dplyr::count()

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

count() and tally() are dplyr verbs for counting observations. count() is a convenience wrapper that combines group_by() and summarise(n()) in one step. tally() adds a count column to a grouped tibble.

Syntax

count(x, ..., wt = NULL, sort = FALSE, .drop = TRUE)
tally(x, wt = NULL, sort = FALSE, name = "n")

Parameters

Parameter	Type	Default	Description
x	tibble/data.frame	required	The data to count
...	variables	optional	Variables to group by (count only)
wt	variable	NULL	Optional weighting variable — adds a weighted count instead of raw count
sort	logical	FALSE	If TRUE, sort output by count in descending order
.drop	logical	TRUE	If FALSE, include combinations with zero counts
name	string	"n"	Name of the count column (tally only)

Examples

Basic usage

library(dplyr)

# Simple count of all rows
mtcars |> tally()
# # A tibble: 1 × 1
#       n
#   <int>
# 1    32

Count by group

# Count cars by number of cylinders
mtcars |> count(cyl)
# # A tibble: 3 × 2
#     cyl     n
#   <dbl> <int>
# 1     4    11
# 2     6     7
# 3     8    14

Count by multiple groups

# Count by cylinders and gears
mtcars |> count(cyl, gear)
# # A tibble: 8 × 3
#     cyl  gear     n
#   <dbl> <dbl> <int>
# 1     4     3     1
# 2     4     4     7
# 3     4     5     3
# 4     6     3     2
# 5     6     4     4
# 6     6     5     1
# 7     8     3     5
# 8     8     5     9

Weighted counts

# Weight by horsepower - sum of hp per cylinder
mtcars |> count(cyl, wt = hp)
# # A tibble: 3 × 2
#     cyl     n
#   <dbl> <dbl>
# 1     4   908
# 2     6   761
# 3     8  2929

Using tally() with existing groups

# First group, then tally
mtcars |> group_by(cyl) |> tally()
# # A tibble: 3 × 2
#     cyl     n
#   <dbl> <int>
# 1     4    11
# 2     6     7
# 3     8    14

Sort by count

# Sort output in descending order
mtcars |> count(cyl, sort = TRUE)
# # A tibble: 3 × 2
#     cyl     n
#   <dbl> <int>
# 1     8    14
# 2     4    11
# 3     6     7

Common Patterns

Proportions from counts

# Add a proportion column
mtcars |> 
  count(cyl) |>
  mutate(prop = n / sum(n))
# # A tibble: 3 × 3
#     cyl     n   prop
#   <dbl> <int>  <dbl>
# 1     4    11 0.344 
# 2     6     7 0.219 
# 3     8    14 0.438 

Using with filter

# Find groups with more than N observations
mtcars |> count(cyl) |> filter(n > 10)
# # A tibble: 2 × 2
#     cyl     n
#   <dbl> <int>
# 1     4    11
# 2     8    14

Naming the count column

# Custom name for the count column
mtcars |> count(cyl, name = "total_cars")
# # A tibble: 3 × 2
#     cyl total_cars
#   <dbl>      <int>
# 1     4         11
# 2     6          7
# 3     8         14

See Also

• dplyr::group_by()
• dplyr::across()
• dplyr::filter()