NULL

From base v3.3 by R-core R-core@R-project.org

The Null Object

NULL represents the null object in R: it is a reserved word. NULL is often returned by expressions and functions whose value is undefined.

as.null ignores its argument and returns the value NULL.

is.null returns TRUE if its argument is NULL and FALSE otherwise.

Keywords: manip, attribute, list, sysdata

Usage

NULL
as.null(x, ...)
is.null(x)

Arguments

x: an object to be tested or coerced.
...: ignored.

Details

NULL can be indexed (see Extract) in just about any syntactically legal way: whether is makes sense or not, the result is always NULL. Objects with value NULL can be changed by replacement operators and will be coerced to the type of the right-hand side.

NULL is also used as the empty pairlist.

Note

is.null is a primitive function.

References

Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988) The New S Language. Wadsworth & Brooks/Cole.

Examples

library(base)

is.null(list())     # FALSE (on purpose!)
is.null(integer(0)) # FALSE
is.null(logical(0)) # FALSE
as.null(list(a = 1, b = "c"))

Documentation reproduced from package base, version 3.3, License: Part of R @VERSION@

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