Overloading methods in R
f <- function(...) UseMethod("f", NULL)
f.NULL <- function(...) {
args <- list(...)
classes <- sapply(args, class)
.Class <- paste(classes, collapse = ".")
NextMethod("f", ...)
}
f.numeric <- function(...) 2 * ..1
f.numeric.numeric <- function(...) ..1 + ..2
f.character.numeric.Date <- function(...) {
args <- list(...)
paste(args[[1]], args[[2]], format(args[[3]], "%Y-%m-%d"))
}
f.default <- function(...) print(list(...))
f(1) # 2
f(1,2) # 3
f("a", 23, Sys.Date()) # "a 23 2005-04-21"
f() # list()
Thanks Gabor! This answers a big part of my question. I am just curious why
something like this doesn't work in S4:
-------------------------
setGeneric("foo", function(object, ...) standardGeneric("foo"))
foo.NULL <- function(object, ...) {
args <- list(...)
classes <- sapply(args, class)
.Class <- paste(classes, collapse = ".")
}
foo.default <- function(object, ...) paste("wrong args!")
foo.numeric <- function(object, ...) 2 * ..1
foo.numeric.numeric <- function(object, ...) ..1 + ..2