Defining methods for an S4 class
When a new class is defined, the data elements are defined, but the methods associated with the class are defined on a separate stage. Methods are implemented in a manner similar to the one used for S3 classes. A function is defined, and the way the function reacts depends on its arguments. If a method is used to change one of the data components of an object, then it must return a copy of the object, just as we saw with S3 classes.
The creation of new methods is discussed in two steps. We will first discuss how to define a method for a class where the method does not yet exist. Next, we will discuss some predefined methods that are available and how to extend them to accommodate a new class.
Defining new methods
The first step to create a new method is to reserve the name. Some functions are included by default, such as the initialize, print or show commands, and we will later see how to extend them. To reserve a new name, you must first use the setGeneric...
