Count — dt_count • tidyfast

Count the numbers of observations within groups

dt_count(dt_, ..., na.rm = FALSE, wt = NULL)

Arguments

dt_: the data table to uncount
...: groups
na.rm: should any rows with missingness be removed before the count? Default is FALSE.
wt: the wt assigned to the counts (same number of rows as the data)

Value

A data.table with counts for each group (or combination of groups)

Examples


library(data.table)
dt <- data.table(
  x = rnorm(1e5),
  y = runif(1e5),
  grp = sample(1L:3L, 1e5, replace = TRUE),
  wt = runif(1e5, 1, 100)
)

dt_count(dt, grp)
#> Key: <grp>
#>      grp     N
#>    <int> <int>
#> 1:     1 33215
#> 2:     2 33623
#> 3:     3 33162
dt_count(dt, grp, na.rm = TRUE)
#> Key: <grp>
#>      grp     N
#>    <int> <int>
#> 1:     1 33215
#> 2:     2 33623
#> 3:     3 33162
dt_count(dt, grp, na.rm = TRUE, wt = wt)
#> Key: <grp>
#>      grp       N
#>    <int>   <num>
#> 1:     1 1679015
#> 2:     2 1704372
#> 3:     3 1662926