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% Generated by roxygen2: do not edit by hand
% Please edit documentation in R/attrutil.R
\name{getsetattr}
\alias{getsetattr}
\alias{setattr}
\alias{setattributes}
\title{Attribute setting by reference}
\usage{
getsetattr(x, which, value)
setattr(x, which, value)
setattributes(x, attributes)
}
\arguments{
\item{x}{an R object}
\item{which}{name of the attribute}
\item{value}{value of the attribute, use NULL to remove this attribute}
\item{attributes}{a named list of attribute values}
}
\value{
invisible(), we do not return the changed object to remind you of
the fact that this function is called for its side-effect of changing its
input object.
}
\description{
Function \code{setattr} sets a singe attribute and function
\code{setattributes} sets a list of attributes.
}
\details{
The attributes of 'x' are changed in place without copying x. function
\code{setattributes} does only change the named attributes, it does not
delete the non-names attributes like \code{\link{attributes}} does.
}
\section{Functions}{
\itemize{
\item \code{setattr}:
\item \code{setattributes}:
}}
\examples{
x <- as.single(runif(10))
attr(x, "Csingle")
f <- function(x)attr(x, "Csingle") <- NULL
g <- function(x)setattr(x, "Csingle", NULL)
f(x)
x
g(x)
x
\dontrun{
# restart R
library(bit)
mysingle <- function(length = 0){
ret <- double(length)
setattr(ret, "Csingle", TRUE)
ret
}
# show that mysinge gives exactly the same result as single
identical(single(10), mysingle(10))
# look at the speedup and memory-savings of mysingle compared to single
system.time(mysingle(1e7))
memory.size(max=TRUE)
system.time(single(1e7))
memory.size(max=TRUE)
# look at the memory limits
# on my win32 machine the first line fails beause of not enough RAM, the second works
x <- single(1e8)
x <- mysingle(1e8)
# .g. performance with factors
x <- rep(factor(letters), length.out=1e7)
x[1:10]
# look how fast one can do this
system.time(setattr(x, "levels", rev(letters)))
x[1:10]
# look at the performance loss in time caused by the non-needed copying
system.time(levels(x) <- letters)
x[1:10]
# restart R
library(bit)
simplefactor <- function(n){
factor(rep(1:2, length.out=n))
}
mysimplefactor <- function(n){
ret <- rep(1:2, length.out=n)
setattr(ret, "levels", as.character(1:2))
setattr(ret, "class", "factor")
ret
}
identical(simplefactor(10), mysimplefactor(10))
system.time(x <- mysimplefactor(1e7))
memory.size(max=TRUE)
system.time(setattr(x, "levels", c("a","b")))
memory.size(max=TRUE)
x[1:4]
memory.size(max=TRUE)
rm(x)
gc()
system.time(x <- simplefactor(1e7))
memory.size(max=TRUE)
system.time(levels(x) <- c("x","y"))
memory.size(max=TRUE)
x[1:4]
memory.size(max=TRUE)
rm(x)
gc()
}
}
\references{
Writing R extensions -- System and foreign language interfaces
-- Handling R objects in C -- Attributes (Version 2.11.1 (2010-06-03 ) R
Development)
}
\seealso{
\code{\link{attr}} \code{\link{unattr}}
}
\author{
Jens Oehlschlägel
}
\keyword{attributes}
|
