Validate a Character String

Checks that an argument is a single non-missing character string. Meant for the labelling arguments across the suite - dataName, captions, axis titles - where a vector or an NA would otherwise travel unnoticed into printed output.

Usage

checkString(x, name = deparse(substitute(x)))

Arguments

x

the value to check.

name

the argument name to use in the message. Defaults to the expression that was passed.

Value

x, invisibly.

Details

An optional argument that may also be NULL is guarded by the caller, if (!is.null(dataName)) checkString(dataName), rather than by a further argument here: whether the absence of a label is admissible is a decision of the function, not of the check.

The empty string is accepted. It is a legitimate label, and a caller that needs a non-empty one says so itself.

See also

checkConfLevel(), checkFlag(), checkCount()

Examples

dataName <- "smoking by sex"
checkString(dataName)

# all of these are rejected:
try(checkString(NA_character_))  # a missing label is not a label
#> Error : 'NA_character_' must be a single non-missing character string
try(checkString(c("a", "b")))    # length
#> Error : 'c("a", "b")' must be a single non-missing character string
try(checkString(42))             # type
#> Error : '42' must be a single non-missing character string