Type:	Package
Title:	Clean and Simple Argument Checking
Version:	0.1.0
Description:	Checks function arguments, ideally for use in R packages. Uses a simple interface and produces clean, informative error messages using 'cli'.
Depends:	R (≥ 4.1.0)
Imports:	rlang (≥ 1.1.0), cli (≥ 3.6.4), stats, utils
License:	GPL-2 | GPL-3 [expanded from: GPL (≥ 2)]
Encoding:	UTF-8
URL:	https://ngreifer.github.io/arg/, https://github.com/ngreifer/arg
BugReports:	https://github.com/ngreifer/arg/issues
RoxygenNote:	7.3.3
NeedsCompilation:	no
Packaged:	2026-04-03 14:07:57 UTC; NoahGreifer
Author:	Noah Greifer [aut, cre]
Maintainer:	Noah Greifer <noah.greifer@gmail.com>
Repository:	CRAN
Date/Publication:	2026-04-09 15:20:02 UTC

arg: Clean and Simple Argument Checking

Description

Checks function arguments, ideally for use in R packages. Uses a simple interface and produces clean, informative error messages using 'cli'.

Author(s)

Maintainer: Noah Greifer noah.greifer@gmail.com (ORCID)

See Also

Useful links:

• https://ngreifer.github.io/arg/

• https://github.com/ngreifer/arg

• Report bugs at https://github.com/ngreifer/arg/issues

Check Values in Range

Description

Checks whether values are within a range (arg_between()), greater than some value (arg_gt()), greater than or equal to some value (arg_gte()), less than some value (arg_lt()), or less than or equal to some value (arg_lte()).

Usage

arg_between(
  x,
  range = c(0, 1),
  inclusive = TRUE,
  .arg = rlang::caller_arg(x),
  .msg = NULL,
  .call
)

arg_gt(x, bound = 0, .arg = rlang::caller_arg(x), .msg = NULL, .call)

arg_gte(x, bound = 0, .arg = rlang::caller_arg(x), .msg = NULL, .call)

arg_lt(x, bound = 0, .arg = rlang::caller_arg(x), .msg = NULL, .call)

arg_lte(x, bound = 0, .arg = rlang::caller_arg(x), .msg = NULL, .call)

Arguments

Details

x is not checked for type, as it is possible for values other than numeric values to be passed and compared; however, an error will be thrown if typeof(x) is not equal to typeof(range) or typeof(bound). NA values of x will be removed. The arguments to range, inclusive, and bound are checked for appropriateness.

Value

Returns NULL invisibly if an error is not thrown.

Examples

z <- 2

try(arg_between(z, c(1, 3))) # No error
try(arg_between(z, c(1, 2))) # No error
try(arg_between(z, c(1, 2),
                inclusive = FALSE)) # Error
try(arg_between(z, c(1, 2),
                inclusive = c(TRUE, FALSE))) # Error

try(arg_gt(z, 0))  # No error
try(arg_gt(z, 2))  # Error
try(arg_gte(z, 2)) # No error

try(arg_lt(z, 0))  # Error
try(arg_lt(z, 2))  # Error
try(arg_lte(z, 2)) # No error

try(arg_lte(z, "3")) # Error: wrong type

Check Character Argument

Description

Checks whether an argument is a character vector (arg_character()), a character scalar (arg_string()), or a factor (arg_factor()).

Usage

arg_character(x, .arg = rlang::caller_arg(x), .msg = NULL, .call)

arg_string(x, .arg = rlang::caller_arg(x), .msg = NULL, .call)

arg_factor(x, .arg = rlang::caller_arg(x), .msg = NULL, .call)

Arguments

Details

NA values in arg_string() will cause an error to be thrown.

Value

Returns NULL invisibly if an error is not thrown.

See Also

is.character(), is.factor(), rlang::is_string()

Examples

f <- function(z) {
  arg_string(z)
}

try(f("a")) # No error
try(f(c("a", "b"))) # Error: arg_string() requires scalar
try(f(NA)) # NAs not allowed for arg_string()

Check Common Argument Types

Description

Checks whether an argument is an atomic vector (arg_atomic()), a dimensionless atomic vector (arg_vector()), a list (arg_list()), a data frame (arg_data.frame()), a matrix (arg_matrix()), an array (arg_array()), a rectangular data set (arg_data()), or an environment (arg_env()).

