group_modify.dtplyr_step {dtplyr}

Apply a function to each group

Description

These are methods for the dplyr group_map() and 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)