Combine Levels from Multiple Inputs

Extracts and combines the levels from one or more vectors or factors. Non-factor inputs are coerced to factors before extracting levels.

Usage

combLevels(..., sorted = FALSE, na = FALSE)

Arguments

...

one or more vectors or factors.

sorted

logical; if TRUE, the resulting levels are sorted.

na

logical; if TRUE, NA is treated as a valid level (i.e., included in the result).

Value

a character vector containing the unique levels across all inputs.

Details

Each input is coerced to a factor (if not already one), and its levels are extracted. The union of all levels is returned. Unused levels of factor inputs are preserved.

By default, missing values (NA) are not included as a level. Set na = TRUE to include them; NA is then placed last when sorting.

The order of levels follows their first occurrence unless sorted = TRUE.

See also

Other data.recode: asBinary(), dummy(), mReplace(), nf(), recodeX(), revCode(), stringsAsFactors()

Examples

x <- factor(c("A", "B"))
y <- c("B", "C")

combLevels(x, y)
#> [1] "A" "B" "C"

# Sorted levels
combLevels(x, y, sorted = TRUE)
#> [1] "A" "B" "C"

# Including NA as a level
x <- c("A", NA)
y <- c("B", NA)
combLevels(x, y, na = TRUE)
#> [1] "A" NA  "B"