Environment and closures in R Programming - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a function that returns another function adding a fixed number.

R Programming

makeAdder <- function(x) {
  function(y) {
    return(y [1] x)
  }
}

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

A+

B-

C*

D/

Attempts:

3 left

💡 Hint

Common Mistakes

Using subtraction or multiplication instead of addition.

Forgetting to use the operator between y and x.

The inner function adds y and x. The + operator is needed.

2fill in blank

medium

Complete the code to assign a value to a variable in the parent environment inside a closure.

R Programming

counter <- function() {
  count <- 0
  function() {
    count [1] count + 1
    return(count)
  }
}

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

A->

B=

C<-

D<<-

Attempts:

3 left

💡 Hint

Common Mistakes

Using <- which creates a new local variable instead of updating the parent.

Using = which does not assign in the parent environment.

The <<− operator assigns the value to count in the parent environment, allowing the counter to update.

3fill in blank

hard

Fix the error in the closure that tries to access a variable from the wrong environment.

R Programming

makeMultiplier <- function(factor) {
  function(x) {
    return(x * [1])
  }
}

mult2 <- makeMultiplier(2)
mult2(5)

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

Afactor

Bx

CmakeMultiplier

Dmult2

Attempts:

3 left

💡 Hint

Common Mistakes

Using x instead of factor inside the return statement.

Using the function names instead of variables.

The inner function must use factor from the parent environment to multiply x.

4fill in blank

hard

Fill both blanks to create a closure that stores and retrieves a value.

R Programming

makeStorage <- function() {
  value <- NULL
  list(
    set = function(x) {
      value [1] x
    },
    get = function() {
      return(value [2])
    }
  )
}

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

A<<-

Bvalue

Creturn

D<-

Attempts:

3 left

💡 Hint

Common Mistakes

Using <- in set which creates a local variable.

Not returning the stored value in get.

The set function uses <<− to update value in the parent environment. The get function returns value.

5fill in blank

hard

Fill all three blanks to create a closure that counts how many times it has been called and returns the count.

R Programming

makeCounter <- function() {
  count <- 0
  function() {
    count [1] count + 1
    return([2])
  }
}

counter <- makeCounter()
counter()
counter()  # returns [3]

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

A<-

Bcount

C<<-

D2

Attempts:

3 left

💡 Hint

Common Mistakes

Using <- which does not update the parent variable.

Returning a literal number instead of the count variable.

Incorrect expected return value after two calls.

The counter updates count in the parent environment using <<−. It returns the updated count. After two calls, the count is 2.