Named vectors in R Programming - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of named vector indexing

What is the output of this R code snippet?

R Programming

vec <- c(a = 10, b = 20, c = 30)
result <- vec["b"]
print(result)

A c 30

B b 20

C 20

D Error: object 'b' not found

💡 Hint

Remember that named vectors keep their names when indexed by name.

Indexing a named vector by name returns a named vector of length 1, so the output includes the name and the value.

❓ Predict Output

intermediate

Length of named vector after subsetting

What is the length of the vector after this operation?

R Programming

vec <- c(x = 5, y = 15, z = 25)
sub_vec <- vec[c("x", "z")]
length(sub_vec)

A 1

B 3

C 2

D Error: invalid subscript type

💡 Hint

Subsetting by a vector of names returns those elements.

Subsetting by two names returns a vector of length 2 containing those elements.

❓ Predict Output

advanced

Output of modifying named vector elements

What is the output of this code?

R Programming

vec <- c(a = 1, b = 2, c = 3)
vec["b"] <- 10
print(vec)

A

a 1
b 10
c 3

B 1 10 3

C

a 1
b 2
c 3

D Error: cannot assign to a named vector element

💡 Hint

You can assign new values to named vector elements by name.

Assigning to a named element changes its value but keeps the name.

❓ Predict Output

advanced

Result of unnamed indexing on named vector

What will this code print?

R Programming

vec <- c(one = 100, two = 200, three = 300)
print(vec[2])

A one 100

B 200

C Error: subscript out of bounds

D two 200

💡 Hint

Indexing by position returns a named vector element.

Indexing by position returns the element with its name.

❓ Predict Output

expert

Output of combining named vectors with overlapping names

What is the output of this R code?

R Programming

v1 <- c(a = 1, b = 2)
v2 <- c(b = 3, c = 4)
combined <- c(v1, v2)
print(combined)

A

a 1
b 2
b 3
c 4

B

a 1
b 5
c 4

C

a 1
b 3
c 4

D Error: duplicate names not allowed

💡 Hint

Combining vectors concatenates elements and keeps all names, even duplicates.

Concatenating named vectors keeps all elements and names, including duplicates.