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)

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)
#> grp N #> 1: 1 33465 #> 2: 2 33370 #> 3: 3 33165
dt_count(dt, grp, na.rm = TRUE)
#> grp N #> 1: 1 33465 #> 2: 2 33370 #> 3: 3 33165
dt_count(dt, grp, na.rm = TRUE, wt = wt)
#> grp N #> 1: 1 1691379 #> 2: 2 1683600 #> 3: 3 1677040