Character (string) type in R Programming - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a character string variable named greeting with the value "Hello".

R Programming

greeting <- [1]

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

A"Hello"

BHello

C'Hello'

DHello()

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting quotes around the string

Using a function call instead of a string

In R, character strings must be enclosed in double or single quotes. Here, double quotes are used.

2fill in blank

medium

Complete the code to find the number of characters in the string stored in word.

R Programming

length <- [1](word)

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

Acount

Bsize

Clength

Dnchar

Attempts:

3 left

💡 Hint

Common Mistakes

Using length() which counts elements in a vector, not characters in a string

Using undefined functions like count() or size()

The nchar() function returns the number of characters in a string in R.

3fill in blank

hard

Fix the error in the code to concatenate two strings with a space between them.

R Programming

full_name <- paste(first_name, [1], last_name)

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

A""

B' '

C'_'

Dspace

Attempts:

3 left

💡 Hint

Common Mistakes

Using empty quotes which join strings without space

Using an undefined variable like space

To add a space between two strings in paste(), use a string with a space: ' '.

4fill in blank

hard

Fill both blanks to create a named vector with words as names and their lengths as values.

R Programming

word_lengths <- c([1] = nchar([2]))

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

Aword

Bwords

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing singular and plural variable names

Using undefined variables

We use the variable word as the name and calculate its length with nchar(word).

5fill in blank

hard

Fill all three blanks to create a named vector of uppercase words with their lengths greater than 3.

R Programming

result <- c([1] = [2](word), nchar(word)[nchar(word) [3] 3])

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

Aword

Btoupper

C>

Dtolower

Attempts:

3 left

💡 Hint

Common Mistakes

Using tolower() instead of toupper()

Using wrong comparison operators like < or ==

The name is word, the function to uppercase is toupper, and the condition is > 3.

Practice

1. What is the correct way to create a character string in R?

easy

A. Using quotes like "hello"

B. Using parentheses like (hello)

C. Using square brackets like [hello]

D. Using curly braces like {hello}

Solution

1. Step 1: Understand character string syntax in R

   Character strings must be enclosed in quotes, either single or double.

2. Step 2: Identify the correct option

   Only Using quotes like "hello" uses quotes correctly to create a character string.

3. Final Answer:

   Using quotes like "hello" -> Option A

4. Quick Check:

   Character strings = text inside quotes [OK]

Hint: Remember: text strings always go inside quotes [OK]

Common Mistakes:

• Using parentheses instead of quotes
• Forgetting to use quotes around text
• Using brackets or braces which are not for strings

2. Which of the following is the correct syntax to join two strings "Hello" and "World" in R?

easy

A. paste("Hello", "World")

B. join("Hello", "World")

C. concat("Hello", "World")

D. combine("Hello", "World")

Solution

1. Step 1: Recall string joining function in R

   In R, paste() is used to join strings with a space by default.

2. Step 2: Check the options

   Only paste("Hello", "World") uses the correct function paste() to join strings.

3. Final Answer:

   paste("Hello", "World") -> Option A

4. Quick Check:

   Use paste() to join strings [OK]

Hint: Use paste() to combine strings with spaces [OK]

Common Mistakes:

• Using non-existent functions like join or concat
• Forgetting quotes around strings
• Using functions that do not exist in base R

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

text <- "R is fun"
substr(text, 1, 3)

medium

A. "R is fun"

B. "R i"

C. "R is"

D. "is f"

Solution

1. Step 1: Understand substr() function

   substr(text, start, stop) extracts substring from position start to stop inclusive.

2. Step 2: Apply to given code

   Positions 1 to 3 in "R is fun" are "R", " ", and "i" which combine to "R i" but note the space is counted as a character.

3. Step 3: Check actual substring

   Positions 1 to 3 are characters: 'R' (1), ' ' (2), 'i' (3), so substring is "R i".

4. Final Answer:

   "R i" -> Option B

5. Quick Check:

   substr() extracts characters by position [OK]

Hint: Count characters including spaces for substr() [OK]

Common Mistakes:

• Ignoring spaces as characters
• Confusing substr() with substring() behavior
• Off-by-one errors in positions

4. Identify the error in this R code that tries to create a character vector:

words <- c(hello, "world", "R")

medium

A. Extra comma after hello

B. Using c() instead of paste()

C. Wrong function name, should be concat()

D. Missing quotes around hello

Solution

1. Step 1: Check each element in the vector

   All elements must be character strings with quotes, but hello is unquoted.

2. Step 2: Identify the error

   Missing quotes around hello causes R to look for a variable named hello, which likely does not exist.

3. Final Answer:

   Missing quotes around hello -> Option D

4. Quick Check:

   Character strings need quotes [OK]

Hint: Always quote text inside c() for character vectors [OK]

Common Mistakes:

• Forgetting quotes around text
• Confusing c() with paste() for vectors
• Assuming c() concatenates strings without quotes

5. You have a vector of words c("apple", "banana", "cherry"). How do you create a single character string with these words separated by commas and a space, like "apple, banana, cherry"?

hard

A. paste0(c("apple", "banana", "cherry"), collapse=",")

B. paste(c("apple", "banana", "cherry"), sep=",")

C. paste(c("apple", "banana", "cherry"), collapse=", ")

D. paste0(c("apple", "banana", "cherry"), sep=",")

Solution

1. Step 1: Understand paste() with collapse

   The collapse argument joins vector elements into one string separated by the given string.

2. Step 2: Check the options

   paste(c("apple", "banana", "cherry"), collapse=", ") correctly uses paste() with collapse=", " to join words with comma and space.

3. Step 3: Why not sep?

   sep controls separator between arguments, not vector elements; collapse is needed here.

4. Final Answer:

   paste(c("apple", "banana", "cherry"), collapse=", ") -> Option C

5. Quick Check:

   Use collapse to join vector elements [OK]

Hint: Use collapse in paste() to join vector elements [OK]

Common Mistakes:

• Using sep instead of collapse
• Using paste0 which does not add separators
• Not quoting the separator string