Count observations by group

Analogous function for count and add_count in dplyr, wrapped directly from maditr.

count_dt(data, ..., weight = NULL, sort = FALSE, name = "n")

add_count_dt(data, ..., weight = NULL, sort = FALSE, name = "n")

Arguments

data	data.table/data.frame data.frame will be automatically converted to data.table.
...	variables to group by.
weight	optional. Unquoted variable name. If provided result will be the sum of this variable by groups.
sort	logical. If TRUE result will be sorted in desending order by resulting variable.
name	character. Name of resulting variable.

Value

data.table

See also

count,dt_count

Examples

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