Comparison operators in R Programming - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of vector comparison with recycling

What is the output of this R code?

c(1, 2, 3, 4) > c(2, 2)

R Programming

c(1, 2, 3, 4) > c(2, 2)

A [1] TRUE TRUE TRUE TRUE

B [1] TRUE FALSE TRUE FALSE

C [1] FALSE FALSE TRUE TRUE

D [1] FALSE TRUE TRUE TRUE

💡 Hint

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

The shorter vector c(2, 2) is recycled to c(2, 2, 2, 2). Then element-wise comparison is done: 1>2 is FALSE, 2>2 is FALSE, 3>2 is TRUE, 4>2 is TRUE.

❓ Predict Output

intermediate

Output of chained comparison operators

What is the output of this R code?

5 > 3 & 2 < 4

R Programming

5 > 3 & 2 < 4

A [1] TRUE

B [1] FALSE

C [1] TRUE TRUE

D [1] FALSE FALSE

💡 Hint

The & operator checks if both conditions are TRUE.

5 > 3 is TRUE and 2 < 4 is TRUE, so TRUE & TRUE returns TRUE.

❓ Predict Output

advanced

Output of comparison with NA values

What is the output of this R code?

c(1, NA, 3) == 3

R Programming

c(1, NA, 3) == 3

A [1] FALSE NA TRUE

B [1] FALSE FALSE TRUE

C [1] TRUE NA TRUE

D [1] NA NA TRUE

💡 Hint

Comparisons with NA produce NA unless the value is known to be equal or not.

1 == 3 is FALSE, NA == 3 is NA (unknown), 3 == 3 is TRUE.

❓ Predict Output

advanced

Output of comparing factors with different levels

What is the output of this R code?

f1 <- factor(c("a", "b"))
f2 <- factor(c("b", "a"))
f1 == f2

R Programming

f1 <- factor(c("a", "b"))
f2 <- factor(c("b", "a"))
f1 == f2

A [1] FALSE TRUE

B [1] TRUE TRUE

C [1] TRUE FALSE

D [1] FALSE FALSE

💡 Hint

Factors compare underlying integer codes, not just labels.

f1 has levels a=1, b=2 so codes 1,2. f2 has levels b=1, a=2 so first element 'b' (code 1), second 'a' (code 2), codes 1,2. Thus 1==1 TRUE, 2==2 TRUE.

🧠 Conceptual

expert

Behavior of comparison operators with matrices

Given two matrices:

m1 <- matrix(1:4, nrow=2)
m2 <- matrix(c(2, 2, 3, 3), nrow=2)

What is the output of m1 >= m2?

R Programming

m1 <- matrix(1:4, nrow=2)
m2 <- matrix(c(2, 2, 3, 3), nrow=2)
m1 >= m2

A

     [,1]  [,2]
[1,] FALSE FALSE
[2,]  TRUE  TRUE

B

     [,1]  [,2]
[1,] FALSE  TRUE
[2,]  TRUE  TRUE

C

     [,1]  [,2]
[1,]  TRUE FALSE
[2,] FALSE  TRUE

D

     [,1]  [,2]
[1,]  TRUE  TRUE
[2,] FALSE FALSE

💡 Hint

Comparison is element-wise between corresponding elements of matrices.

m1 is matrix: [,1] [,2] [1,] 1 3 [2,] 2 4 m2 is matrix: [,1] [,2] [1,] 2 3 [2,] 2 3 Comparisons: 1 >= 2 is FALSE 3 >= 3 is TRUE 2 >= 2 is TRUE 4 >= 3 is TRUE So output matrix is: [,1] [,2] [1,] FALSE TRUE [2,] TRUE TRUE

Practice

1. Which of the following comparison operators in R checks if two values are equal?

easy

A. !=

B. =

C. <>

D. ==

Solution

1. Step 1: Understand equality operator in R

   In R, the operator to check if two values are equal is ==.

2. Step 2: Differentiate from other operators

   = is for assignment, != means not equal, and <> is not valid in R.

3. Final Answer:

   == -> Option D

4. Quick Check:

   Equality operator = == [OK]

Hint: Use double equals (==) to test equality in R [OK]

Common Mistakes:

• Using single = instead of ==
• Confusing != with equality
• Using <> which is invalid in R

2. Which of the following is the correct syntax to check if variable x is NOT equal to 10 in R?

easy

A. x != 10

B. x <> 10

C. x =! 10

D. x !== 10

Solution

1. Step 1: Identify the not equal operator in R

   R uses != to check if two values are not equal.

2. Step 2: Check syntax correctness

   <> and !== are not valid in R, and =! is incorrect syntax.

3. Final Answer:

   x != 10 -> Option A

4. Quick Check:

   Not equal operator = != [OK]

Hint: Use != to check inequality in R [OK]

Common Mistakes:

• Using <> which is invalid in R
• Writing =! instead of !=
• Using !== which is from other languages

3. What is the output of the following R code?

x <- 5
y <- 7
x > y

medium

A. FALSE

B. TRUE

C. 5

D. Error

Solution

1. Step 1: Compare values of x and y

   x is 5 and y is 7, so 5 > 7 is being checked.

2. Step 2: Evaluate the comparison

   Since 5 is not greater than 7, the expression returns FALSE.

3. Final Answer:

   FALSE -> Option A

4. Quick Check:

   5 > 7 = FALSE [OK]

Hint: Compare numbers directly; 5 > 7 is false [OK]

Common Mistakes:

• Confusing > with <
• Expecting numeric output instead of logical
• Thinking it causes an error

4. Identify the error in this R code snippet:

if (x = 10) { print("Yes") }

medium

A. No error, code is correct

B. Missing curly braces

C. Using = instead of ==

D. print() is incorrect function

Solution

1. Step 1: Check the condition syntax in if statement

   In R, to compare values, use ==, not =.

2. Step 2: Understand the difference between assignment and comparison

   = assigns a value, but == tests equality. Using = in if condition causes an error or unexpected behavior.

3. Final Answer:

   Using = instead of == -> Option C

4. Quick Check:

   Comparison needs ==, not = [OK]

Hint: Use == for comparison inside if() [OK]

Common Mistakes:

• Using = instead of ==
• Ignoring syntax errors from wrong operator
• Thinking = works for comparison

5. You want to filter a vector v <- c(3, 5, 7, 9) to keep only values greater than or equal to 5. Which R expression correctly uses comparison operators to do this?

hard

A. v[v => 5]

B. v[v >= 5]

C. v[v = 5]

D. v[v >== 5]

Solution

1. Step 1: Understand filtering with comparison

   To keep values >= 5, use the operator >= inside the indexing brackets.

2. Step 2: Check syntax correctness

   =>, =, and >== are invalid operators in R.

3. Final Answer:

   v[v >= 5] -> Option B

4. Quick Check:

   Use >= for greater or equal in filtering [OK]

Hint: Use >= for greater or equal comparisons [OK]

Common Mistakes:

• Using => which is invalid
• Using = instead of comparison operator
• Combining > and == incorrectly