Declare in R

In R, a class represents a blueprint for a data structure that provides various properties and methods that can be applied to the data. Here's how you can declare a class in R:

1. Using setClass() function: This is the most common way of defining a new class in R. Here's an example:

setClass("Person", 
         slots = c(name = "character", 
                   age = "integer",
                   gender = "character"))

Here we created a new class called Person and defined three slots or attributes for it: name, age, and gender. Each slot has a specific data type assigned to it.

2. Using setOldClass() function: This function is used to define a new class that inherits from an already defined class. Here's an example:

setOldClass("Employee", representation(name = "character",
                                        age = "integer",
                                        gender = "character"),
                                        class = "Person")

Here we created a new class called Employee that inherits from the Person class.

3. Using createClass() function: This function is used to create a new class that inherits from multiple parent classes. Here's an example:

setClass("Manager", 
         slots = c(department = "character",
                   subordinates = "list"),
         contains = c("Employee"))

Here we created a new class called Manager with two slots: department and subordinates. The class also inherits from the Employee and can access its properties and methods.

Once a class is defined, you can create objects or instances of that class using the new() function. For example:

person1 <- new("Person", name = "Alice", age = 25, gender = "Female")

Here we created a new object of the Person class named person1 and assigned values to its attributes.