Usage

arg_atomic(x, .arg = rlang::caller_arg(x), .msg = NULL, .call)

arg_vector(x, .arg = rlang::caller_arg(x), .msg = NULL, .call)

arg_list(x, df_ok = FALSE, .arg = rlang::caller_arg(x), .msg = NULL, .call)

arg_data.frame(x, .arg = rlang::caller_arg(x), .msg = NULL, .call)

arg_matrix(x, .arg = rlang::caller_arg(x), .msg = NULL, .call)

arg_array(x, .arg = rlang::caller_arg(x), .msg = NULL, .call)

arg_data(x, .arg = rlang::caller_arg(x), .msg = NULL, .call)

arg_env(x, .arg = rlang::caller_arg(x), .msg = NULL, .call)

Arguments

Details

Atomic vectors are checked using is.atomic(). Because matrices are considered atomic vectors, arg_vector() additionally checks that there is no "dims" attribute, i.e., that length(dim(x)) == 0L. arg_data() checks whether x is either a data frame or a matrix. arg_list() checks whether x is a list; when df = FALSE, it throws an error when x is a data frame, even though data frames are lists.

Value

Returns NULL invisibly if an error is not thrown.

See Also

is.atomic(), is.list(), is.data.frame(), is.matrix(), is.array(), is.environment(), arg_is()

Examples

vec <- 1:6
mat <- as.matrix(vec)
dat <- as.data.frame(mat)
lis <- as.list(vec)
nul <- NULL

# arg_atomic
try(arg_atomic(vec))
try(arg_atomic(mat))
try(arg_atomic(dat))
try(arg_atomic(lis))
try(arg_atomic(nul))

# arg_vector
try(arg_vector(vec))
try(arg_vector(mat))

# arg_matrix
try(arg_matrix(vec))
try(arg_matrix(mat))
try(arg_matrix(dat))

# arg_data.frame
try(arg_data.frame(vec))
try(arg_data.frame(mat))
try(arg_data.frame(dat))

# arg_data
try(arg_data(vec))
try(arg_data(mat))
try(arg_data(dat))

Check Supplied Dots Argument

Description

Checks whether an argument was supplied to ....

Usage

arg_dots_supplied(..., .msg = NULL, .call)

arg_dots_not_supplied(..., .msg = NULL, .call)

Arguments

Details

arg_dots_supplied() checks whether arguments were passed to the ... (i.e., "dots") argument of a function. These arguments are not evaluated. arg_dots_supplied() throws an error if ...length() is 0. It can be useful for when a function must have additional arguments. For example, arg_or() and when_supplied() use arg_dots_supplied().

arg_dots_not_supplied() checks whether no arguments were passed to ..., again without evaluating the arguments and using ...length(). It can be useful when a function appears to allow further arguments (e.g., because it is a method of a generic), but when the author does not want the user to supply them.

Value

Returns NULL invisibly if an error is not thrown.

See Also

arg_supplied()

Examples

f <- function(...) {
  arg_dots_supplied(...)
}

try(f(1)) # No error: argument supplied
try(f())  # Error!

Check Element

Description

Checks whether values in an argument are all elements of some set (arg_element()) or are not all elements of a set (arg_not_element()). arg_element() throws an error when all(is.element(x, values)) is FALSE, and arg_not_element() throws an error when any(is.element(x, values)) is TRUE.

Usage

arg_element(x, values, .arg = rlang::caller_arg(x), .msg = NULL, .call)

arg_not_element(x, values, .arg = rlang::caller_arg(x), .msg = NULL, .call)

Arguments

Details

arg_element() can be useful for checking whether an argument matches one or more allowed values. It's important that a check is done beforehand to ensure x is the correct type, e.g., using arg_string() or arg_character() if values is a character vector. No partial matching is used; the values must match exactly. Use match_arg() to allow partial matching and return the full version of the supplied argument.

arg_not_element() can be useful for ensuring there is no duplication of values between an argument and some other set.

Value

Returns NULL invisibly if an error is not thrown.

See Also

is.element(), match_arg()

Examples

f <- function(z) {
  arg_element(z, c("opt1", "opt2", "opt3"))
}

try(f("opt1"))            # No error
try(f(c("opt1", "opt2"))) # No error, all are elements
try(f(c("opt1", "opt1"))) # No error: repeats allowed
try(f("bad_arg"))         # Error: not an element of set
try(f("opt"))             # Error: partial matching not allowed
try(f(c("opt1", "bad_arg"))) # Error: one non-match

g <- function(z) {
  arg_not_element(z, c("bad1", "bad2", "bad3"))
}

try(g("bad1"))            # Error: z is an element
try(g(c("bad1", "opt2"))) # Error: at least one bad match
try(g("opt1"))            # No error: not an element
try(g(c("opt1", "opt2"))) # No error, none are elements

Check Equal Arguments

Description

Checks whether two arguments are equal (arg_equal()) or not equal (arg_not_equal()).

