The R Project SVN R

\name{assign}
\alias{assign}
\alias{<-}
\alias{=}
\alias{<<-}
\alias{->}
\alias{->>}
\title{Assign a Value to a Name}
\description{
  Assign a value to a name in an environment.
}
\usage{
assign(x, value, pos = -1, envir = as.environment(pos),
       inherits = FALSE, immediate = TRUE)
x <- value
x <<- value
value -> x
value ->> x

x = value
}
\arguments{
  \item{x}{a variable name (given as a quoted string in the function call).}
  \item{value}{a value to be assigned to \code{x}.}
  \item{pos}{where to do the assignment.  By default, assigns into the
    current environment.  See the details for other possibilities.}
  \item{envir}{the \code{\link{environment}} to use. See the details section.}
  \item{inherits}{should the enclosing frames of the environment be
    inspected?}
  \item{immediate}{an ignored compatibility feature.}
}
\details{
  The \code{pos} argument can specify the  environment in which to assign
  the object in any of several ways:
  as an integer (the position in the \code{\link{search}} list); as
  the character string name of an element in the search list; or as an
  \code{\link{environment}} (including using \code{\link{sys.frame}} to
  access the currently active function calls).
  The \code{envir} argument is an alternative way to specify an
  environment, but is primarily there for back compatibility.

  \code{assign} does not dispatch assignment methods, so it cannot be
  used to set elements of vectors, names, attributes, etc.
}
\section{Assignment Operators}{
  There are three different assignment
  operators. The operators \code{<-} and \code{=} assign into the
  environment in which they are evaluated.  The \code{<-} can be used
  anywhere, but the \code{=} is only allowed at the top level (that
  is, in the complete expression typed by the user) or as one of the
  subexpressions in a braced list of expressions.

  
  The operators \code{<<-} and \code{->>} cause a search to made
  through the environment for an existing
  definition of the variable being assigned.  If such a variable is
  found then its value is redefined, otherwise assignment takes place
  globally. Note that their differs from that in
  the S language, but is useful in conjunction with the scoping rules of
  R.

  In all the assignment operator expressions, \code{x} can be a name
  or an expression defining a part of an object to be replaced (e.g.,
  \code{z[[1]]}).  The name does not need to be quoted, though it can
  be.
}
\value{
  This function is invoked for its side effect, which is assigning
  \code{value} to the variable \code{x}.  If no \code{envir} is
  specified, then the assignment takes place in the currently active
  environment.

  If \code{inherits} is \code{TRUE}, enclosing environments of the supplied
  environment are searched until the variable \code{x} is encountered.
  The value is then assigned in the environment in which the variable is
  encountered.  If the symbol is not encountered then assignment takes
  place in the user's workspace (the global environment).

  If \code{inherits} is \code{FALSE}, assignment takes place in the
  initial frame of \code{envir}.
}

\seealso{
  \code{\link{get}},
  \code{\link{exists}},
  \code{\link{environment}}.}
\examples{
for(i in 1:6) { #-- Create objects  'r1', 'r2', ... 'r6' --
 nam <- paste("r",i, sep=".")
 assign(nam, 1:i)
}
ls(pat="^r..$")

##-- Global assignment within a function:
myf <- function(x) {
 innerf <- function(x) assign("Global.res", x^2, env = .GlobalEnv)
 innerf(x+1)
}
myf(3)
Global.res # 16

a<-1:4
assign("a[1]",2)
a[1]==2          #FALSE
get("a[1]")==2   #TRUE

}
\keyword{data}