Code chunks and output in R Programming - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of a simple code chunk

What is the output of this R code chunk?

R Programming

x <- 5
x * 3

A [1] 53

B [1] 8

C [1] 15

D Error in x * 3 : non-numeric argument to binary operator

💡 Hint

Remember that * means multiplication in R.

The variable x is assigned the value 5. Multiplying 5 by 3 gives 15, so the output is [1] 15.

❓ Predict Output

intermediate

Output of a code chunk with a function

What is the output of this R code chunk?

R Programming

square <- function(n) {
  return(n^2)
}
square(4)

A [1] 16

B [1] 4

C Error: object 'square' not found

D [1] 8

💡 Hint

The function returns the square of the input number.

The function square returns the input number raised to the power of 2. 4 squared is 16.

❓ Predict Output

advanced

Output of a code chunk with vector recycling

What is the output of this R code chunk?

R Programming

v1 <- c(1, 2, 3)
v2 <- c(4, 5)
v1 + v2

A Error in v1 + v2 : non-conformable arrays

B [1] 5 7 8

C [1] 5 7 3

D [1] 5 7 7

💡 Hint

R recycles the shorter vector to match the length of the longer vector.

v2 is recycled to c(4,5,4). Adding element-wise: 1+4=5, 2+5=7, 3+4=7.

❓ Predict Output

advanced

Output of a code chunk with a factor variable

What is the output of this R code chunk?

R Programming

f <- factor(c('low', 'medium', 'high', 'medium'), levels = c('low', 'medium', 'high'))
levels(f)[2] <- 'mid'
f

A

[1] low  medium high medium
Levels: low medium high

B

[1] low  mid  high mid 
Levels: low mid high

C

[1] low  mid  high mid 
Levels: low medium high

D Error in levels(f)[2] <- 'mid' : replacement has length zero

💡 Hint

Changing the second level name changes the factor labels accordingly.

The second level 'medium' is renamed to 'mid'. The factor values update to reflect this change.

❓ Predict Output

expert

Output of a code chunk with nested functions and environment

What is the output of this R code chunk?

R Programming

outer <- function(x) {
  inner <- function(y) {
    x + y
  }
  inner(10)
}
outer(5)

A [1] 15

B [1] 5

C Error: object 'y' not found

D [1] 10

💡 Hint

The inner function uses x from the outer function's environment.

The outer function defines x=5 and calls inner(10). Inner adds x + y = 5 + 10 = 15.