Usage

arg_equal(
  x,
  x2,
  ...,
  .arg = rlang::caller_arg(x),
  .arg2 = rlang::caller_arg(x2),
  .msg = NULL,
  .call
)

arg_not_equal(
  x,
  x2,
  ...,
  .arg = rlang::caller_arg(x),
  .arg2 = rlang::caller_arg(x2),
  .msg = NULL,
  .call
)

Arguments

Details

Tests for equality are performed by evaluating whether isTRUE(all.equal(x, x2, ...)) is TRUE or FALSE.

Value

Returns NULL invisibly if an error is not thrown.

See Also

all.equal()

Examples

f <- function(x, y, ...) {
  arg_equal(x, y, ...)
}

try(f(x = 1, y = 1))      ## No error
try(f(x = 1L, y = 1.0))   ## No error despite type difference
try(f(x = 1, y = 1.00001, ## No error, within tolerance
      tolerance = .001))

try(f(x = 1, y = 2))       ## Error: different
try(f(x = 1, y = 1.00001)) ## Error

g <- function(x, y, ...) {
  arg_not_equal(x, y, ...)
}

try(g(x = 1, y = 1)) ## Error
try(g(x = 1, y = 2)) ## No error

Check Formula Argument

Description

Checks whether an argument is a formula.

Usage

arg_formula(
  x,
  one_sided = NULL,
  .arg = rlang::caller_arg(x),
  .msg = NULL,
  .call
)

Arguments

Value

Returns NULL invisibly if an error is not thrown.

See Also

rlang::is_formula(), arg_is()

Examples

form1 <- ~a + b
form2 <- y ~ a + b
not_form <- 1:3

try(arg_formula(form1))    # No error
try(arg_formula(form2))    # No error
try(arg_formula(not_form)) # Error: not a formula

try(arg_formula(form1,
                one_sided = TRUE)) # No error
try(arg_formula(form2,
                one_sided = TRUE)) # Error, not one-sided

try(arg_formula(form1,
                one_sided = FALSE)) # Error, only one-sided
try(arg_formula(form2,
                one_sided = FALSE)) # No error

Check Function Argument

Description

Checks whether an argument is a function.

Usage

arg_function(x, .arg = rlang::caller_arg(x), .msg = NULL, .call)

Arguments

Value

Returns NULL invisibly if an error is not thrown.

See Also

rlang::is_function(), arg_is()

Examples

f <- function(z) {
  arg_function(z)
}

try(f(print))   # No error
try(f("print")) # Error: must be a function

Check Index Argument

Description

Checks whether an argument is a valid column index (arg_index()) of a data set or a vector thereof (arg_indices()).

Usage

arg_index(
  x,
  data,
  .arg = rlang::caller_arg(x),
  .arg_data = rlang::caller_arg(data),
  .msg = NULL,
  .call
)

arg_indices(
  x,
  data,
  .arg = rlang::caller_arg(x),
  .arg_data = rlang::caller_arg(data),
  .msg = NULL,
  .call
)

Arguments

Details

For arg_indices(), an error will be thrown unless one of the following are true:

• x is a vector of counts (see arg_counts()) less than or equal to ncol(data)

• x is a character vector with values a subset of colnames(data)

For arg_index(), x additionally must have length equal to 1. Passing arg_index() ensures that data[, x] (if data is a matrix) or data[[x]] (if x is a data frame) evaluate correctly.

If data has no column names, an error will be thrown if x is a character vector.

Value

Returns NULL invisibly if an error is not thrown.

See Also

arg_counts(), arg_character()

Examples

dat <- data.frame(col1 = 1:5,
                  col2 = 6:10)

f <- function(z) {
  arg_index(z, dat)
}

try(f(1))         # No error
try(f(3))         # Error: not a valid index
try(f("col1"))    # No error
try(f("bad_col")) # Error: not a valid index
try(f(1:2))       # Error: arg_index() requires scalar

mat <- matrix(1:9, ncol = 3)

g <- function(z) {
  arg_indices(z, mat)
}

try(g(1))     # No error
try(g(1:3))   # No error
try(g("col")) # Error: `mat` has no names

Check Argument Class

Description

Checks whether an argument is a of a specified class (arg_is()) or is not of a specified class (arg_is_not()).

