Vector arithmetic (element-wise) in R Programming - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to add two vectors element-wise.

R Programming

result <- c(1, 2, 3) [1] c(4, 5, 6)

Drag options to blanks, or click blank then click option'

A*

B-

C/

D+

Attempts:

3 left

💡 Hint

Common Mistakes

Using - instead of + causes subtraction.

In R, the + operator adds vectors element-wise.

2fill in blank

medium

Complete the code to multiply two vectors element-wise.

R Programming

result <- c(2, 4, 6) [1] c(3, 5, 7)

Drag options to blanks, or click blank then click option'

A+

B-

C*

D/

Attempts:

3 left

💡 Hint

Common Mistakes

Using + adds instead of multiplies.

The * operator multiplies vectors element-wise in R.

3fill in blank

hard

Fix the error in the code to subtract vectors element-wise.

R Programming

result <- c(5, 7, 9) [1] c(1, 2, 3)

Drag options to blanks, or click blank then click option'

A*

B-

C+

D/

Attempts:

3 left

💡 Hint

Common Mistakes

Using + adds instead of subtracts.

The - operator subtracts vectors element-wise in R.

4fill in blank

hard

Fill both blanks to divide two vectors element-wise and assign to result.

R Programming

result <- c(10, 20, 30) [1] c(2, 4, 5) [2] 2

Drag options to blanks, or click blank then click option'

A/

B*

C+

D-

Attempts:

3 left

💡 Hint

Common Mistakes

Using + or - instead of division or multiplication.

The / operator divides vectors element-wise. The * operator multiplies the result by 2.

5fill in blank

hard

Fill all three blanks to create a vector of squared differences between two vectors.

R Programming

result <- (c(3, 6, 9) [1] c(1, 2, 3)) [2] [3]

Drag options to blanks, or click blank then click option'

A-

B+

C2

D^

Attempts:

3 left

💡 Hint

Common Mistakes

Using + instead of subtraction.

Using * instead of exponentiation.

Subtract vectors element-wise with -, then raise to the power ^ of 2 to square the differences.

Practice

1.

What happens when you add two vectors of the same length in R, like c(1, 2, 3) + c(4, 5, 6)?

easy

A. The vectors are concatenated into one longer vector.

B. Only the first elements are added, the rest are ignored.

C. Each element in the first vector is added to the corresponding element in the second vector.

D. An error occurs because vectors cannot be added.

Solution

1. Step 1: Understand element-wise addition

   In R, adding two vectors of the same length adds each element from the first vector to the matching element in the second vector.

2. Step 2: Apply addition to given vectors

   Adding c(1, 2, 3) and c(4, 5, 6) results in c(1+4, 2+5, 3+6) which is c(5, 7, 9).

3. Final Answer:

   Each element in the first vector is added to the corresponding element in the second vector. -> Option C

4. Quick Check:

   Element-wise addition = Each element in the first vector is added to the corresponding element in the second vector. [OK]

Hint: Add vectors element by element when lengths match [OK]

Common Mistakes:

• Thinking vectors concatenate instead of adding
• Assuming only first elements add
• Expecting an error for vector addition

2.

Which of the following is the correct syntax to subtract two vectors a and b element-wise in R?

easy

A. subtract_vectors(a, b)

B. subtract(a, b)

C. a %minus% b

D. a - b

Solution

1. Step 1: Recall vector subtraction syntax in R

   In R, element-wise subtraction of vectors uses the minus operator - directly between vectors.

2. Step 2: Verify given options

   Only a - b is valid R syntax for element-wise subtraction. The other options are not built-in R functions or operators.

3. Final Answer:

   a - b -> Option D

4. Quick Check:

   Use - operator for vector subtraction [OK]

Hint: Use '-' operator directly between vectors [OK]

Common Mistakes:

• Using non-existent functions like subtract()
• Trying special operators like %minus%
• Confusing subtraction with other functions

3.

What is the output of the following R code?

v1 <- c(2, 4, 6)
v2 <- c(1, 3, 5)
result <- v1 * v2
print(result)

medium

A. [1] 2 4 6 1 3 5

B. [1] 2 12 30

C. [1] 2 7 11

D. [1] 3 7 11

Solution

1. Step 1: Understand element-wise multiplication

   In R, multiplying two vectors multiplies each element of the first vector by the corresponding element of the second vector.

2. Step 2: Calculate each product

   Multiply elements: 2*1=2, 4*3=12, 6*5=30. So the result is c(2, 12, 30).

3. Final Answer:

   [1] 2 12 30 -> Option B

4. Quick Check:

   Element-wise multiplication = [1] 2 12 30 [OK]

Hint: Multiply vectors element by element for correct output [OK]

Common Mistakes:

• Adding instead of multiplying
• Concatenating vectors instead of multiplying
• Getting sums instead of products

4.

Consider this R code snippet:

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

What is the issue with this code?

medium

A. Vectors have different lengths causing recycling warning.

B. Syntax error due to missing operator.

C. Result will be NULL because vectors differ in length.

D. No issue; code runs correctly without warnings.

Solution

1. Step 1: Check vector lengths

   Vector v1 has length 3, v2 has length 2. They differ in length.

2. Step 2: Understand recycling in R

   R recycles the shorter vector to match the longer one but gives a warning if lengths are not multiples. Here, 3 is not a multiple of 2, so a warning occurs.

3. Final Answer:

   Vectors have different lengths causing recycling warning. -> Option A

4. Quick Check:

   Unequal vector lengths cause recycling warning [OK]

Hint: Vectors must be same length or multiples to avoid warnings [OK]

Common Mistakes:

• Ignoring recycling warnings
• Expecting syntax errors for length mismatch
• Assuming result is NULL when lengths differ

5.

You have two vectors representing daily sales for two stores:
store1 <- c(10, 20, 30, 40)
store2 <- c(5, 15, 25, 35)
How do you calculate the total sales per day for both stores combined using vector arithmetic?

hard

A. total_sales <- store1 + store2

B. total_sales <- store1 * store2

C. total_sales <- store1 - store2

D. total_sales <- c(store1, store2)

Solution

1. Step 1: Understand the goal

   We want total sales per day, so we add sales from both stores for each day.

2. Step 2: Use element-wise addition

   Adding store1 and store2 element-wise sums daily sales: c(10+5, 20+15, 30+25, 40+35) = c(15, 35, 55, 75).

3. Final Answer:

   total_sales <- store1 + store2 -> Option A

4. Quick Check:

   Add vectors element-wise for daily totals [OK]

Hint: Add vectors to combine daily sales totals [OK]

Common Mistakes:

• Multiplying instead of adding sales
• Subtracting sales mistakenly
• Concatenating vectors instead of adding