is.recursive {base} | R Documentation

## 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

`x` | object to be tested.

### 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!)

[Package base version 2.3.1 Index]