forcats (version 0.5.2)

fct: Create a factor

Description

fct() is a stricter version of factor() that errors if your specification of levels is inconsistent with the values in x.

Usage

fct(x = character(), levels = NULL, na = character())

Value

A factor.

Arguments

x

A character vector. Values must occur in either levels or na.

levels

A character vector of known levels. If not supplied, will be computed from the unique values of x, in the order in which they occur.

na

A character vector of values that should become missing values.

Examples

# Use factors when you know the set of possible values a variable might take
x <- c("A", "O", "O", "AB", "A")
fct(x, levels = c("O", "A", "B", "AB"))

# If you don't specify the levels, fct will create from the data
# in the order that they're seen
fct(x)


# Differences with base R -----------------------------------------------
# factor() silently generates NAs
x <- c("a", "b", "c")
factor(x, levels = c("a", "b"))
# fct() errors
try(fct(x, levels = c("a", "b")))
# Unless you explicitly supply NA:
fct(x, levels = c("a", "b"), na = "c")

# factor() sorts default levels:
factor(c("y", "x"))
# fct() uses in order of appearance:
fct(c("y", "x"))