Variable assignment (<- and =) in R Programming - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of variable assignment with <- and =

What is the output of the following R code?

x <- 5
y = 10
z <- x + y
print(z)

R Programming

x <- 5
y = 10
z <- x + y
print(z)

A NULL

B 510

C Error: object 'z' not found

D 15

💡 Hint

Remember that both <- and = assign values to variables in R.

Both <- and = assign values to variables in R. Here, x is 5, y is 10, so z is 15.

❓ Predict Output

intermediate

Difference between <- and = in function arguments

What will this R code print?

f <- function(a = 3) { a * 2 }
f()
f <- function(a <- 3) { a * 2 }
f()

R Programming

f <- function(a = 3) { a * 2 }
f()
f <- function(a <- 3) { a * 2 }
f()

A 6 and Error

B 6 and 6

C Error and 6

D Error and Error

💡 Hint

Check how default arguments are assigned in R functions.

In R, default arguments use =, not <-. Using <- in function arguments causes an error.

🔧 Debug

advanced

Why does this assignment fail?

Consider this R code:

5 <- x

Why does this cause an error?

R Programming

5 <- x

A Because <- cannot be used with numbers

B Because x is not defined

C Because 5 is a constant and cannot be assigned a value

D Because assignment requires = not <-

💡 Hint

Think about what can be on the left side of an assignment.

In R, the left side of <- must be a variable name, not a constant like 5.

❓ Predict Output

advanced

Output of chained assignments

What is the output of this R code?

a <- b <- 7
print(a)
print(b)

R Programming

a <- b <- 7
print(a)
print(b)

A 7 and 7

B 7 and NULL

C NULL and 7

D Error: object 'b' not found

💡 Hint

Remember that assignment in R returns the assigned value.

The expression b <- 7 assigns 7 to b and returns 7, which is then assigned to a. Both a and b become 7.

📝 Syntax

expert

Which assignment causes a syntax error?

Which of these R assignments will cause a syntax error?

A x <- 10

B <- z 30

C y = 20

D a <- b <- 5

💡 Hint

Look carefully at the position of the assignment operator.

The assignment operator <- must be between variable and value. '<- z 30' is invalid syntax.