Logical operators (&, |, !, &&, ||) in R Programming - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of vectorized logical AND (&) vs. element-wise AND (&&)

What is the output of the following R code snippet?

R Programming

x <- c(TRUE, FALSE, TRUE)
y <- c(FALSE, TRUE, TRUE)
result <- x & y
result2 <- x && y
print(result)
print(result2)

A

[1] FALSE FALSE TRUE
[1] FALSE

B

[1] TRUE TRUE TRUE
[1] TRUE

C

[1] FALSE TRUE FALSE
[1] TRUE

D

[1] TRUE FALSE TRUE
[1] FALSE

💡 Hint

Remember that & works element-wise on vectors, while && only checks the first element.

The & operator compares each element of x and y, producing a vector of logicals. The && operator only compares the first element of each vector, returning a single logical value.

❓ Predict Output

intermediate

Output of logical OR (|) with mixed TRUE and FALSE vectors

What will be printed by this R code?

R Programming

a <- c(FALSE, FALSE, TRUE)
b <- c(TRUE, FALSE, FALSE)
print(a | b)

A [1] FALSE TRUE TRUE

B [1] TRUE FALSE TRUE

C [1] TRUE TRUE TRUE

D [1] FALSE FALSE FALSE

💡 Hint

The | operator compares each element and returns TRUE if either is TRUE.

Element-wise OR returns TRUE if at least one element in the pair is TRUE. So positions: FALSE|TRUE=TRUE, FALSE|FALSE=FALSE, TRUE|FALSE=TRUE.

❓ Predict Output

advanced

Effect of ! (NOT) operator on a logical vector

What is the output of this R code?

R Programming

flags <- c(TRUE, FALSE, TRUE, FALSE)
negated <- !flags
print(negated)

A [1] FALSE TRUE FALSE TRUE

B [1] TRUE FALSE TRUE FALSE

C [1] FALSE FALSE FALSE FALSE

D [1] TRUE TRUE TRUE TRUE

💡 Hint

The ! operator flips TRUE to FALSE and FALSE to TRUE.

The NOT operator reverses each logical value in the vector.

❓ Predict Output

advanced

Difference between & and && in conditional statements

What will this R code print?

R Programming

x <- c(TRUE, FALSE)
if (x & TRUE) {
  print("A")
} else {
  print("B")
}
if (x && TRUE) {
  print("C")
} else {
  print("D")
}

A

B
C

B

B
D

C

A
C

D

A
D

💡 Hint

Remember that if expects a single TRUE or FALSE, && returns a single logical, & returns a vector.

The if with (x & TRUE) produces c(TRUE, FALSE), R warns and uses the first element TRUE, printing "A". The if with (x && TRUE) evaluates first elements TRUE && TRUE = TRUE, printing "C".

🧠 Conceptual

expert

Understanding short-circuit behavior of && and || in R

Which statement best describes the behavior of the && and || operators in R?

A && and || cannot be used in if statements because they return vectors.

B && and || are identical to & and | in all contexts.

C && and || evaluate all elements of logical vectors and return a vector of results.

D && and || evaluate only the first element of logical vectors and perform short-circuit evaluation.

💡 Hint

Think about how && and || behave differently from & and | when used in conditions.

In R, && and || only check the first element of logical vectors and stop evaluating further if the result is already determined (short-circuit). This makes them suitable for control flow statements like if.