Extract the only distinct value from a vector

Extracts the only distinct value from an atomic vector or throws an informative error if no values or multiple distinct values.

Usage

only(x, na_rm = FALSE)

Arguments

x

An atomic vector.

na_rm

A flag indicating whether to exclude missing values.

Value

The only distinct value from a vector otherwise throws an error.

Details

only() is useful when summarizing a vector by group while checking the assumption that it is constant within the group.

See also

dplyr::first()

Examples

only(c(1, 1))
#> [1] 1
only(c(NA, NA))
#> [1] NA
only(c(1, 1, NA), na_rm = TRUE)
#> [1] 1
try(only(character(0)))
#> Error in only(character(0)) : `x` must have at least 1 element.
try(only(c(1, NA)))
#> Error in only(c(1, NA)) : `x` must only have 1 distinct value.
try(only(c(1, 2)))
#> Error in only(c(1, 2)) : `x` must only have 1 distinct value.