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

These are generic: you can write methods to handle specific classes of objects, see InternalMethods. The description here applies only to the default method.

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

Most types of language objects are regarded as recursive: those which are not are the atomic vector types, NULL and symbols (as given by as.name).

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

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 ??
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 (not in 0.62.3!)