The R Project SVN R

% File src/library/base/man/integer.Rd

% Part of the R package, https://www.R-project.org

% Copyright 1995-2010 R Core Team

% Distributed under GPL 2 or later

\name{integer}

\alias{integer}

\alias{as.integer}

\alias{is.integer}

\title{Integer Vectors}

\description{

  Creates or tests for objects of type \code{"integer"}.

}

\usage{

integer(length = 0)

as.integer(x, \dots)

is.integer(x)

}

\arguments{

  \item{length}{a non-negative integer specifying the desired length.

    Double values will be coerced to integer:

    supplying an argument of length other than one is an error.}

  \item{x}{object to be coerced or tested.}

  \item{\dots}{further arguments passed to or from other methods.}

}

\details{

  Integer vectors exist so that data can be passed to C or Fortran code

  which expects them, and so that (small) integer data can be represented

  exactly and compactly.

  Note that current implementations of \R use 32-bit integers for

  integer vectors, so the range of representable integers is restricted

  to about \eqn{\pm 2 \times 10^9}{+/-2*10^9}: \code{\link{double}}s can

  hold much larger integers exactly.

}

\value{

  \code{integer} creates a integer vector of the specified length.

  Each element of the vector is equal to \code{0}.

  \code{as.integer} attempts to coerce its argument to be of integer

  type.  The answer will be \code{NA} unless the coercion succeeds.  Real

  values larger in modulus than the largest integer are coerced to

  \code{NA} (unlike S which gives the most extreme integer of the same

  sign).  Non-integral numeric values are truncated towards zero (i.e.,

  \code{as.integer(x)} equals \code{\link{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

  \samp{0x} or \samp{0X}) can be converted, as well as any allowed by

  the platform for real numbers.  Like \code{\link{as.vector}} it strips

  attributes including names.  (To ensure that an object \code{x} is of

  integer type without stripping attributes, use

  \code{\link{storage.mode}(x) <- "integer"}.)

  \code{is.integer} returns \code{TRUE} or \code{FALSE} depending on

  whether its argument is of integer \link{type} or not, unless it is a

  factor when it returns \code{FALSE}.

}

\note{

  \code{is.integer(x)} does \bold{not} test if \code{x} contains integer

  numbers!  For that, use \code{\link{round}}, as in the function

  \code{is.wholenumber(x)} in the examples.

}

\references{

  \bibshow{R:Becker+Chambers+Wilks:1988}

}

\seealso{

  \code{\link{numeric}}, \code{\link{storage.mode}}.

  \code{\link{round}} (and \code{ceiling} and \code{floor} on that help

  page) to convert to integral values.

}

\examples{

## as.integer() truncates:

x <- pi * c(-1:1, 10)

as.integer(x)

is.integer(1) # is FALSE !

is.wholenumber <-

    function(x, tol = .Machine$double.eps^0.5)  abs(x - round(x)) < tol

is.wholenumber(1) # is TRUE

(x <- seq(1, 5, by = 0.5) )

is.wholenumber( x ) #-->  TRUE FALSE TRUE ...

}

\keyword{classes}