Named vectors in R Programming - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a named vector with names 'a', 'b', 'c'.

R Programming

vec <- c(1, 2, 3)
names(vec) <- [1]

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

Ac(a, b, c)

Blist('a', 'b', 'c')

Cc('a', 'b', 'c')

Dc("a", "b")

Attempts:

3 left

💡 Hint

Common Mistakes

Using list() instead of c() for names.

Not using quotes around names.

Assigning fewer names than vector elements.

Use c('a', 'b', 'c') to assign names to the vector elements.

2fill in blank

medium

Complete the code to access the element named 'b' from the named vector.

R Programming

vec <- c(x=10, y=20, b=30)
value <- vec[[1]]

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

A"b"

B2

Cb

D3

Attempts:

3 left

💡 Hint

Common Mistakes

Using the name without quotes.

Using the wrong index number.

Confusing names with variable names.

Use the name in quotes to access the element by name: vec["b"].

3fill in blank

hard

Fix the error in the code to correctly assign names to the vector.

R Programming

vec <- c(5, 10, 15)
names(vec) <- [1]

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

Ac(1, 2, 3)

Bc('one', 'two')

Clist('a', 'b', 'c')

Dc('first', 'second', 'third')

Attempts:

3 left

💡 Hint

Common Mistakes

Assigning fewer names than vector elements.

Using numeric vectors instead of character vectors for names.

Using list() instead of c() for names.

The names vector must have the same length as vec. Here, c('first', 'second', 'third') matches length 3.

4fill in blank

hard

Fill both blanks to create a named vector and access the element named 'green'.

R Programming

colors <- c([1])
names(colors) <- c('red', 'green', 'blue')
value <- colors[[2]]

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

A5, 10, 15

B"green"

C"red"

Dc(5, 10, 15)

Attempts:

3 left

💡 Hint

Common Mistakes

Not using c() to create the vector.

Accessing element without quotes.

Using wrong names for access.

Use c(5, 10, 15) to create the vector and "green" to access the named element.

5fill in blank

hard

Fill all three blanks to create a named vector, assign names, and access the element named 'second'.

R Programming

vals <- [1]
names(vals) <- [2]
result <- vals[[3]]

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

Ac(100, 200, 300)

Bc('first', 'second', 'third')

C"second"

Dlist(100, 200, 300)

Attempts:

3 left

💡 Hint

Common Mistakes

Using list() instead of c() for vectors.

Assigning names with wrong length.

Accessing elements without quotes.

Create the vector with c(100, 200, 300), assign names with c('first', 'second', 'third'), and access the element named "second".

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