missing: Missing values

In hadley/rlang: Functions for Base Types and Core R and 'Tidyverse' Features

Missing values

Description

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

Format

An object of class logical of length 1.

An object of class integer of length 1.

An object of class numeric of length 1.

An object of class character of length 1.

An object of class complex of length 1.

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)
typeof(na_lgl)
typeof(na_int)

# 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)

hadley/rlang documentation built on Dec. 17, 2024, 3:26 a.m.