Usage

arg_is(x, class, .arg = rlang::caller_arg(x), .msg = NULL, .call)

arg_is_not(x, class, .arg = rlang::caller_arg(x), .msg = NULL, .call)

Arguments

Details

arg_is() and arg_is_not() use inherits() to test for class membership. arg_is() throws an error only if no elements of class(x) are in class. arg_is_not() throws an error if any elements of class(x) are in class.

Sometimes this can be too permissive; combining arg_is() with arg_and() can be useful for requiring that an object is of multiple classes. Alternatively, combining arg_is_not() with arg_or() can be useful for requiring that an object is not a specific combination of classes. See Examples.

Value

Returns NULL invisibly if an error is not thrown.

See Also

inherits(), arg_or(); arg_data() for testing for specific kinds of objects (vectors, matrices, data frames, and lists)

Examples

obj <- structure(list(1),
                 class = "test")

try(arg_is(obj, "test"))            # No error
try(arg_is(obj, c("test", "quiz"))) # No error
try(arg_is(obj, "quiz"))            # Error

try(arg_is_not(obj, "test"))            # Error
try(arg_is_not(obj, c("test", "quiz"))) # Error
try(arg_is_not(obj, "quiz"))            # No error

# Multiple classes
obj2 <- structure(list(1),
                  class = c("test", "essay"))

try(arg_is(obj2, c("test", "quiz")))     # No error
try(arg_is_not(obj2, c("test", "quiz"))) # Error

## Require argument to be of multiple classes
try(arg_and(obj2,
            arg_is("test"),
            arg_is("quiz")))

## Require argument to not be a specific combination of
## multiple classes
try(arg_or(obj2,
           arg_is_not("test"),
           arg_is_not("essay")))

Check Argument Length

Description

Checks whether an argument has a specified length.

Usage

arg_length(x, len = 1L, .arg = rlang::caller_arg(x), .msg = NULL, .call)

Arguments

Details

len can contain multiple allowed counts; an error will be thrown only if length(x) is not equal to any value of len.

Value

Returns NULL invisibly if an error is not thrown.

See Also

length(), arg_non_null() to specifically test that an object's length is or is not 0.

Examples

obj <- 1:4

try(arg_length(obj, 1))
try(arg_length(obj, 4))
try(arg_length(obj, c(1, 4)))

# These test the same thing:
try(arg_length(obj, c(0:3)))
try(when_not_null(obj,
                  arg_length(1:3)))

Check Logical Argument

Description

Checks whether an argument is a logical vector (arg_logical()) or a logical scalar (arg_flag()), i.e., a single logical value. Logical values include TRUE and FALSE.

Usage

arg_logical(x, .arg = rlang::caller_arg(x), .msg = NULL, .call)

arg_flag(x, .arg = rlang::caller_arg(x), .msg = NULL, .call)

Arguments

Details

NA values in arg_flag() will cause an error to be thrown.

Value

Returns NULL invisibly if an error is not thrown.

See Also

is.logical(), rlang::is_bool()

Examples

obj <- TRUE

try(arg_flag(obj))    # No error
try(arg_logical(obj)) # No error

obj <- c(TRUE, FALSE)

try(arg_flag(obj))    # Error: must be a scalar
try(arg_logical(obj)) # No error

obj <- 1L

try(arg_flag(obj))    # Error must be logical
try(arg_logical(obj)) # Error must be logical

Check Named Argument

Description

Checks whether an argument has valid (non-NULL, non-empty, and non-NA) names.

Usage

arg_named(x, .arg = rlang::caller_arg(x), .msg = NULL, .call)

arg_colnamed(x, .arg = rlang::caller_arg(x), .msg = NULL, .call)

Arguments

Details

arg_named() works for vectors, lists, and data frames. To check whether a matrix has column names, use arg_colnamed() (which also works for data frames, but not vectors or lists).

Value

Returns NULL invisibly if an error is not thrown.

