Question

I’m a R-newbie, and I was wondering if it is possible to create objects of own classes. When I read the “help(class)” it did not seem that classes like in Java are possible. I mean I want to have a class with methods, private variables and a constructor. For example it could look like this:

className <- class {
  # private variables
  var1 <- "standardvalue"

  var2 <- TRUE
  # Constructor
  constructor (v1, v2) {
    var1 <- v1
    var2 <- v2
  }

  # Method 1
  function sum() {
    var1 + var2
  }

  # Method 2
  function product() {
    var1 * var2
  }
}

In my main programm I want to create an Object of this Class and call it’s functions. For example like this:

# Create Object
numbers <- className(10,7)

# Call functions of the Object
numbers -> sum()      # Should give "17"
numbers -> product()  # Should give "70"

Is something like this possible? So far I did not fine any example.

Thanks for your help.

Answer 1

Yes, there are (at least) three OO systems to choose from in base R:

• S3
• S4
• ReferenceClasses

plus additional OO-like frameworks contributed via CRAN packages such as proto.

Please do some googling for S3, S4, ReferenceClasses, OO, …, possibly starting at rseek.org. All R programming books cover this too; my favourite is Chambers (2008) book titled “Software for Data Analysis”.