Creating an S3 Method (1)

By itself, the generic function doesn't do anything. For that, you need to create methods, which are just regular functions with two conditions:

The name of the method must be of the form generic.class.
The method signature - that is, the arguments that are passed in to the method - must contain the signature of the generic.

The syntax is:

generic.class <- function(some, arguments, ...) {
  # Do something
}

This exercise is part of the course

Object-Oriented Programming with S3 and R6 in R

View Course

Exercise instructions

The generic get_n_elements() function has been defined in your workspace.

Type its name (without parentheses) to see how it works.
Write an S3 method to calculate the number of elements in a data.frame object.
- The name of the function should be the name of the generic, then a . then the name of the class of the input.
- The input arguments should be x and ....
- The body of the function should be a single line, returning the number of elements (rows times columns) in a data frame.
Call get_n_elements on the sleep (docs) dataset and assign the result to the variable n_elements_sleep.
Print n_elements_sleep to the console to see the result.

Hands-on interactive exercise

Have a go at this exercise by completing this sample code.

# View get_n_elements
get_n_elements

# Create a data.frame method for get_n_elements
___ <- ___




# Call the method on the sleep dataset
n_elements_sleep <- ___

# View the result
n_elements_sleep

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