_group_rows() gives the rows the groups appear in the data.

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

Usage

n()

cur_data()

cur_data_all()

cur_group()

cur_group_id()

cur_group_rows()

cur_column()

data.table

If you're familiar with data.table:

• cur_data() <-> .SD

• cur_group_id() <-> .GRP

• cur_group() <-> .BY

• cur_group_rows() <-> .I

See Also

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

Examples

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

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

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

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

nathaneastwood/poorman documentation built on Feb. 10, 2024, 1:41 p.m.