"Tagged" missing values work exactly like regular R missing values except that they store one additional byte of information a tag, which is usually a letter ("a" to "z"). When by loading a SAS and Stata file, the tagged missing values always use lower case values.

tagged_na(...)

na_tag(x)

is_tagged_na(x, tag = NULL)

format_tagged_na(x, digits = getOption("digits"))

print_tagged_na(x, digits = getOption("digits"))

Arguments

...

Vectors containing single character. The letter will be used to "tag" the missing value.

x

A numeric vector

tag

If NULL, will only return true if the tag has this value.

digits

Number of digits to use in string representation

Details

format_tagged_na() and print_tagged_na() format tagged NA's as NA(a), NA(b), etc.

Examples

x <- c(1:5, tagged_na("a"), tagged_na("z"), NA) # Tagged NA's work identically to regular NAs x
#> [1] 1 2 3 4 5 NA NA NA
#> [1] FALSE FALSE FALSE FALSE FALSE TRUE TRUE TRUE
# To see that they're special, you need to use na_tag(), # is_tagged_na(), or print_tagged_na(): is_tagged_na(x)
#> [1] FALSE FALSE FALSE FALSE FALSE TRUE TRUE FALSE
na_tag(x)
#> [1] NA NA NA NA NA "a" "z" NA
print_tagged_na(x)
#> [1] 1 2 3 4 5 NA(a) NA(z) NA
# You can test for specific tagged NAs with the second argument is_tagged_na(x, "a")
#> [1] FALSE FALSE FALSE FALSE FALSE TRUE FALSE FALSE
# Because the support for tagged's NAs is somewhat tagged on to R, # the left-most NA will tend to be preserved in arithmetic operations. na_tag(tagged_na("a") + tagged_na("z"))
#> [1] "a"