group_modify.dtplyr_step: Apply a function to each group

In dtplyr: Data Table Back-End for 'dplyr'

Apply a function to each group

Description

These are methods for the dplyr dplyr::group_map() and dplyr::group_modify() generics. They are both translated to ⁠[.data.table⁠.

Usage

## S3 method for class 'dtplyr_step'
group_modify(.data, .f, ..., keep = FALSE)

## S3 method for class 'dtplyr_step'
group_map(.data, .f, ..., keep = FALSE)

Arguments

.data	A lazy_dt()
.f	The name of a two argument function. The first argument is passed .SD,the data.table representing the current group; the second argument is passed .BY, a list giving the current values of the grouping variables. The function should return a list or data.table.
...	Additional arguments passed to .f
keep	Not supported for lazy_dt.

Value

group_map() applies .f to each group, returning a list. group_modify() replaces each group with the results of .f, returning a modified lazy_dt().

Examples

library(dplyr)

dt <- lazy_dt(mtcars)

dt %>%
  group_by(cyl) %>%
  group_modify(head, n = 2L)

dt %>%
  group_by(cyl) %>%
  group_map(head, n = 2L)

dtplyr documentation built on Sept. 11, 2025, 1:07 a.m.