# Attribute setting by reference Function `setattr` sets a singe attribute and function `setattributes` sets a list of attributes. ```r getsetattr(x, which, value) setattr(x, which, value) setattributes(x, attributes) ``` ## Arguments - `x`: an R object - `which`: name of the attribute - `value`: value of the attribute, use NULL to remove this attribute - `attributes`: a named list of attribute values ## Returns 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. ## Details The attributes of 'x' are changed in place without copying x. function `setattributes` does only change the named attributes, it does not delete the non-names attributes like `attributes` does. ## Functions * `setattr()`: * `setattributes()`: ## Examples ```r 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 ## Not run: # 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() ## End(Not run) ``` ## References Writing R extensions -- System and foreign language interfaces -- Handling R objects in C -- Attributes (Version 2.11.1 (2010-06-03 ) R Development) ## See Also `attr` `unattr` ## Author(s) Jens Oehlschlägel

getsetattr function