Count the observations in each group

This is a method for the dplyr::count() generic. See "Fallbacks" section for differences in implementation. count() lets you quickly count the unique values of one or more variables: df %>% count(a, b) is roughly equivalent to df %>% group_by(a, b) %>% summarise(n = n()). count() is paired with tally(), a lower-level helper that is equivalent to df %>% summarise(n = n()). Supply wt to perform weighted counts, switching the summary from n = n() to n = sum(wt).

Usage

# S3 method for class 'duckplyr_df'
count(
  x,
  ...,
  wt = NULL,
  sort = FALSE,
  name = NULL,
  .drop = group_by_drop_default(x)
)

Arguments

x

A data frame, data frame extension (e.g. a tibble), or a lazy data frame (e.g. from dbplyr or dtplyr).

...

<data-masking> Variables to group by.

wt

<data-masking> Frequency weights. Can be NULL or a variable:

If NULL (the default), counts the number of rows in each group.
If a variable, computes sum(wt) for each group.

sort

If TRUE, will show the largest groups at the top.

name

The name of the new column in the output.

If omitted, it will default to n. If there's already a column called n, it will use nn. If there's a column called n and nn, it'll use nnn, and so on, adding ns until it gets a new name.

.drop

Handling of factor levels that don't appear in the data, passed on to group_by().

For count(): if FALSE will include counts for empty groups (i.e. for levels of factors that don't exist in the data).

For add_count(): deprecated since it can't actually affect the output.

Fallbacks

There is no DuckDB translation in count.duckplyr_df()

with complex expressions in ...,
with .drop = FALSE,
with sort = TRUE.

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

Examples

library(duckplyr)
count(mtcars, am)
#>   am  n
#> 1  0 19
#> 2  1 13

Usage

Arguments

Fallbacks

See also

Examples