Is an Object Atomic or Recursive?

Description

is.atomic returns TRUE if x is an atomic vector (or NULL) and FALSE otherwise.

is.recursive returns TRUE if x has a recursive (list-like) structure and FALSE otherwise.

Usage

is.atomic(x)
is.recursive(x)

Arguments

Details

is.atomic is true for the atomic vector types ("logical", "integer", "numeric", "complex", "character" and "raw") and NULL.

Most types of objects are regarded as recursive, except for atomic vector types, NULL and symbols (as given by as.name).

These are primitive functions.

References

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

See Also

is.list, is.language, etc, and the demo("is.things").

Examples

require(stats)

is.a.r <- function(x) c(is.atomic(x), is.recursive(x))

is.a.r(c(a=1,b=3))      # TRUE FALSE
is.a.r(list())          # FALSE TRUE - a list is a list
is.a.r(list(2))         # FALSE TRUE
is.a.r(lm)              # FALSE TRUE
is.a.r(y ~ x)           # FALSE TRUE
is.a.r(expression(x+1)) # FALSE TRUE (nowadays)