Numeric and character vectors in R Programming - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of combining numeric and character vectors

What is the output of this R code when combining numeric and character vectors?

R Programming

v1 <- c(1, 2, 3)
v2 <- c("a", "b", "c")
v3 <- c(v1, v2)
print(v3)

A [1] "1" "2" "3" "a" "b" "c"

B [1] 1 2 3 "a" "b" "c"

C [1] 1 2 3 NA NA NA

D [1] 1 2 3 4 5 6

💡 Hint

Remember that combining numeric and character vectors converts all elements to characters.

When you combine numeric and character vectors in R, all elements are coerced to character type. So the numeric values become strings.

❓ Predict Output

intermediate

Length of a mixed vector

What is the length of the vector created by this code?

R Programming

v1 <- c(10, 20, 30)
v2 <- c("x", "y")
v3 <- c(v1, v2)
length(v3)

A NA

B 3

C 2

D 5

💡 Hint

The length counts all elements after combining.

The vector v3 combines 3 numeric and 2 character elements, so length is 5.

🔧 Debug

advanced

Error in vector creation with mixed types

What error does this R code produce?

R Programming

v <- c(1, "two", TRUE, 4.5)
print(v)

A No error; prints a character vector: "1" "two" "TRUE" "4.5"

B Error: unexpected string constant

C Error: cannot combine numeric and logical values

D No error; prints a numeric vector: 1 0 1 4.5

💡 Hint

Check how R coerces different types in a vector.

R coerces all elements to the most flexible type, here character, so no error occurs.

🧠 Conceptual

advanced

Understanding vector coercion priority

Which type will the vector have after combining these elements: numeric, logical, and character?

A Numeric

B Character

C Logical

D Factor

💡 Hint

R coerces to the most flexible type to hold all values.

Character is the most flexible type among logical, numeric, and character, so all elements become characters.

❓ Predict Output

expert

Output of vector recycling in arithmetic

What is the output of this R code?

R Programming

v1 <- c(1, 2, 3, 4)
v2 <- c(10, 20)
v3 <- v1 + v2
print(v3)

A Error: vectors must be the same length

B [1] 11 22 31 42

C [1] 11 22 13 24

D [1] 11 22 11 22

💡 Hint

Remember how R recycles shorter vectors in arithmetic operations.

v2 is recycled to match length of v1: (10,20,10,20). Adding element-wise gives (11,22,13,24).

Practice

1. Which of the following correctly creates a numeric vector in R?

easy

A. c(TRUE, FALSE, TRUE)

B. c("one", "two", "three")

C. c(1, "two", 3)

D. c(1, 2, 3, 4)

Solution

1. Step 1: Understand numeric vector creation

   Numeric vectors contain only numbers, so elements must be numeric values.

2. Step 2: Check each option's elements

   c(1, 2, 3, 4) has only numbers, so it is a numeric vector. c("one", "two", "three") has text, c(TRUE, FALSE, TRUE) has logical values, and c(1, "two", 3) mixes numbers and text, which converts all to characters.

3. Final Answer:

   c(1, 2, 3, 4) -> Option D

4. Quick Check:

   Numeric vector = c(1, 2, 3, 4) [OK]

Hint: Numeric vectors contain only numbers inside c() [OK]

Common Mistakes:

• Mixing numbers and text creates character vector
• Confusing logical vectors with numeric
• Using quotes around numbers

2. Which of these is the correct syntax to create a character vector in R?

easy

A. c(1, 2, 3)

B. c("apple", "banana", "cherry")

C. c(TRUE, FALSE, TRUE)

D. c(1, "banana", 3)

Solution

1. Step 1: Identify character vector syntax

   Character vectors contain text strings, which must be inside quotes.

2. Step 2: Check options for quoted text

   c("apple", "banana", "cherry") has all elements as quoted text strings, so it is a character vector. c(1, 2, 3) is numeric, c(TRUE, FALSE, TRUE) is logical, and c(1, "banana", 3) mixes types causing coercion.

3. Final Answer:

   c("apple", "banana", "cherry") -> Option B

4. Quick Check:

   Character vector = c("apple", "banana", "cherry") [OK]

Hint: Use quotes around text to create character vectors [OK]

Common Mistakes:

• Forgetting quotes around text
• Mixing types in one vector
• Using numbers without quotes for text

3. What is the output of this R code?

x <- c(5, 10, 15)
y <- c("a", "b", "c")
z <- c(x, y)
print(z)

medium

A. [1] "5" "10" "15" "a" "b" "c"

B. [1] 5 10 15 "a" "b" "c"

C. [1] 5 10 15 NA NA NA

D. Error: cannot combine numeric and character vectors

Solution

1. Step 1: Understand vector combining rules in R

   When combining numeric and character vectors, R converts all elements to character to keep the same type.

2. Step 2: Analyze the combined vector z

   Vector z contains numbers 5, 10, 15 and characters "a", "b", "c". All numbers become strings, so print shows all as character strings.

3. Final Answer:

   [1] "5" "10" "15" "a" "b" "c" -> Option A

4. Quick Check:

   Mixed vector coerces to character = [1] "5" "10" "15" "a" "b" "c" [OK]

Hint: Mixed types in vector become character strings [OK]

Common Mistakes:

• Expecting numeric values to stay numeric
• Thinking R throws error on combining types
• Assuming NA values appear for mismatched types

4. Identify the error in this R code:

vec <- c(1, 2, "three", 4)
sum(vec)

medium

A. No error; sum returns 10

B. sum() returns NA due to mixed types

C. Error because sum() cannot handle character vectors

D. Error because c() cannot mix numbers and text

Solution

1. Step 1: Understand vector creation with mixed types

   c(1, 2, "three", 4) creates a character vector because of the text element "three".

2. Step 2: Check sum() behavior on character vectors

   sum() expects numeric input. Passing a character vector causes an error because it cannot sum text.

3. Final Answer:

   Error because sum() cannot handle character vectors -> Option C

4. Quick Check:

   sum(character vector) = Error [OK]

Hint: sum() needs numeric vectors, not characters [OK]

Common Mistakes:

• Assuming sum() converts characters to numbers
• Thinking c() forbids mixing types (it coerces instead)
• Expecting sum() to return NA silently

5. You have two vectors:

nums <- c(2, 4, 6, 8)
chars <- c("2", "4", "6", "8")

How can you create a numeric vector from chars and add it to nums element-wise?

hard

A. nums + as.numeric(chars)

B. nums + chars

C. as.character(nums) + chars

D. sum(nums, chars)

Solution

1. Step 1: Convert character vector to numeric

   Use as.numeric(chars) to change text numbers to numeric values.

2. Step 2: Add numeric vectors element-wise

   Adding nums + as.numeric(chars) adds corresponding elements correctly.

3. Final Answer:

   nums + as.numeric(chars) -> Option A

4. Quick Check:

   Convert chars to numeric before adding = nums + as.numeric(chars) [OK]

Hint: Convert text to numbers with as.numeric() before math [OK]

Common Mistakes:

• Adding numeric and character vectors directly
• Using sum() instead of element-wise addition
• Converting numeric to character instead of chars to numeric