Function definition in R Programming - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of a simple function call

What is the output of the following R code?

R Programming

multiply_by_two <- function(x) {
  return(x * 2)
}

result <- multiply_by_two(5)
print(result)

A [1] 10

B [1] 7

C Error in multiply_by_two(5) : could not find function "multiply_by_two"

D [1] 25

💡 Hint

Think about what the function does to the input number.

The function multiply_by_two takes an input x and returns x multiplied by 2. So multiply_by_two(5) returns 10.

❓ Predict Output

intermediate

Function with default argument

What will be printed when this R code runs?

R Programming

greet <- function(name = "Guest") {
  print(paste("Hello," , name))
}

greet()
greet("Alice")

A

[1] "Hello, Guest"
[1] "Hello, Alice"

B

[1] "Hello, "
[1] "Hello, Alice"

C Error: object 'name' not found

D

[1] "Hello, Alice"
[1] "Hello, Guest"

💡 Hint

Check what happens when no argument is given.

The function greet uses a default value 'Guest' for the parameter name. Calling greet() prints 'Hello, Guest'. Calling greet("Alice") prints 'Hello, Alice'.

❓ Predict Output

advanced

Function with variable scope

What is the output of this R code?

R Programming

x <- 10

add_to_x <- function(y) {
  x <- 5
  return(x + y)
}

result <- add_to_x(3)
print(result)
print(x)

A

[1] 13
[1] 10

B

[1] 8
[1] 10

C

[1] 8
[1] 5

D

[1] 13
[1] 5

💡 Hint

Remember that variables inside functions have local scope.

Inside the function, x is set to 5 locally. So add_to_x(3) returns 5 + 3 = 8. The global x remains 10, so print(x) outputs 10.

❓ Predict Output

advanced

Function with missing return statement

What will this R code print?

R Programming

sum_values <- function(a, b) {
  a + b
}

result <- sum_values(4, 6)
print(result)

A Error: object 'result' not found

B NULL

C [1] 10

D [1] 46

💡 Hint

In R, the last expression is returned even without return().

In R, if there is no explicit return(), the last evaluated expression is returned. So sum_values(4, 6) returns 10.

🧠 Conceptual

expert

Error type from incorrect function call

What error will this R code produce when run?

R Programming

my_function <- function(x, y) {
  return(x + y)
}

my_function(5)

A No error, returns 5

B Error in my_function(5) : object 'y' not found

C Warning: unused argument (5)

D Error in my_function(5) : argument "y" is missing, with no default

💡 Hint

Check if all required arguments are provided.

The function requires two arguments x and y. Calling it with only one argument causes an error about missing argument y.