"Tagged" missing values

Source: R/tagged_na.R

"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
is.na(x)

#> [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"