Missing values — missing • rlang

Missing values are represented in R with the general symbol NA. They can be inserted in almost all data containers: all atomic vectors except raw vectors can contain missing values. To achieve this, R automatically converts the general NA symbol to a typed missing value appropriate for the target vector. The objects provided here are aliases for those typed NA objects.

Usage

na_lgl

na_int

na_dbl

na_chr

na_cpl

Details

Typed missing values are necessary because R needs sentinel values of the same type (i.e. the same machine representation of the data) as the containers into which they are inserted. The official typed missing values are NA_integer_, NA_real_, NA_character_ and NA_complex_. The missing value for logical vectors is simply the default NA. The aliases provided in rlang are consistently named and thus simpler to remember. Also, na_lgl is provided as an alias to NA that makes intent clearer.

Since na_lgl is the default NA, expressions such as c(NA, NA) yield logical vectors as no data is available to give a clue of the target type. In the same way, since lists and environments can contain any types, expressions like list(NA) store a logical NA.

Life cycle

These shortcuts might be moved to the vctrs package at some point. This is why they are marked as questioning.

Examples

typeof(NA)
#> [1] "logical"
typeof(na_lgl)
#> [1] "logical"
typeof(na_int)
#> [1] "integer"

# Note that while the base R missing symbols cannot be overwritten,
# that's not the case for rlang's aliases:
na_dbl <- NA
typeof(na_dbl)
#> [1] "logical"