See Also

rlang::is_named(), names(), colnames(), arg_data()

Examples

obj <- c(1,
         B = 2,
         C = 3)

try(arg_named(obj)) # Error: one name is blank

names(obj)[1L] <- "A"
try(arg_named(obj)) # No error

obj2 <- unname(obj)
try(arg_named(obj2)) # Error: no names

# Matrix and data frame
mat <- matrix(1:6, ncol = 2L)
colnames(mat) <- c("A", "B")

try(arg_named(mat))    # Error: matrices are not named
try(arg_colnamed(mat)) # No error

dat <- as.data.frame(mat)
try(arg_named(dat))    # No error: data frames are named
try(arg_colnamed(dat)) # No error

colnames(mat) <- NULL
try(arg_colnamed(mat)) # Error: no colnames

Check NA in Argument

Description

Checks whether an argument does not contain any NA values (arg_no_NA()), contains only NA values (arg_all_NA()), or is a scalar NA (arg_is_NA()).

Usage

arg_no_NA(x, .arg = rlang::caller_arg(x), .msg = NULL, .call)

arg_is_NA(x, .arg = rlang::caller_arg(x), .msg = NULL, .call)

arg_all_NA(x, .arg = rlang::caller_arg(x), .msg = NULL, .call)

Arguments

Details

arg_no_NA() throws an error when anyNA(x) is 0. arg_all_NA() throws an error when all(is.na(x)) is not FALSE. arg_is_NA() throws an error when length(x) is not 1 or anyNA(x) is FALSE.

arg_no_NA() is useful for checking that a meaningful argument was supplied. arg_all_NA() and arg_is_NA() are primarily used for in arg_or() to denote that NA is an allowed argument.

Value

Returns NULL invisibly if an error is not thrown.

See Also

arg_non_null(), arg_supplied(), anyNA()

Examples

f <- function(x) {
  arg_no_NA(x)  ## x must not be NA
}

try(f(1))           ## No error
try(f(NA))          ## Error: x is NA
try(f(c(1, NA, 3))) ## Error: x contains NA

f2 <- function(y) {
  arg_all_NA(y) ## y must be NA
}

try(f2(NA))          ## No error
try(f2(c(NA, NA)))   ## No error
try(f2(1))           ## Error: y is not NA
try(f2(c(1, NA, 3))) ## Error: y is not all NA

Check NULL Argument

Description

Checks whether an argument is non-NULL (arg_non_null()) or is NULL (arg_null()). arg_non_null() throws an error when length(x) is 0. arg_null() throws an error when length(x) is not 0.

Usage

arg_non_null(x, .arg = rlang::caller_arg(x), .msg = NULL, .call)

arg_null(x, .arg = rlang::caller_arg(x), .msg = NULL, .call)

Arguments

Details

Here, NULL refers to any length-0 object, including NULL, logical(0L), list(), 3[FALSE], etc. arg_non_null() is useful for checking that a meaningful argument was supplied. arg_null() is primarily used for in arg_or() to denote that NULL is an allowed argument.

Value

Returns NULL invisibly if an error is not thrown.

See Also

arg_length(), arg_no_NA(), arg_supplied()

Examples

f <- function(x = NULL, y = NULL) {
  arg_non_null(x) ## x must not be NULL
  arg_null(y)     ## y must be NULL
}

try(f(x = 1,    y = NULL)) ## No error
try(f(x = NULL, y = NULL)) ## Error: x is NULL
try(f(x = 1,    y = 1))    ## Error: y is non-NULL

# Any object of length 0 is considered NULL
try(f(x = numeric())) ## Error: x is NULL
try(f(x = list()))    ## Error: x is NULL

test <- c(1, 2)[c(FALSE, FALSE)]
try(f(x = test))      ## Error: x is NULL

# arg_null() is best used in and_or():
f2 <- function(z) {
  arg_or(z,
         arg_null(),
         arg_number())
}

try(f2(NULL)) ## No error; z can be NULL
try(f2(1))    ## No error; z can be a number
try(f2(TRUE)) ## Error: z must be NULL or a number

Check Numeric Argument

Description

Checks whether an argument is numeric, with some additional constraints if desired. arg_numeric() simply checks whether the argument is numeric. arg_number() checks whether the argument is a numeric scalar (i.e., a single number). arg_whole_numeric() and arg_whole_number() check whether the argument is a whole numeric vector or scalar, respectively. arg_counts() and arg_count() check whether the argument is a non-negative whole numeric vector or scalar, respectively.

Usage

arg_numeric(x, .arg = rlang::caller_arg(x), .msg = NULL, .call)

arg_number(x, .arg = rlang::caller_arg(x), .msg = NULL, .call)

arg_whole_numeric(x, .arg = rlang::caller_arg(x), .msg = NULL, .call)

arg_whole_number(x, .arg = rlang::caller_arg(x), .msg = NULL, .call)

arg_counts(x, .arg = rlang::caller_arg(x), .msg = NULL, .call)

arg_count(x, .arg = rlang::caller_arg(x), .msg = NULL, .call)

Arguments

Details

A whole number is decided by testing whether the value is an integer (i.e., using is.integer()) or if abs(x - trunc(x)) < sqrt(.Machine$double.eps). This is the same tolerance used by all.equal() to compare values.

