What is S3 and S4 object system in R?

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#1

I am new to R. I read about S3 and S4 objects and methods and some of the article recommend to use S3 over S4. Can you please help me to understand these object systems in a better way?

Regards,
Imran


#2

Hi Imran,

I think this link can help you -

Regards,
Aayush


#3

Please see this to understand this better

http://adv-r.had.co.nz/OO-essentials.html

R’s three OO systems differ in how classes and methods are defined:

S3 implements a style of OO programming called generic-function OO. This is different from most programming languages, like Java, C++, and C#, which implement message-passing OO. With message-passing, messages (methods) are sent to objects and the object determines which function to call. Typically, this object has a special appearance in the method call, usually appearing before the name of the method/message: e.g., canvas.drawRect("blue"). S3 is different. While computations are still carried out via methods, a special type of function called a generic function decides which method to call, e.g., drawRect(canvas, "blue"). S3 is a very casual system. It has no formal definition of classes.

S4 works similarly to S3, but is more formal. There are two major differences to S3. S4 has formal class definitions, which describe the representation and inheritance for each class, and has special helper functions for defining generics and methods. S4 also has multiple dispatch, which means that generic functions can pick methods based on the class of any number of arguments, not just one.