Useful vector functions (length, sum, mean) in R Programming - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this R code using length()?

Consider the vector v <- c(3, 7, 2, 9, 4). What does length(v) return?

R Programming

v <- c(3, 7, 2, 9, 4)
length(v)

A 4

B 9

C 5

D Error: object 'v' not found

💡 Hint

The length() function returns how many elements are in the vector.

The vector v has 5 numbers, so length(v) returns 5.

❓ Predict Output

intermediate

What is the sum of elements in this vector?

Given nums <- c(10, 20, 30, 40), what does sum(nums) return?

R Programming

nums <- c(10, 20, 30, 40)
sum(nums)

A Error: object 'nums' not found

B 40

C 10

D 100

💡 Hint

sum() adds all numbers in the vector.

Adding 10 + 20 + 30 + 40 equals 100, so sum(nums) returns 100.

❓ Predict Output

advanced

What is the mean of this vector with NA values?

Given data <- c(5, NA, 15, 20), what does mean(data, na.rm = TRUE) return?

R Programming

data <- c(5, NA, 15, 20)
mean(data, na.rm = TRUE)

A Error: missing value and na.rm not set to TRUE

B 13.33333

C 15

D NA

💡 Hint

na.rm = TRUE tells mean() to ignore NA values.

Ignoring NA, the mean is (5 + 15 + 20) / 3 = 13.33333.

❓ Predict Output

advanced

What error does this code produce?

What happens when you run sum(c(1, 2, '3')) in R?

R Programming

sum(c(1, 2, '3'))

A 6

B Error: invalid 'type' (character) of argument

C 3

D NA

💡 Hint

sum() expects numeric values, but '3' is a character here.

The vector mixes numbers and a character, so sum() cannot add them and throws a type error.

🧠 Conceptual

expert

How many elements are in the vector after this operation?

If v <- c(1, 2, 3, 4, 5) and then v <- v[-c(2, 4)] is run, what is length(v)?

R Programming

v <- c(1, 2, 3, 4, 5)
v <- v[-c(2, 4)]
length(v)

A 3

B 4

C 2

D 5

💡 Hint

Removing elements 2 and 4 means those positions are gone from the vector.

Removing elements at positions 2 and 4 leaves elements 1, 3, and 5, so length is 3.