Value

Returns NULL invisibly if an error is not thrown.

See Also

is.integer(), rlang::is_integerish()

Examples

count <- 3
whole <- -4
num <- .943

try(arg_number(count))       # No error
try(arg_whole_number(count)) # No error
try(arg_count(count))        # No error

try(arg_number(whole))       # No error
try(arg_whole_number(whole)) # No error
try(arg_count(whole))        # Error: negatives not allowed

try(arg_number(num))       # No error
try(arg_whole_number(num)) # Error: not a whole number
try(arg_count(num))        # Error: not a count

nums <- c(0, .5, 1)

try(arg_number(nums))  # Error: not a single number
try(arg_numeric(nums)) # No error
try(arg_counts(nums))  # Error: not counts

Check That Arguments Meet Some or All Criteria

Description

arg_or() checks whether an argument meets at least one given criterion. arg_and() checks whether an argument meets all given criteria.

Usage

arg_or(x, ..., .arg = rlang::caller_arg(x), .msg = NULL, .call)

arg_and(x, ..., .arg = rlang::caller_arg(x), .msg = NULL, .call)

Arguments

Details

For arg_or(), an error will be thrown only if x fails all of the supplied checks. This can be useful when an argument can take on one of several input types. For arg_and(), and error will be thrown if x fails any of the supplied checks. This is less useful on its own, as the checks can simply occur in sequence without arg_and(), but arg_and() can be supplied to the ... argument of arg_or() to create more complicated criteria.

The ... arguments can be passed either as functions, e.g.,

arg_or(x,
       arg_number,
       arg_string,
       arg_flag)

or as unevaluated function calls with the x argument absent, e.g.,

arg_or(x,
       arg_number(),
       arg_string(),
       arg_flag())

or as a mixture of both.

These functions do their best to provide a clean error message composed of all the error messages for the failed checks. With many options, this can yield a complicated error message, so use caution. arg_and() marks with a check (v) any passed checks and with a cross (x) any failed checks.

Value

Returns NULL invisibly if an error is not thrown.

See Also

arg_supplied(), when_not_null()

Examples

# `arg_or()`
f <- function(z) {
  arg_or(z,
         arg_number,
         arg_string,
         arg_flag)
}

try(f(1))      # No error
try(f("test")) # No error
try(f(TRUE))   # No error
try(f(1:4))    # Error: neither a number, string,
#              #        or flag, but a vector

# `arg_and()`
g <- function(z) {
  arg_and(z,
          arg_counts,
          arg_length(len = 2),
          arg_lt(bound = 5))
}

try(g(c(1, 2)))     # No error
try(g(c(1, 7)))     # Error: not < 5
try(g(c(1.1, 2.1))) # Error: not counts
try(g(4))           # Error: not length 2
try(g("bad"))       # Error: no criteria satisfied

# Chaining together `arg_and()` and `arg_or()`
h <- function(z) {
  arg_or(z,
         arg_all_NA,
         arg_and(arg_count,
                 arg_lt(5)),
         arg_and(arg_string,
                 arg_element(c("a", "b", "c"))))
}

try(h(NA))  # No error
try(h(1))   # No error
try(h("a")) # No error
try(h(7))   # Error: not < 5
try(h("d")) # Error: not in "a", "b", or "c"

Check Supplied Argument

Description

Checks whether an argument with no default value was supplied. An error will be thrown if rlang::is_missing(x) is TRUE, i.e., if an argument with no default is omitted from a function call.

Usage

arg_supplied(x, .arg = rlang::caller_arg(x), .msg = NULL, .call)

Arguments

Value

Returns NULL invisibly if an error is not thrown.

See Also

arg_non_null(), arg_no_NA(), rlang::is_missing(), rlang::check_required()

Examples

f <- function(z) {
  arg_supplied(z)
}

try(f(1)) ## No error: argument supplied
try(f())  ## Error!

