Drop unused levels

Source: R/drop.R

Compared to base::droplevels(), does not drop NA levels that have values.

fct_drop(f, only)

Arguments

f

A factor (or character vector).
only

A character vector restricting the set of levels to be dropped. If supplied, only levels that have no entries and appear in this vector will be removed.

See also

fct_expand() to add additional levels to a factor.

Examples

f <- factor(c("a", "b"), levels = c("a", "b", "c"))
f
#> [1] a b
#> Levels: a b c
fct_drop(f)
#> [1] a b
#> Levels: a b

# Set only to restrict which levels to drop
fct_drop(f, only = "a")
#> [1] a b
#> Levels: a b c
fct_drop(f, only = "c")
#> [1] a b
#> Levels: a b