Vector arithmetic (element-wise) in R Programming - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this vector addition?

Consider the following R code that adds two vectors element-wise. What is the output?

R Programming

v1 <- c(2, 4, 6)
v2 <- c(1, 3, 5)
v_sum <- v1 + v2
print(v_sum)

A [1] 3 7 9

B [1] 3 7 11

C [1] 3 7 10

D [1] 3 7 12

💡 Hint

Add each element of v1 to the corresponding element of v2.

Element-wise addition sums each pair of elements: 2+1=3, 4+3=7, 6+5=11. The correct sum is 3, 7, 11.

❓ Predict Output

intermediate

What is the output of this vector multiplication?

What will this R code print when multiplying two vectors element-wise?

R Programming

a <- c(3, 0, 2)
b <- c(4, 5, 6)
result <- a * b
print(result)

A [1] 12 0 12

B [1] 7 5 8

C [1] 12 5 12

D [1] 3 0 2

💡 Hint

Multiply each element of 'a' by the corresponding element of 'b'.

Element-wise multiplication: 3*4=12, 0*5=0, 2*6=12.

🔧 Debug

advanced

Why does this vector subtraction code produce a warning?

Examine the code below. Why does R give a warning when subtracting these vectors?

R Programming

x <- c(10, 20, 30, 40, 50)
y <- c(1, 2)
z <- x - y
print(z)

A Because x and y must be the same length or R throws an error.

B Because subtraction is not allowed between vectors in R.

C Because y is not numeric.

D Because vectors have different lengths and R recycles elements with a warning.

💡 Hint

Check the lengths of the vectors and how R handles recycling.

R recycles the shorter vector y to match the length of x but warns if the longer vector length is not a multiple of the shorter one.

❓ Predict Output

advanced

What is the output of this vector division with recycling?

What will this R code print when dividing vectors of different lengths?

R Programming

v1 <- c(8, 16, 24, 32, 40)
v2 <- c(2, 4)
result <- v1 / v2
print(result)

A [1] 4 4 12 8 20

B [1] 4 4 12 8 20 # no warning

C [1] 4 4 12 8 20 # with warning

D [1] 4 4 6 8 10

💡 Hint

Remember how R recycles the shorter vector to match the longer one.

v2 is recycled as (2,4,2,4,2). Division: 8/2=4, 16/4=4, 24/2=12, 32/4=8, 40/2=20. A warning occurs because 5 is not a multiple of 2; R warns when the length of the longer vector is not a multiple of the shorter vector.

❓ Predict Output

expert

What is the value of 'result' after this complex vector operation?

Given the code below, what is the value of the variable 'result'?

R Programming

v <- c(1, 2, 3, 4, 5)
result <- (v * 2) - (v %% 2) + c(5, 4, 3, 2, 1)
print(result)

A [1] 6 8 8 10 10

B [1] 6 8 9 10 11

C [1] 6 7 9 10 11

D [1] 6 7 8 10 11

💡 Hint

Calculate each part step-by-step: multiply, modulo, then add.

Step 1: v*2 = c(2,4,6,8,10) Step 2: v%%2 = c(1,0,1,0,1) Step 3: (v*2) - (v%%2) = c(1,4,5,8,9) Step 4: + c(5,4,3,2,1) = c(6,8,8,10,10)