Logical (boolean) type in R Programming

Introduction

The logical type in R is used to represent true or false values. It helps you make decisions in your code.

Checking if a number is greater than another number.

Deciding whether to run a part of your program based on a condition.

Filtering data to keep only rows that meet a condition.

Storing answers to yes/no questions in your program.

Syntax

R Programming

variable <- TRUE
variable <- FALSE

Logical values in R are written as TRUE or FALSE (all uppercase).

You can also use T and F as shortcuts, but it's safer to use the full words.

Examples

This creates a logical variable x with the value TRUE and prints it.

R Programming

x <- TRUE
print(x)

This creates a logical variable y with the value FALSE and prints it.

R Programming

y <- FALSE
print(y)

This checks if 5 is greater than 3, which is TRUE, and stores it in z.

R Programming

z <- 5 > 3
print(z)

Sample Program

This program creates three logical variables and prints their values.

R Programming

a <- TRUE
b <- FALSE
c <- 10 == 10
print(a)
print(b)
print(c)

Important Notes

Logical values are useful in if statements and loops to control the flow of your program.

When you print logical values, R shows them as TRUE or FALSE with an index like [1].

Summary

Logical type stores TRUE or FALSE values.

Use logical values to make decisions in your code.

Logical expressions like comparisons return logical values.

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