# Will not throw for NULL or default arguments
try(f(NULL)) ## No error: argument supplied

f2 <- function(z = NULL) {
  arg_supplied(z)
}

try(f2()) ## No error; default provided

Check Symmetric Matrix Argument

Description

arg_symmetric() checks whether an argument is a square, symmetric, numeric matrix. arg_cov() checks whether an argument is like a covariance matrix (i.e., square and symmetric with non-negative diagonal entries). arg_cor() checks whether an argument is like a correlation matrix (i.e., square and symmetric with all values between -1 and 1 and ones on the diagonal). arg_distance() checks whether an argument is like a distance matrix (i.e., square and symmetric with non-negative entries and zeros on the diagonal).

Usage

arg_symmetric(
  x,
  tol = 100 * .Machine$double.eps,
  ...,
  .arg = rlang::caller_arg(x),
  .msg = NULL,
  .call
)

arg_cov(
  x,
  tol = 100 * .Machine$double.eps,
  ...,
  .arg = rlang::caller_arg(x),
  .msg = NULL,
  .call
)

arg_cor(
  x,
  tol = 100 * .Machine$double.eps,
  ...,
  .arg = rlang::caller_arg(x),
  .msg = NULL,
  .call
)

arg_distance(
  x,
  tol = 100 * .Machine$double.eps,
  ...,
  .arg = rlang::caller_arg(x),
  .msg = NULL,
  .call
)

Arguments

Details

These functions check that an argument is a square, symmetric, numeric matrix. This can be useful when a function can accept a covariance matrix, correlation matrix, or distance matrix. arg_cov() will throw an error if any values on its diagonal are less than -tol. arg_cor() will throw an error if any of its values are greater than 1 + tol in absolute value or if the diagonal entries are not between -1 - tol and 1 + tol. arg_distance() will thrown an error if any of its values are less than -tol or if the diagonal entries are not between -tol and tol. The tolerance is just slightly greater than 0 to allow for numeric imprecision.

No checks on semi-definiteness or rank are performed.

Value

Returns NULL invisibly if an error is not thrown.

See Also

arg_numeric(), arg_matrix(), arg_between(), isSymmetric()

Examples

set.seed(1234)
mat <- matrix(rnorm(12), ncol = 3L) # Non square
sym_mat <- -crossprod(mat)          # Square, symmetric
cov_mat <- cov(mat)                 # Covariance
cor_mat <- cor(mat)                 # Correlation
dist_mat <- as.matrix(dist(mat))    # Distance

try(arg_symmetric(mat))     # Error: not square
try(arg_symmetric(sym_mat)) # No error

try(arg_cov(sym_mat)) # Error: diagonal must be non-negative
try(arg_cov(cov_mat)) # No error

try(arg_cor(cov_mat)) # Error: values must be in [-1, 1]
try(arg_cor(cor_mat)) # No error

try(arg_distance(cor_mat))  # Error: diagonal must be 0
try(arg_distance(dist_mat)) # No error

Check Unique Argument

Description

Checks whether an argument contains only unique values.

Usage

arg_unique(x, ..., .arg = rlang::caller_arg(x), .msg = NULL, .call)

Arguments

Value

Returns NULL invisibly if an error is not thrown.

See Also

anyDuplicated()

Examples

f <- function(z) {
  arg_unique(z)
}

try(f(1:3))     # No error
try(f(NULL))    # No error for NULL
try(f(c(1, 1))) # Error: repeated values

Throw an Error, Warning, or Message

Description

These functions are similar to stop()/cli::cli_abort(), warning()/cli::cli_warn(), and message()/cli::cli_inform(), throwing an error, warning, and message, respectively. Minor processing is done to capitalize the first letter of the message, add a period at the end (if it makes sense to), and add information about the calling function.

Usage

err(m, .call, .envir = rlang::caller_env())

wrn(m, immediate = TRUE, .envir = rlang::caller_env())

msg(m, .envir = rlang::caller_env())

Arguments

Details

These functions are simple wrappers for the corresponding functions in rlang, namely rlang::abort() for err(), rlang::warn() for wrn(), and rlang::inform() for msg(), but which function almost identically to the cli versions. Their main differences are that they additionally process the input (capitalizing the first character of the message and adding a period to the end if needed, unless multiple strings are provided). err() is used inside all ⁠arg_*()⁠ functions in arg.

Value

err() throws an error condition. wrn() throws a warning condition and invisibly returns the formatted warning message as a string. msg() signals a message and invisibly returns NULL.

