Default argument values in R Programming - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of function with default argument

What is the output of this R code when calling greet()?

R Programming

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

A "Hello friend"

B "Hello name"

C Error: object 'name' not found

D "Hello"

💡 Hint

Check what value the function uses when no argument is given.

The function greet has a default argument 'name' set to "friend". Calling greet() uses this default and returns "Hello friend".

❓ Predict Output

intermediate

Effect of missing argument with default

What will be the output of this R code?

R Programming

multiply <- function(x, y = 2) {
  x * y
}
multiply(5)

A Error: argument 'y' missing

B 10

C 5

D NULL

💡 Hint

Look at the default value of y and how multiply is called.

The function multiply uses y=2 by default. Calling multiply(5) means x=5 and y=2, so 5*2=10.

🔧 Debug

advanced

Identify the error in default argument usage

What error does this R code produce when run?

R Programming

f <- function(x = y, y = 3) {
  x + y
}
f()

A Error: argument 'x' missing

B 3

C 6

D Error: object 'y' not found

💡 Hint

Default arguments are evaluated when the function is called, in order.

The default value for x is y, but y is not defined before x's default is evaluated, causing an error.

❓ Predict Output

advanced

Output with default argument as a function call

What is the output of this R code?

R Programming

get_default <- function() {
  7
}
add <- function(x, y = get_default()) {
  x + y
}
add(3)

A 10

B 3

C Error: object 'get_default' not found

D NULL

💡 Hint

Default arguments can be set by calling other functions.

The default value for y is the result of get_default(), which returns 7. So add(3) returns 3+7=10.

🧠 Conceptual

expert

Understanding evaluation timing of default arguments

Consider this R code. What is the value of result after running it?

R Programming

x <- 5
f <- function(y = x) {
  x <- 10
  y
}
result <- f()

A Error: object 'x' not found

B 10

C 5

D NULL

💡 Hint

Default arguments are evaluated when the function is called, before the function body runs.

The default argument y = x uses the global x = 5 at call time. The local x = 10 inside the function does not affect y's default.