Named vectors in R Programming - Mini Project: Build & Apply

Named vectors

📖 Scenario: Imagine you are organizing a small fruit basket. You want to keep track of the number of each fruit you have, and give each count a name so you can easily find it later.

🎯 Goal: You will create a named vector in R where each fruit name is linked to its quantity. Then, you will access and display this information.

📋 What You'll Learn

Create a numeric vector with exact quantities for fruits

Assign names to each element in the vector matching the fruit names

Access the vector elements by their names

Print the named vector to show the fruit quantities

💡 Why This Matters

🌍 Real World

Named vectors help you label data clearly, like keeping track of items in a basket or inventory.

💼 Career

Understanding named vectors is useful in data analysis and programming jobs where you work with labeled data.

1

Create a numeric vector with fruit quantities

Create a numeric vector called fruit_counts with these exact values: 5, 3, 7, 2.

R Programming

# Create a numeric vector called fruit_counts with values 5, 3, 7, 2
# Your code here

Hint

Use the c() function to combine numbers into a vector.

2

Assign names to the vector elements

Assign names "apple", "banana", "orange", and "pear" to the elements of the fruit_counts vector using the names() function.

R Programming

fruit_counts <- c(5, 3, 7, 2)
# Assign names to fruit_counts vector elements
# Your code here

Hint

Use names(fruit_counts) <- c(...) to assign names.

3

Access elements by their names

Create a new variable called apple_count and assign it the value of the fruit_counts element named "apple".

R Programming

fruit_counts <- c(5, 3, 7, 2)
names(fruit_counts) <- c("apple", "banana", "orange", "pear")
# Assign the value of fruit_counts["apple"] to apple_count
# Your code here

Hint

Use fruit_counts["apple"] to get the value for apple.

4

Print the named vector

Print the fruit_counts vector to display the fruit names and their quantities.

R Programming

fruit_counts <- c(5, 3, 7, 2)
names(fruit_counts) <- c("apple", "banana", "orange", "pear")
apple_count <- fruit_counts["apple"]
# Print the fruit_counts vector
# Your code here

Hint

Use print(fruit_counts) to show the named vector.

Practice

1. What is a named vector in R?

easy

A. A vector that only contains numeric values

B. A vector where each element has a name label for easy access

C. A vector that cannot be modified after creation

D. A vector that stores only character strings

Solution

1. Step 1: Understand vector naming

   Named vectors have names assigned to each element, making it easier to access elements by name.

2. Step 2: Compare options

   Only A vector where each element has a name label for easy access correctly describes a named vector as having name labels for elements.

3. Final Answer:

   A vector where each element has a name label for easy access -> Option B

4. Quick Check:

   Named vector = vector with names [OK]

Hint: Named vectors have labels for elements, not just values [OK]

Common Mistakes:

• Thinking named vectors only hold numbers
• Confusing named vectors with immutable vectors
• Assuming named vectors store only strings

2. Which of the following is the correct way to create a named vector in R?

easy

A. c(apple = 5, banana = 3, cherry = 7)

B. vector(apple:5, banana:3, cherry:7)

C. named_vector(5, 3, 7, names = c('apple', 'banana', 'cherry'))

D. c(5 = apple, 3 = banana, 7 = cherry)

Solution

1. Step 1: Recall named vector syntax

   Named vectors are created using c(name = value) pairs.

2. Step 2: Check each option

   c(apple = 5, banana = 3, cherry = 7) uses correct syntax: c(apple = 5, banana = 3, cherry = 7). Others use invalid syntax or functions.

3. Final Answer:

   c(apple = 5, banana = 3, cherry = 7) -> Option A

4. Quick Check:

   Use c(name = value) to create named vectors [OK]

Hint: Use c(name = value) pairs to create named vectors [OK]

Common Mistakes:

• Using colons instead of equals for naming
• Trying to use non-existent functions like named_vector()
• Placing values before names incorrectly

3. What will be the output of the following R code?

fruits <- c(apple = 10, banana = 5, cherry = 8)
fruits["banana"]

medium

A. 5

B. "banana"

C. Error: object not found

D. c(banana = 5)

Solution

1. Step 1: Understand named vector indexing

   Accessing a named vector element by name returns a named vector of length 1 with that element.

2. Step 2: Analyze the code output

   fruits["banana"] returns a named vector with name 'banana' and value 5, shown as c(banana = 5).

3. Final Answer:

   c(banana = 5) -> Option D

4. Quick Check:

   Access by name returns named vector element [OK]

Hint: Accessing by name returns named vector element, not just value [OK]

Common Mistakes:

• Expecting just the value without name
• Confusing output with string name
• Assuming it causes an error

4. Identify the error in the following R code that tries to create a named vector:

numbers <- c(1 = "one", 2 = "two", 3 = "three")

medium

A. Values and names are reversed; names should be strings on the left

B. The syntax uses numbers as names incorrectly; names must be on the left side

C. Numbers cannot be used as names in named vectors

D. The c() function cannot create named vectors

Solution

1. Step 1: Check named vector syntax

   Named vectors use name = value pairs, with names on the left and values on the right.

2. Step 2: Analyze the code

   The code uses numbers on the left and strings on the right, which reverses the expected order.

3. Final Answer:

   Values and names are reversed; names should be strings on the left -> Option A

4. Quick Check:

   Names = values, not values = names [OK]

Hint: Names must be on left side, values on right in c(name = value) [OK]

Common Mistakes:

• Putting values on left and names on right
• Thinking numbers cannot be names (they can as strings)
• Believing c() can't create named vectors

5. Given the named vector temps <- c(Mon = 22, Tue = 25, Wed = 20, Thu = 23), how would you create a new named vector with only days where temperature is above 22?

hard

A. temps[">22"]

B. temps[temps < 22]

C. temps[temps > 22]

D. temps[temps == 22]

Solution

1. Step 1: Understand logical indexing with named vectors

   You can use a logical condition inside square brackets to filter elements.

2. Step 2: Apply condition temps > 22

   temps > 22 returns TRUE for days with temperature above 22, so temps[temps > 22] selects those days.

3. Final Answer:

   temps[temps > 22] -> Option C

4. Quick Check:

   Use logical condition inside brackets to filter named vectors [OK]

Hint: Use temps[temps > value] to filter named vectors by condition [OK]

Common Mistakes:

• Using incorrect comparison operators
• Trying to index by string '>22' which is invalid
• Selecting equal or less than values instead of greater