See Also

• Base versions: stop(), warning(), message()

• rlang versions: rlang::abort(), rlang::warn(), rlang::inform()

• cli versions: cli::cli_abort(), cli::cli_warn(), cli::cli_inform()

Examples

f <- function(x) {
  err("this is an error, and {.arg x} is {.type {x}}")
}

try(f(1))

g <- function(x) {
  wrn("this warning displayed last", immediate = FALSE)
  wrn("this warning displayed first")
}

try(g(1))

h <- function() {
  msg("is a period added at the end?")
  msg("not when the message ends in punctuation!")
  msg(c("or when multiple",
        "!" = "messages",
        "v" = "are",
        "*" = "displayed"))
  msg("otherwise yes")
}

h()

Argument Verification

Description

An alternative to match.arg() with improved error messages via cli. Returns the first choice if x is NULL, and supports partial matching.

Usage

match_arg(
  x,
  choices,
  several.ok = FALSE,
  ignore.case = TRUE,
  .context = NULL,
  .arg = rlang::caller_arg(x),
  .call
)

Arguments

Details

Partial matching is supported via pmatch(). If no match is found, an error is thrown listing the valid choices.

Checks are run on x prior to matching: first, arg_supplied() is used to check whether x was supplied; then arg_string() (if several.ok = TRUE) or arg_character() (if several.ok = FALSE) is used to check whether x is a valid string or character vector, respectively.

When ignore.case = TRUE (the default), an initial case-sensitive match is run, and if any values in x are unmatched, a second, case-insensitive match is run. When ignore.case = FALSE, only the first match is run. This ensures that exact matches (on both content and case) are prioritized before case-insensitive matches.

Value

A character string (or vector, if several.ok = TRUE) of the matched element(s) from choices. If there is no match, an error is thrown. When several.ok = TRUE, no error is thrown if there is at least one match.

See Also

• match.arg() for the base R version

• pmatch() for the function implementing partial string matching

• arg_element() for a version without type checking and that doesn't support partial matching

• rlang::arg_match() for a similar rlang function that doesn't support partial matching.

Examples

f <- function(z = NULL) {
  match_arg(z, c("None", "Exact", "Partial"),
            ignore.case = TRUE)
}

try(f())            # "None" (first choice returned)
try(f("partial"))   # "Partial"
try(f("p"))         # "Partial" (partial match)
try(f(c("e", "p"))) # Error: several.ok = FALSE

# several.ok = TRUE
g <- function(z = NULL) {
  match_arg(z, c("None", "Exact", "Partial"),
            several.ok = TRUE)
}

try(g("exact"))               # Error: case not ignored
try(g("Exact"))               # "Exact"
try(g(c("Exact", "Partial"))) # "Exact", "Partial"
try(g(c("Exact", "Wrong")))   # "Exact"
try(g(c("Wrong1", "Wrong2"))) # Error: no match

h <- function(z = NULL) {
  match_arg(z, c("None", "Exact", "Partial"),
            .context = "in {.fun h},")
}

try(h("Wrong")) # Error with context

Check Arguments When Supplied

Description

These functions check arguments only when they are supplied (when_supplied()) or when not NULL (when_not_null()). Multiple checks can be applied in sequence. This allows arguments not to have to be supplied, but checks them only if they are.

Usage

when_supplied(x, ..., .arg = rlang::caller_arg(x), .call)

when_not_null(x, ..., .arg = rlang::caller_arg(x), .call)

Arguments

Details

An error will be thrown only if x is supplied and fails one of the supplied checks (when_supplied()) or is not NULL and fails one of the supplied checks (when_not_null()).

The ... arguments can be passed either as functions, e.g.,

when_supplied(x,
              arg_number,
              arg_gt)

or as unevaluated function calls with the x argument absent, e.g.,

when_supplied(x,
              arg_number(),
              arg_gt(bound = 0))

or as a mixture of both.

when_supplied() only makes sense to use for an argument that has no default value but which can be omitted. when_not_null() makes sense to use for an argument with a default value of NULL.

Value

Returns NULL invisibly if an error is not thrown.

See Also

arg_or(), arg_supplied()

Examples

f <- function(z) {
  when_supplied(z,
                arg_number,
                arg_between(c(0, 1)))
}

try(f())    # No error: not supplied
try(f("a")) # Error: not a number
try(f(2))   # Error: not within 0-1 range
try(f(.7))  # No error: number within range

g <- function(z = NULL) {
  when_not_null(z,
                arg_number,
                arg_between(c(0, 1)))
}

try(g())     # No error: NULL okay
try(g(NULL)) # No error: NULL okay
try(g("a"))  # Error: not a number
try(g(2))    # Error: not within 0-1 range
try(g(.7))   # No error: number within range