S3 Classes

> Univariate <- function(x) {
+     object <- list(name = x)
+     class(object) <- x
+     return(object)
+ }
> printDist <- function(x) {
+     if (is.null(attr(x, "class"))) {
+         print("BOSS, INPUT THE DISTRIBUTION")
+     }
+     else UseMethod("printDist", x)
+ }
> printDist.Discrete <- function(x) {
+     print("In Discrete")
+     NextMethod()
+ }
> printDist.Poisson <- function(x) {
+     print("POISSON DISTRIBUTION")
+ }
> x <- Univariate(c("Discrete", "Poisson"))
> printDist(x)
[1] "In Discrete"
[1] "POISSON DISTRIBUTION"
> x <- Univariate(c("Continous", "Poisson"))
> printDist(x)
[1] "POISSON DISTRIBUTION"
> x <- Univariate(c("Continous", "Poisson"))
> printDist(x)
[1] "POISSON DISTRIBUTION"

> myclass <- function(x, n) {
+     structure(x, class = "myclass", n = n)
+ }
> c.myclass <- function(..., recursive = FALSE) {
+     dots <- list(...)
+     ns <- sapply(dots, attr, which = "n")
+     classes <- rep("myclass", length(dots))
+     res <- structure(unlist(dots, recursive = FALSE), class = classes)
+     attr(res, "n") <- ns
+     return(res)
+ }
> `[.myclass` <- function(x, i) {
+     y <- unclass(x)[i]
+     ns <- attr(x, "n")[i]
+     class(y) <- "myclass"
+     attr(y, "n") <- ns
+     return(y)
+ }
> x1 <- myclass(1, 5)
> x2 <- myclass(2, 6)
> print(c(x1, x2)[2])
[1] 2
attr(,"class")
[1] "myclass"
attr(,"n")
[1] 6
> z <- c(x1, x2)
> print(attr(z, "class"))
[1] "myclass" "myclass"
> print(attr(z, "n"))
[1] 5 6

> geom <- function(x, ...) UseMethod("geom")
> geom.default <- function(x, ...) {
+     object <- list(area = x^2)
+     class(object) <- "geom"
+     return(object)
+ }
> geom.rectangle <- function(x, ...) {
+     args <- list(...)
+     object <- list(area = x * as.numeric(args[1]))
+     class(object) <- "geom"
+     return(object)
+ }
> geom.triangle <- function(x, ...) {
+     args <- list(...)
+     object <- list(area = (x * as.numeric(args[1]) * as.numeric(args[2]))/2)
+     class(object) <- "geom"
+     return(object)
+ }
> my.object1 <- geom(3)
> print(my.object1)
$area
[1] 9

attr(,"class")
[1] "geom"
> print(attr(my.object1, "class"))
[1] "geom"
> my.object2 <- geom.rectangle(3, 4)
> print(my.object2)
$area
[1] 12

attr(,"class")
[1] "geom"
> print(attr(my.object2, "class"))
[1] "geom"
> my.object3 <- geom.triangle(3, 4, 5)
> print(my.object3)
$area
[1] 30

attr(,"class")
[1] "geom"
> print(attr(my.object3, "class"))
[1] "geom"