Logical (boolean) type in R Programming - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of logical operations in R

What is the output of the following R code?

R Programming

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

A [1] TRUE TRUE TRUE

B [1] TRUE FALSE TRUE

C [1] FALSE FALSE TRUE

D [1] FALSE TRUE FALSE

💡 Hint

Remember that '&' is element-wise AND in R.

The '&' operator compares each element of x and y and returns TRUE only if both are TRUE.

Here, the pairs are (TRUE, FALSE), (FALSE, FALSE), (TRUE, TRUE), so the results are FALSE, FALSE, TRUE.

❓ Predict Output

intermediate

Result of logical negation in R

What will be printed by this R code?

R Programming

flag <- c(TRUE, FALSE, FALSE, TRUE)
neg_flag <- !flag
print(neg_flag)

A [1] FALSE FALSE FALSE FALSE

B [1] FALSE TRUE TRUE FALSE

C [1] TRUE FALSE FALSE TRUE

D [1] TRUE TRUE TRUE TRUE

💡 Hint

The '!' operator flips TRUE to FALSE and vice versa.

The '!' operator negates each element in the logical vector.

So TRUE becomes FALSE, and FALSE becomes TRUE.

❓ Predict Output

advanced

Logical vector recycling in R

What is the output of this R code snippet?

R Programming

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

A [1] TRUE FALSE TRUE FALSE

B [1] TRUE TRUE TRUE TRUE

C [1] TRUE TRUE FALSE FALSE

D [1] TRUE TRUE TRUE FALSE

💡 Hint

Remember R recycles shorter vectors to match the length of longer vectors.

The vector a is recycled to length 4: TRUE, FALSE, TRUE, FALSE.

Then element-wise OR with b gives TRUE, TRUE, TRUE, FALSE.

❓ Predict Output

advanced

Logical indexing with boolean vectors in R

What will this R code print?

R Programming

values <- c(10, 20, 30, 40, 50)
filter <- c(TRUE, FALSE, TRUE, FALSE, TRUE)
selected <- values[filter]
print(selected)

A [1] 10 30 50

B [1] 20 40

C [1] 10 20 30 40 50

D [1] 30 50

💡 Hint

Logical vectors can be used to pick elements from another vector.

The logical vector filter selects elements where it is TRUE.

So elements 1, 3, and 5 from values are selected.

🧠 Conceptual

expert

Understanding the difference between '&' and '&&' in R

Which statement best describes the difference between '&' and '&&' in R?

A '&' performs element-wise logical AND on vectors; '&&' evaluates only the first element of each vector.

B '&' performs logical OR; '&&' performs logical AND.

C '&' and '&&' are interchangeable and produce the same result for all inputs.

D '&' is used only for single logical values; '&&' works on vectors element-wise.

💡 Hint

Think about how R treats vectorized logical operations versus single comparisons.

The single ampersand '&' compares each element of vectors and returns a vector of results.

The double ampersand '&&' only compares the first element of each vector and returns a single TRUE or FALSE.

Practice

1. What type of values does the logical type in R store?

easy

A. Numbers only

B. TRUE or FALSE

C. Text strings

D. Dates and times

Solution

1. Step 1: Understand logical type meaning

   Logical type in R is used to store values that represent truth values.

2. Step 2: Identify stored values

   These truth values are either TRUE or FALSE, not numbers, text, or dates.

3. Final Answer:

   TRUE or FALSE -> Option B

4. Quick Check:

   Logical type = TRUE or FALSE [OK]

Hint: Logical means true or false values only [OK]

Common Mistakes:

• Confusing logical with numeric type
• Thinking logical stores text
• Assuming logical stores dates

2. Which of the following is the correct way to create a logical vector in R?

easy

A. c('TRUE', 'FALSE')

B. c(1, 0, 1)

C. c(TRUE, FALSE, TRUE)

D. c(T, F, 'TRUE')

Solution

1. Step 1: Check vector creation syntax

   Logical vectors use TRUE or FALSE values without quotes inside c().

2. Step 2: Validate each option

   c(TRUE, FALSE, TRUE) uses proper logical values TRUE and FALSE. c('TRUE', 'FALSE') creates character vector. c(1, 0, 1) creates numeric vector. c(T, F, 'TRUE') mixes logical shortcuts T, F with string 'TRUE' coercing to character vector.

3. Final Answer:

   c(TRUE, FALSE, TRUE) -> Option C

4. Quick Check:

   Logical vector uses TRUE/FALSE without quotes [OK]

Hint: Use TRUE/FALSE without quotes for logical vectors [OK]

Common Mistakes:

• Using numbers instead of logical values
• Putting TRUE/FALSE in quotes
• Mixing logical and string types

3. What is the output of this R code?

result <- 5 > 3
print(result)

medium

A. TRUE

B. "TRUE"

C. FALSE

D. Error

Solution

1. Step 1: Evaluate the comparison 5 > 3

   Since 5 is greater than 3, the expression returns TRUE as a logical value.

2. Step 2: Understand print output

   print() outputs the logical value TRUE without quotes.

3. Final Answer:

   TRUE -> Option A

4. Quick Check:

   5 > 3 = TRUE [OK]

Hint: Comparison returns logical TRUE or FALSE, not strings [OK]

Common Mistakes:

• Thinking output is string "TRUE"
• Confusing TRUE with FALSE
• Expecting an error from comparison

4. Identify the error in this R code snippet:

flag <- TRUE
if flag == TRUE {
  print("Yes")
}

medium

A. Variable flag is not defined

B. Incorrect logical value TRUE

C. print() function is wrong

D. Missing parentheses around condition in if statement

Solution

1. Step 1: Check if statement syntax in R

   In R, the condition in if() must be inside parentheses.

2. Step 2: Identify missing parentheses

   The code uses if flag == TRUE without parentheses, causing syntax error.

3. Final Answer:

   Missing parentheses around condition in if statement -> Option D

4. Quick Check:

   if() needs parentheses [OK]

Hint: Always put condition inside parentheses in if() [OK]

Common Mistakes:

• Omitting parentheses in if condition
• Misusing TRUE value
• Assuming print() syntax is wrong

5. Given a numeric vector nums <- c(0, 1, 2, 3, 0), which R expression correctly creates a logical vector indicating which elements are non-zero?

hard

A. nums != 0

B. nums == TRUE

C. is.logical(nums)

D. nums > TRUE

Solution

1. Step 1: Understand the goal

   We want a logical vector showing TRUE where elements are not zero.

2. Step 2: Evaluate each option

   nums != 0 returns TRUE for non-zero elements. nums == TRUE compares to 1 (TRUE coerces to 1), TRUE only where nums==1. is.logical(nums) checks type of nums, returns single FALSE since it's numeric. nums > TRUE compares to 1, TRUE only where nums > 1.

3. Final Answer:

   nums != 0 -> Option A

4. Quick Check:

   nums != 0 gives logical TRUE for non-zero [OK]

Hint: Use != 0 to find non-zero elements logically [OK]

Common Mistakes:

• Using == TRUE to compare numbers
• Using is.logical() to check or create logical vector
• Comparing numbers directly to TRUE