Can someone show me how to create a vector of S4 objects or point me to an example? Reading Green Book 7.1.5 to me implied I could simply add "vector" to my object's representation. But it also implied that would have no change to the implementation of my class, but I did find a .Data slot defined afterwards (as though I had used "structure" instead). But I possibly just misunderstood that section. Given the following example class: require(methods) setClass("Foo", representation(id = "character", x = "integer", y = "integer")) Foo <- function(id = "", x, y) { new("Foo", id = id, x = as.integer(x), y = as.integer(y)) } Would prefer to internalize such that "Foo" contained a vector of its representation but something like this would be a compromise if that's easier to implement. foo.vec <- vector("Foo", 2) foo.vec[1] <- Foo("first",1,2) foo.vec[2] <- Foo("second",3,4) TIA ---------------------------------------------------------- SIGSIG -- signature too long (core dumped)