dtplyr (version 1.3.3)

summarise.dtplyr_step: Summarise each group to one row

Description

This is a method for the dplyr dplyr::summarise() generic. It is translated to the j argument of [.data.table.

Usage

# S3 method for dtplyr_step
summarise(.data, ..., .by = NULL, .groups = NULL)

Arguments

.data

A lazy_dt().

...

<data-masking> Name-value pairs of summary functions. The name will be the name of the variable in the result.

The value can be:

• A vector of length 1, e.g. min(x), n(), or sum(is.na(y)).

• A data frame with 1 row, to add multiple columns from a single expression.

.by

<tidy-select> Optionally, a selection of columns to group by for just this operation, functioning as an alternative to group_by(). For details and examples, see ?dplyr_by.

.groups

Grouping structure of the result.

• "drop_last": drops the last level of grouping. This was the only supported option before version 1.0.0.

• "drop": All levels of grouping are dropped.

• "keep": Same grouping structure as .data.

• "rowwise": Each row is its own group.

When .groups is not specified, it is set to "drop_last" for a grouped data frame, and "keep" for a rowwise data frame. In addition, a message informs you of how the result will be grouped unless the result is ungrouped, the option "dplyr.summarise.inform" is set to FALSE, or when summarise() is called from a function in a package.

Examples

library(dplyr, warn.conflicts = FALSE)

dt <- lazy_dt(mtcars)

dt %>%
  group_by(cyl) %>%
  summarise(vs = mean(vs))

dt %>%
  group_by(cyl) %>%
  summarise(across(disp:wt, mean))