context function

Information about the "current" group or variable

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().

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))))