is_named: Is object named?

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

Is object named?

Description

• is_named() is a scalar predicate that checks that x has a names attribute and that none of the names are missing or empty (NA or "").

• is_named2() is like is_named() but always returns TRUE for empty vectors, even those that don't have a names attribute. In other words, it tests for the property that each element of a vector is named. is_named2() composes well with names2() whereas is_named() composes with names().

• have_name() is a vectorised variant.

Usage

is_named(x)

is_named2(x)

have_name(x)

Arguments

x	A vector to test.

Details

is_named() always returns TRUE for empty vectors because

Value

is_named() and is_named2() are scalar predicates that return TRUE or FALSE. have_name() is vectorised and returns a logical vector as long as the input.

Examples

# is_named() is a scalar predicate about the whole vector of names:
is_named(c(a = 1, b = 2))
is_named(c(a = 1, 2))

# Unlike is_named2(), is_named() returns `FALSE` for empty vectors
# that don't have a `names` attribute.
is_named(list())
is_named2(list())

# have_name() is a vectorised predicate
have_name(c(a = 1, b = 2))
have_name(c(a = 1, 2))

# Empty and missing names are treated as invalid:
invalid <- set_names(letters[1:5])
names(invalid)[1] <- ""
names(invalid)[3] <- NA

is_named(invalid)
have_name(invalid)

# A data frame normally has valid, unique names
is_named(mtcars)
have_name(mtcars)

# A matrix usually doesn't because the names are stored in a
# different attribute
mat <- matrix(1:4, 2)
colnames(mat) <- c("a", "b")
is_named(mat)
names(mat)

hadley/rlang documentation built on Nov. 1, 2024, 4 p.m.