S3 object system in R Programming - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create an S3 object of class "person".

R Programming

person <- list(name = "Alice", age = 30)
class(person) <- [1]

Drag options to blanks, or click blank then click option'

A"Person"

Blist

Cperson

D"person"

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting to put the class name in quotes.

Using the wrong class name capitalization.

To create an S3 object, assign the class attribute as a character string with the class name, here "person".

2fill in blank

medium

Complete the code to define a print method for the "person" class.

R Programming

print.person <- function(x) {
  cat("Name:", x$name, "\nAge:", x$age, "\n")
}

p <- list(name = "Bob", age = 25)
class(p) <- "person"
print([1])

Drag options to blanks, or click blank then click option'

Ap

Bp$name

Cperson

Dprint.person

Attempts:

3 left

💡 Hint

Common Mistakes

Printing only a component like p$name instead of the whole object.

Trying to call the method name directly.

To call the print method for the S3 object, pass the object itself to print().

3fill in blank

hard

Fix the error in this S3 method definition for "summary.person".

R Programming

summary.person <- function(object, ...) {
  paste("Person:", object$name, "is", object$age, "years old")
}

p <- list(name = "Carol", age = 40)
class(p) <- "person"
summary([1])

Drag options to blanks, or click blank then click option'

Aobject

Bp

Cperson

Dsummary.person

Attempts:

3 left

💡 Hint

Common Mistakes

Passing the class name instead of the object to summary().

Using the method name directly instead of summary().

The summary function should be called with the object variable, here p, to dispatch the S3 method.

4fill in blank

hard

Fill both blanks to create an S3 object and check its class.

R Programming

obj <- list(value = 100)
class(obj) <- [1]
result <- class([2])

Drag options to blanks, or click blank then click option'

A"myclass"

Bobj

C"obj"

Dvalue

Attempts:

3 left

💡 Hint

Common Mistakes

Using the object name as a string when assigning class.

Checking class of a string instead of the object.

Assign the class name as a string to obj, then check the class of obj itself.

5fill in blank

hard

Fill all three blanks to define a generic function and an S3 method, then call it.

R Programming

myfunc <- function(x) {
  UseMethod([1])
}

myfunc.[2] <- function(x) {
  paste("Called method for class", class(x))
}

obj <- list()
class(obj) <- [3]
myfunc(obj)

Drag options to blanks, or click blank then click option'

A"myfunc"

Bmyclass

C"myclass"

Dmyfunc

Attempts:

3 left

💡 Hint

Common Mistakes

Passing the generic function name as a string to UseMethod().

Not quoting the class name when assigning class.

Mismatch between class name and method suffix.

UseMethod() needs the generic function name without quotes; method name uses class name; class assigned as string.