Summarise each group down to one row

Source: R/summarise-rd.R, R/summarise.R

This is a method for the dplyr::summarise() generic. See "Fallbacks" section for differences in implementation. summarise() creates a new data frame. It returns one row for each combination of grouping variables; if there are no grouping variables, the output will have a single row summarising all observations in the input. It will contain one column for each grouping variable and one column for each of the summary statistics that you have specified.

# S3 method for class 'duckplyr_df'
summarise(.data, ..., .by = NULL, .groups = NULL)

Arguments

.data

A data frame, data frame extension (e.g. a tibble), or a lazy data frame (e.g. from dbplyr or dtplyr). See Methods, below, for more details.

...

<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, to add multiple columns from a single expression.

[Deprecated] Returning values with size 0 or >1 was deprecated as of 1.1.0. Please use reframe() for this instead.

.by

[Experimental]

<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

[Experimental] Grouping structure of the result.

  • "drop_last": dropping 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 chosen based on the number of rows of the results:

  • If all the results have 1 row, you get "drop_last".

  • If the number of rows varies, you get "keep" (note that returning a variable number of rows was deprecated in favor of reframe(), which also unconditionally drops all levels of grouping).

In addition, a message informs you of that choice, 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.

Fallbacks

There is no DuckDB translation in summarise.duckplyr_df()

  • with .groups = "rowwise".

These features fall back to dplyr::summarise(), see vignette("fallback") for details.

Examples

library(duckplyr)
summarise(mtcars, mean = mean(disp), n = n())
#>       mean  n
#> 1 230.7219 32