context: Context dependent expressions

In javifar/TIDYVERSE-DPLYR: A Grammar of Data Manipulation

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_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 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.

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

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 %>% 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))))

javifar/TIDYVERSE-DPLYR documentation built on Dec. 20, 2021, 9:08 p.m.