S4 object system in R Programming - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the S4 object system in R?

S4 is a formal and rigorous object-oriented system in R that allows defining classes with explicit representation and methods with formal signatures.

beginner

How do you define a new S4 class in R?

Use the <code>setClass()</code> function with the class name and slots (attributes) specified as a named list of classes.

beginner

What is a slot in the S4 system?

A slot is a named component (attribute) of an S4 object that holds data of a specified class or type.

intermediate

How do you define a method for an S4 generic function?

Use <code>setMethod()</code> specifying the generic function name, the class signature for which the method applies, and the function implementation.

intermediate

What is the difference between S3 and S4 object systems in R?

S3 is informal and uses naming conventions for methods, while S4 is formal with explicit class definitions, slot types, and method signatures.

Which function is used to create a new S4 class in R?

A setClass()

B newClass()

C defineClass()

D createClass()

The setClass() function is used to define new S4 classes in R.

In S4, what is a 'slot'?

A A package dependency

B A method for an S4 class

C A generic function

D A named attribute of an S4 object

Slots are named components (attributes) of S4 objects that hold data.

Which function defines a method for an S4 generic function?

A setMethod()

B defineMethod()

C newMethod()

D createMethod()

The setMethod() function is used to define methods for S4 generics.

What is a key feature of S4 compared to S3?

A Uses only lists

B No method dispatch

C Formal class and method definitions

D No inheritance

S4 uses formal class definitions with explicit slots and method signatures.

How do you create an instance of an S4 class?

A Using the create() function

B Using the new() function

C Using the instantiate() function

D Using the build() function

The new() function creates instances of S4 classes.

Explain how to define an S4 class and create an object of that class in R.

Think about the functions used to define the class structure and to make an object.

Describe the difference between S3 and S4 object systems in R.

Focus on how strict and explicit each system is.