Count observations by group

`count()` lets you quickly count the unique values of one or more variables: `df `df `count()` is paired with `tally()`, a lower-level helper that is equivalent to `df switching the summary from `n = n()` to `n = sum(wt)`.

`add_count()` are `add_tally()` are equivalents to `count()` and `tally()` but use `mutate()` instead of `summarise()` so that they add a new column with group-wise counts.

count(
  x,
  ...,
  wt = NULL,
  sort = FALSE,
  name = NULL,
  .drop = group_by_drop_default(x)
)

add_count(
  x,
  ...,
  wt = NULL,
  sort = FALSE,
  name = NULL,
  .drop = group_by_drop_default(x)
)

# S3 method for default
add_count(
  x,
  ...,
  wt = NULL,
  sort = FALSE,
  name = NULL,
  .drop = group_by_drop_default(x)
)

# S3 method for Seurat
add_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`][dplyr_data_masking]> Variables to group by.

wt

<[`data-masking`][dplyr_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 error, and require you to specify the name.

.drop

For `count()`: if `FALSE` will include counts for empty groups (i.e. for levels of factors that don't exist in the data). Deprecated in `add_count()` since it didn't actually affect the output.

Value

An object of the same type as `.data`. `count()` and `add_count()` group transiently, so the output has the same groups as the input.

Examples

`%>%` = magrittr::`%>%`
data("pbmc_small")
pbmc_small %>%  count(groups)
#> tidyseurat says: A data frame is returned for independent data analysis.
#> # A tibble: 2 × 2
#>   groups     n
#>   <chr>  <int>
#> 1 g1        44
#> 2 g2        36