stabilize_fct: Ensure a factor argument meets expectations

In stbl: Stabilize Function Arguments

Ensure a factor argument meets expectations

Description

to_fct() checks whether an argument can be coerced to a factor without losing information, returning it silently if so. Otherwise an informative error message is signaled.

stabilize_fct() can check more details about the argument, but is slower than to_fct().

stabilize_fct_scalar() and to_fct_scalar() are optimized to check for length-1 factors.

Usage

stabilize_fct(
  x,
  ...,
  allow_null = TRUE,
  allow_na = TRUE,
  min_size = NULL,
  max_size = NULL,
  levels = NULL,
  to_na = character(),
  x_arg = caller_arg(x),
  call = caller_env(),
  x_class = object_type(x)
)

stabilize_fct_scalar(
  x,
  ...,
  allow_null = TRUE,
  allow_zero_length = TRUE,
  allow_na = TRUE,
  levels = NULL,
  to_na = character(),
  x_arg = caller_arg(x),
  call = caller_env(),
  x_class = object_type(x)
)

to_fct(
  x,
  ...,
  levels = NULL,
  to_na = character(),
  x_arg = caller_arg(x),
  call = caller_env(),
  x_class = object_type(x)
)

## S3 method for class ''NULL''
to_fct(x, ..., allow_null = TRUE, x_arg = caller_arg(x), call = caller_env())

to_fct_scalar(
  x,
  ...,
  allow_null = TRUE,
  allow_zero_length = TRUE,
  levels = NULL,
  to_na = character(),
  x_arg = caller_arg(x),
  call = caller_env(),
  x_class = object_type(x)
)

Arguments

x	The argument to stabilize.
...	Arguments passed to methods.
allow_null	⁠(length-1 logical)⁠ Is NULL an acceptable value?
allow_na	⁠(length-1 logical)⁠ Are NA values ok?
min_size	⁠(length-1 integer)⁠ The minimum size of the object. Object size will be tested using vctrs::vec_size().
max_size	⁠(length-1 integer)⁠ The maximum size of the object. Object size will be tested using vctrs::vec_size().
levels	(character) Expected levels. If NULL (default), the levels will be computed by base::factor().
to_na	(character) Values to convert to NA.
x_arg	⁠(length-1 character)⁠ An argument name for x. The automatic value will work in most cases, or pass it through from higher-level functions to make error messages clearer in unexported functions.
call	(environment) The execution environment to mention as the source of error messages.
x_class	⁠(length-1 character)⁠ The class name of x to use in error messages. Use this if you remove a special class from x before checking its coercion, but want the error message to match the original class.
allow_zero_length	⁠(length-1 logical)⁠ Are zero-length vectors acceptable?

Details

These functions have important differences from base::as.factor() and base::factor():

• Values are never silently coerced to NA unless they are explicitly supplied in the to_na argument.

• NULL values can be rejected as part of the call to this function (with allow_null = FALSE).

Value

The argument as a factor.

Examples

to_fct("a")
to_fct(1:10)
to_fct(NULL)
try(to_fct(letters[1:5], levels = c("a", "c"), to_na = "b"))

to_fct_scalar("a")
try(to_fct_scalar(letters))

stabilize_fct(letters)
try(stabilize_fct(NULL, allow_null = FALSE))
try(stabilize_fct(c("a", NA), allow_na = FALSE))
try(stabilize_fct(c("a", "b", "c"), min_size = 5))
try(stabilize_fct(c("a", "b", "c"), max_size = 2))

stabilize_fct_scalar("a")
try(stabilize_fct_scalar(letters))
try(stabilize_fct_scalar("c", levels = c("a", "b")))

stbl documentation built on Nov. 5, 2025, 6:02 p.m.