Running R code in R Programming - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of a simple R loop

What is the output of the following R code?

R Programming

result <- c()
for(i in 1:4) {
  result <- c(result, i^2)
}
print(result)

A [1] 1 2 3 4

B [1] 1 8 27 64

C [1] 2 4 6 8

D [1] 1 4 9 16

💡 Hint

Think about what i^2 means inside the loop.

The loop squares each number from 1 to 4 and appends it to the result vector. So the output is the squares: 1, 4, 9, 16.

🧠 Conceptual

intermediate

Understanding R function return values

What will be the output when running this R code?

R Programming

my_func <- function(x) {
  y <- x + 2
  z <- y * 3
  z
  y
}
print(my_func(4))

A [1] 6

B [1] 18

C [1] 12

D [1] 0

💡 Hint

Remember that R returns the last evaluated expression in a function.

The function calculates y = 6 and z = 18, but the last line is y, so the function returns 6.

🔧 Debug

advanced

Identify the error in R code

What error does this R code produce when run?

R Programming

x <- c(1, 2, 3)
print(x[4])

A Error: subscript out of bounds

B NA (no error, prints NA)

C NULL

D SyntaxError

💡 Hint

What happens when you access an index outside the vector length in R?

In R, accessing an index beyond the vector length returns NA, not an error.

❓ Predict Output

advanced

Output of nested if-else in R

What is the output of this R code?

R Programming

x <- 5
if (x > 3) {
  if (x < 10) {
    print("Between 4 and 9")
  } else {
    print("10 or more")
  }
} else {
  print("3 or less")
}

A "Between 4 and 9"

B "10 or more"

C Error: unexpected symbol

D "3 or less"

💡 Hint

Check the conditions carefully and their order.

x is 5, which is greater than 3 and less than 10, so the first print runs.

🚀 Application

expert

Calculate the sum of even numbers using R code

Which option correctly calculates the sum of even numbers from 1 to 10 in R?

A sum(c(2,4,6,8,10))

B sum(1:10 %% 2 == 0)

C sum(seq(2, 10, by=2))

D sum(1:10[1:10 %% 2 == 0])

💡 Hint

Use seq() to generate even numbers or filter with modulo operator.

Option C generates even numbers from 2 to 10 and sums them correctly. Option C sums logical TRUE/FALSE values, giving count not sum. Option C is correct but hardcoded, option C has syntax error.