Named vectors in R Programming - Step-by-Step Execution

Concept Flow - Named vectors

Create vector values

↓

Assign names to each element

↓

Access elements by name or position

↓

Use named vector in calculations or display

Create a vector, assign names to each element, then access or use elements by their names or positions.

Execution Sample

R Programming

scores <- c(90, 85, 78)
names(scores) <- c("Math", "Science", "English")
scores["Science"]

Create a numeric vector with scores, name each score by subject, then access the Science score by its name.

Execution Table

Step	Action	Vector Content	Names	Access/Output
1	Create vector with values 90, 85, 78	[90, 85, 78]	NULL	Vector created without names
2	Assign names Math, Science, English	[90, 85, 78]	[Math, Science, English]	Names assigned to each element
3	Access element by name 'Science'	[90, 85, 78]	[Math, Science, English]	85
4	Access element by position 1	[90, 85, 78]	[Math, Science, English]	90
5	Print entire named vector	[90, 85, 78]	[Math, Science, English]	Math=90, Science=85, English=78

💡 All steps complete, vector created, named, and accessed successfully

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	Final
scores	NULL	[90, 85, 78]	[90, 85, 78]	[90, 85, 78]	[90, 85, 78] with names Math, Science, English

Key Moments - 3 Insights

Why does the vector have NULL names at first?

At Step 1 in the execution_table, the vector is created without names, so names are NULL until assigned in Step 2.

How can we access elements by name instead of position?

As shown in Step 3, after assigning names, we can use scores["Science"] to get the value 85 by name.

What happens if we try to access a name that does not exist?

Accessing a non-existent name returns NA or an error; this is not shown here but is important to remember.

Visual Quiz - 3 Questions

Look at the execution_table, what is the value of scores after Step 2?

A [85, 78, 90] with names Math, Science, English

B [90, 85, 78] with NULL names

C [90, 85, 78] with names Math, Science, English

D NULL

💡 Hint

Check the Vector Content and Names columns at Step 2 in the execution_table

At which step do we access the element by its name?

A Step 2

B Step 3

C Step 1

D Step 4

💡 Hint

Look for the Access/Output column showing access by name in the execution_table

If we change the name 'Science' to 'Physics', which step's output changes?

A Step 2

B Step 1

C Step 3

D Step 5

💡 Hint

Names are assigned in Step 2, so changing a name affects that step's Names column

Concept Snapshot

Named vectors in R:
- Create vector: c(1,2,3)
- Assign names: names(vec) <- c("a","b","c")
- Access by name: vec["b"]
- Names help identify elements clearly
- Useful for readable code and data

Full Transcript

This visual trace shows how to create a named vector in R. First, a numeric vector is created with values 90, 85, and 78. Initially, the vector has no names. Then, names are assigned to each element: Math, Science, and English. After naming, elements can be accessed by their names, for example, scores["Science"] returns 85. The variable tracker shows the vector's state changes, especially the addition of names. Key moments clarify why names start as NULL and how to access elements by name. The quiz tests understanding of vector content and name assignment steps.

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