If-else statements in R Programming - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of nested if-else in R

What is the output of this R code?

R Programming

x <- 7
if (x > 10) {
  print("Greater than 10")
} else if (x > 5) {
  print("Between 6 and 10")
} else {
  print("5 or less")
}

A [1] "Between 6 and 10"

B [1] "Greater than 10"

C [1] "5 or less"

D Error in if (x > 10) { : missing value where TRUE/FALSE needed

💡 Hint

Check the conditions in order and see which one matches the value of x.

The variable x is 7, which is not greater than 10, so the first if fails. The else if checks if x is greater than 5, which is true, so it prints "Between 6 and 10".

❓ Predict Output

intermediate

Output of if-else with vector condition

What happens when you run this R code?

R Programming

x <- c(3, 7, 12)
if (x > 5) {
  print("Some values are greater than 5")
} else {
  print("No values greater than 5")
}

A Warning: the condition has length > 1 and only the first element will be used

B [1] "No values greater than 5"

C [1] "Some values are greater than 5"

D NULL

💡 Hint

Remember that if expects a single TRUE or FALSE, not a vector.

The condition x > 5 returns a vector of logicals. Using it directly in if causes a warning and only the first element is used.

🔧 Debug

advanced

Identify the error in this if-else code

What error does this R code produce?

R Programming

x <- 4
if x > 3 {
  print("x is greater than 3")
} else {
  print("x is 3 or less")
}

A Error: object 'x' not found

B Error in if (x > 3) { : missing value where TRUE/FALSE needed

C SyntaxError: unexpected symbol in "if x"

D No error, prints "x is greater than 3"

💡 Hint

Check the syntax of the if statement in R.

In R, the condition in if must be inside parentheses. Writing 'if x > 3' without parentheses causes a syntax error.

🧠 Conceptual

advanced

Behavior of if-else with NA condition

What is the output of this R code?

R Programming

x <- NA
if (x) {
  print("True")
} else {
  print("False")
}

A [1] "True"

B NULL

C [1] "False"

D Error in if (x) { : missing value where TRUE/FALSE needed

💡 Hint

Think about how R treats NA in logical conditions.

NA is an unknown logical value. Using it directly in if causes an error because R cannot decide TRUE or FALSE.

❓ Predict Output

expert

Output of complex nested if-else with multiple variables

What is the output of this R code?

R Programming

a <- 5
b <- 10
if (a > 3) {
  if (b < 5) {
    print("a > 3 and b < 5")
  } else if (b < 15) {
    print("a > 3 and b between 5 and 15")
  } else {
    print("a > 3 and b >= 15")
  }
} else {
  print("a <= 3")
}

A [1] "a > 3 and b < 5"

B [1] "a > 3 and b between 5 and 15"

C [1] "a > 3 and b >= 15"

D [1] "a <= 3"

💡 Hint

Check the values of a and b and follow the nested conditions carefully.

a is 5 which is > 3, so the outer if is true. Then b is 10, which is not < 5 but is < 15, so the second condition matches and prints "a > 3 and b between 5 and 15".