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Ensure a factor argument meets expectations

Source: R/stabilize_fct.R, R/to_fct.R
stabilize_fct.Rd

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?

Value

The argument as a factor.

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).

Examples

to_fct("a")
#> [1] a
#> Levels: a
to_fct(1:10)
#>  [1] 1  2  3  4  5  6  7  8  9  10
#> Levels: 1 2 3 4 5 6 7 8 9 10
to_fct(NULL)
#> NULL
try(to_fct(letters[1:5], levels = c("a", "c"), to_na = "b"))
#> Error in eval(expr, envir) : 
#>   All values of `letters[1:5]` must be present in `levels` or `to_na`.
#> ℹ Disallowed values: d and e
#> ℹ Allowed values: a and c
#> ℹ Values that will be converted to `NA`: b

to_fct_scalar("a")
#> [1] a
#> Levels: a
try(to_fct_scalar(letters))
#> Error in eval(expr, envir) : 
#>   `letters` must be a single <factor>.
#> ✖ `letters` has 26 values.

stabilize_fct(letters)
#>  [1] 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
#> 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
try(stabilize_fct(NULL, allow_null = FALSE))
#> Error in eval(expr, envir) : `NULL` must not be <NULL>.
try(stabilize_fct(c("a", NA), allow_na = FALSE))
#> Error in eval(expr, envir) : 
#>   `c("a", NA)` must not contain NA values.
#> • NA locations: 2
try(stabilize_fct(c("a", "b", "c"), min_size = 5))
#> Error in eval(expr, envir) : 
#>   `c("a", "b", "c")` must have size >= 5.
#> ✖ 3 is too small.
try(stabilize_fct(c("a", "b", "c"), max_size = 2))
#> Error in eval(expr, envir) : 
#>   `c("a", "b", "c")` must have size <= 2.
#> ✖ 3 is too big.

stabilize_fct_scalar("a")
#> [1] a
#> Levels: a
try(stabilize_fct_scalar(letters))
#> Error in eval(expr, envir) : 
#>   `letters` must be a single <factor>.
#> ✖ `letters` has 26 values.
try(stabilize_fct_scalar("c", levels = c("a", "b")))
#> Error in eval(expr, envir) : 
#>   All values of `"c"` must be present in `levels` or `to_na`.
#> ℹ Disallowed values: c
#> ℹ Allowed values: a and b