dbplyr: summarise.tbl_lazy – R documentation

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summarise.tbl_lazy

Summarise each group to one row

Description

This is a method for the dplyr summarise() generic. It generates the SELECT clause of the SQL query, and generally needs to be combined with group_by().

Usage

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

Arguments

.data

A lazy data frame backed by a database query.

...

<data-masking> Variables, or functions of variables. Use desc() to sort a variable in descending order.

.groups

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.

When .groups is not specified, it defaults to "drop_last".

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.

Value

Another tbl_lazy. Use show_query() to see the generated query, and use collect() to execute the query and return data to R.

Examples

library(dplyr, warn.conflicts = FALSE)

db <- memdb_frame(g = c(1, 1, 1, 2, 2), x = c(4, 3, 6, 9, 2))
db %>%
  summarise(n()) %>%
  show_query()

db %>%
  group_by(g) %>%
  summarise(n()) %>%
  show_query()

dbplyr

A 'dplyr' Back End for Databases

v2.1.1

MIT + file LICENSE

Authors

Hadley Wickham [aut, cre], Maximilian Girlich [aut], Edgar Ruiz [aut], RStudio [cph, fnd]

Initial release