NULL                  package:base                  R Documentation

The Null Object

Description:

     'NULL' represents the null object in R: it is a reserved word.
     NULL is often returned by expressions and functions whose value is
     undefined: it is also used as the empty pairlist.

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

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

Usage:

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

Arguments:

       x: an object to be tested or coerced.

     ...: ignored.

References:

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

Examples:

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

