parse_factor is similar to factor(), but will generate warnings if elements of x are not found in levels.

parse_factor(x, levels, ordered = FALSE, na = c("", "NA"),
  locale = default_locale(), include_na = TRUE)

col_factor(levels, ordered = FALSE, include_na = FALSE)


Character vector of values to parse.
Character vector providing set of allowed levels. if NULL, will generate levels based on the unique values of x, ordered by order of appearance in x.
Is it an ordered factor?
Character vector of strings to use for missing values. Set this option to character() to indicate no missing values.
The locale controls defaults that vary from place to place. The default locale is US-centric (like R), but you can use locale() to create your own locale that controls things like the default time zone, encoding, decimal mark, big mark, and day/month names.
If NA are present, include as an explicit factor to level?

See also

Other parsers: col_skip, parse_datetime, parse_guess, parse_logical, parse_number


parse_factor(c("a", "b"), letters)
#> [1] a b #> Levels: a b c d e f g h i j k l m n o p q r s t u v w x y z
x <- c("cat", "dog", "caw") levels <- c("cat", "dog", "cow") # Base R factor() silently converts unknown levels to NA x1 <- factor(x, levels) # parse_factor generates a warning & problems x2 <- parse_factor(x, levels)
#> Warning: 1 parsing failure. #> row col expected actual #> 3 -- value in level set caw
# Using an argument of `NULL` will generate levels based on values of `x` x2 <- parse_factor(x, levels = NULL)