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% File src/library/base/man/integer.Rd
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% Part of the R package, https://www.R-project.org
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% Copyright 1995-2010 R Core Team
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% Distributed under GPL 2 or later
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\name{integer}
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\alias{integer}
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\alias{as.integer}
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\alias{is.integer}
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\title{Integer Vectors}
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\description{
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  Creates or tests for objects of type \code{"integer"}.
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}
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\usage{
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integer(length = 0)
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as.integer(x, \dots)
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is.integer(x)
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}
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\arguments{
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  \item{length}{A non-negative integer specifying the desired length.
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    Double values will be coerced to integer:
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    supplying an argument of length other than one is an error.}
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  \item{x}{object to be coerced or tested.}
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  \item{\dots}{further arguments passed to or from other methods.}
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}
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\details{
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  Integer vectors exist so that data can be passed to C or Fortran code
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  which expects them, and so that (small) integer data can be represented
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  exactly and compactly.
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  Note that current implementations of \R use 32-bit integers for
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  integer vectors, so the range of representable integers is restricted
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  to about \eqn{\pm 2 \times 10^9}{+/-2*10^9}: \code{\link{double}}s can
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  hold much larger integers exactly.
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}
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\value{
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  \code{integer} creates a integer vector of the specified length.
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  Each element of the vector is equal to \code{0}.
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  \code{as.integer} attempts to coerce its argument to be of integer
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  type.  The answer will be \code{NA} unless the coercion succeeds.  Real
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  values larger in modulus than the largest integer are coerced to
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  \code{NA} (unlike S which gives the most extreme integer of the same
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  sign).  Non-integral numeric values are truncated towards zero (i.e.,
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  \code{as.integer(x)} equals \code{\link{trunc}(x)} there), and
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  imaginary parts of complex numbers are discarded (with a warning).
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  Character strings containing optional whitespace followed by either a
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  decimal representation or a hexadecimal representation (starting with
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  \code{0x} or \code{0X}) can be converted, as well as any allowed by
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  the platform for real numbers.  Like \code{\link{as.vector}} it strips
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  attributes including names.  (To ensure that an object \code{x} is of
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  integer type without stripping attributes, use
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  \code{\link{storage.mode}(x) <- "integer"}.)
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  \code{is.integer} returns \code{TRUE} or \code{FALSE} depending on
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  whether its argument is of integer \link{type} or not, unless it is a
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  factor when it returns \code{FALSE}.
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}
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\note{
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  \code{is.integer(x)} does \bold{not} test if \code{x} contains integer
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  numbers!  For that, use \code{\link{round}}, as in the function
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  \code{is.wholenumber(x)} in the examples.
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}
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\references{
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  Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988)
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  \emph{The New S Language}.
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  Wadsworth & Brooks/Cole.
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}
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\seealso{
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  \code{\link{numeric}}, \code{\link{storage.mode}}.
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  \code{\link{round}} (and \code{ceiling} and \code{floor} on that help
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  page) to convert to integral values.
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}
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\examples{
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## as.integer() truncates:
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x <- pi * c(-1:1, 10)
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as.integer(x)
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is.integer(1) # is FALSE !
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is.wholenumber <-
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    function(x, tol = .Machine$double.eps^0.5)  abs(x - round(x)) < tol
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is.wholenumber(1) # is TRUE
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(x <- seq(1, 5, by = 0.5) )
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is.wholenumber( x ) #-->  TRUE FALSE TRUE ...
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}
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\keyword{classes}