`integer`

creates a integer vector of the specified length.
Each element of the vector is equal to `0`

.

`as.integer`

attempts to coerce its argument to be of integer
type. The answer will be `NA`

unless the coercion succeeds. Real
values larger in modulus than the largest integer are coerced to
`NA`

(unlike S which gives the most extreme integer of the same
sign). Non-integral numeric values are truncated towards zero (i.e.,
`as.integer(x)`

equals `trunc(x)`

there), and
imaginary parts of complex numbers are discarded (with a warning).
Character strings containing optional whitespace followed by either a
decimal representation or a hexadecimal representation (starting with
`0x`

or `0X`

) can be converted, as well as any allowed by
the platform for real numbers. Like `as.vector`

it strips
attributes including names. (To ensure that an object `x`

is of
integer type without stripping attributes, use
`storage.mode(x) <- "integer"`

.)

`is.integer`

returns `TRUE`

or `FALSE`

depending on
whether its argument is of integer type or not, unless it is a
factor when it returns `FALSE`

.