Checks if x is a flag or NA (missing logical scalar).
check_flag_na(x, coerce = TRUE, x_name = substitute(x), error = TRUE)The object to check.
A flag indicating whether to drop attributes including names.
A string of the name of the object x.
A flag indicating whether to throw an informative error or immediately generate an informative message if the check fails.
An invisible copy of x (if it doesn't throw an error).
Useful when using flag to pass one of three options.