na_if: Convert values to 'NA'

In dplyr: A Grammar of Data Manipulation

Convert values to NA

Description

This is a translation of the SQL command NULLIF. It is useful if you want to convert an annoying value to NA.

Usage

na_if(x, y)

Arguments

x	Vector to modify
y	Value or vector to compare against. When x and y are equal, the value in x will be replaced with NA. y is cast to the type of x before comparison. y is recycled to the size of x before comparison. This means that y can be a vector with the same size as x, but most of the time this will be a single value.

Value

A modified version of x that replaces any values that are equal to y with NA.

See Also

• coalesce() to replace NAs with the first non-missing value.

• replace_values() for making arbitrary replacements by value.

• replace_when() for making arbitrary replacements using logical conditions.

Examples

# `na_if()` is useful for replacing a single problematic value with `NA`
na_if(c(-99, 1, 4, 3, -99, 5), -99)
na_if(c("abc", "def", "", "ghi"), "")

# You can use it to standardize `NaN`s to `NA`
na_if(c(1, NaN, NA, 2, NaN), NaN)

# Because `na_if()` is an R translation of SQL's `NULLIF` command,
# it compares `x` and `y` element by element. Where `x` and `y` are
# equal, the value in `x` is replaced with an `NA`.
na_if(
  x = c(1, 2, 5, 5, 6),
  y = c(0, 2, 3, 5, 4)
)

# If you have multiple problematic values that you'd like to replace with
# `NA`, then `replace_values()` is a better choice than `na_if()`
x <- c(-99, 1, 4, 0, -99, 5, -1, 0, 5)
replace_values(x, c(0, -1, -99) ~ NA)

# You'd have to nest `na_if()`s to achieve this
try(na_if(x, c(0, -1, -99)))
na_if(na_if(na_if(x, 0), -1), -99)

# If you'd like to replace values that match a logical condition with `NA`,
# use `replace_when()`
replace_when(x, x < 0 ~ NA)

# If you'd like to replace `NA` with some other value, use `replace_values()`
x <- c(NA, 5, 2, NA, 0, 3)
replace_values(x, NA ~ 0)

# `na_if()` is particularly useful inside `mutate()`
starwars |>
  select(name, eye_color) |>
  mutate(eye_color = na_if(eye_color, "unknown"))

# `na_if()` can also be used with `mutate()` and `across()`
# to alter multiple columns
starwars |>
   mutate(across(where(is.character), ~na_if(., "unknown")))

dplyr documentation built on Feb. 3, 2026, 9:08 a.m.