Count observations by group

Analogous function for count and add_count in dplyr.

count_dt(data, ..., sort = TRUE, name = "n")

add_count_dt(data, ..., name = "n")

Arguments

data	data.table/data.frame data.frame will be automatically converted to data.table.
...	variables to group by.
sort	logical. If TRUE result will be sorted in desending order by resulting variable.
name	character. Name of resulting variable. Default uses "n".

Value

data.table

See also

count

Examples

iris %>% count_dt(Species)
#>       Species  n
#> 1:     setosa 50
#> 2: versicolor 50
#> 3:  virginica 50
iris %>% count_dt(Species,name = "count")
#>       Species count
#> 1:     setosa    50
#> 2: versicolor    50
#> 3:  virginica    50
iris %>% add_count_dt(Species)
#>        Species Sepal.Length Sepal.Width Petal.Length Petal.Width  n
#>   1:    setosa          5.1         3.5          1.4         0.2 50
#>   2:    setosa          4.9         3.0          1.4         0.2 50
#>   3:    setosa          4.7         3.2          1.3         0.2 50
#>   4:    setosa          4.6         3.1          1.5         0.2 50
#>   5:    setosa          5.0         3.6          1.4         0.2 50
#>  ---                                                               
#> 146: virginica          6.7         3.0          5.2         2.3 50
#> 147: virginica          6.3         2.5          5.0         1.9 50
#> 148: virginica          6.5         3.0          5.2         2.0 50
#> 149: virginica          6.2         3.4          5.4         2.3 50
#> 150: virginica          5.9         3.0          5.1         1.8 50
iris %>% add_count_dt(Species,name = "N")
#>        Species Sepal.Length Sepal.Width Petal.Length Petal.Width  N
#>   1:    setosa          5.1         3.5          1.4         0.2 50
#>   2:    setosa          4.9         3.0          1.4         0.2 50
#>   3:    setosa          4.7         3.2          1.3         0.2 50
#>   4:    setosa          4.6         3.1          1.5         0.2 50
#>   5:    setosa          5.0         3.6          1.4         0.2 50
#>  ---                                                               
#> 146: virginica          6.7         3.0          5.2         2.3 50
#> 147: virginica          6.3         2.5          5.0         1.9 50
#> 148: virginica          6.5         3.0          5.2         2.0 50
#> 149: virginica          6.2         3.4          5.4         2.3 50
#> 150: virginica          5.9         3.0          5.1         1.8 50