R: "Tagged" missing values

tagged_na {haven} | R Documentation

## "Tagged" missing values

### Description

"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.

### Usage

    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
    is.na(x)

    # To see that they're special, you need to use na_tag(),
    # is_tagged_na(), or print_tagged_na():
    is_tagged_na(x)
    na_tag(x)
    print_tagged_na(x)

    # You can test for specific tagged NAs with the second argument
    is_tagged_na(x, "a")

    # 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"))

[Package haven version 2.4.2 Index]