Why text processing is common in R Programming - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to print the number of words in the text.

R Programming

text <- "Hello world from R"
words <- strsplit(text, [1])[[1]]
print(length(words))

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

A" "

B"."

C","

D"\n"

Attempts:

3 left

💡 Hint

Common Mistakes

Using a comma or period as the separator instead of a space.

Forgetting to use quotes around the separator.

The text is split by spaces to separate words, so the delimiter is a space " ".

2fill in blank

medium

Complete the code to convert all text to lowercase.

R Programming

text <- "Hello World"
lower_text <- [1](text)
print(lower_text)

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

Atolower

Btrimws

Ccapitalize

Dtoupper

Attempts:

3 left

💡 Hint

Common Mistakes

Using toupper() which converts text to uppercase.

Using functions unrelated to case conversion.

tolower() converts all characters in the text to lowercase.

3fill in blank

hard

Fix the error in the code to replace all spaces with underscores.

R Programming

text <- "Hello world from R"
new_text <- gsub([1], "_", text)
print(new_text)

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

A"-"

B"_"

C" "

D"."

Attempts:

3 left

💡 Hint

Common Mistakes

Replacing underscores instead of spaces.

Using the wrong pattern string.

To replace spaces, the pattern to match is a space " ".

4fill in blank

hard

Fill both blanks to create a named vector with word lengths for words longer than 3 characters.

R Programming

words <- c("cat", "elephant", "dog", "giraffe")
lengths <- c([1](words))
names(lengths) <- words
filtered <- lengths[lengths [2] 3]
print(filtered)

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

Anchar

Blength

C>

D<=

Attempts:

3 left

💡 Hint

Common Mistakes

Using length() which returns the number of elements, not characters.

Using the wrong comparison operator.

nchar() gets the length of each word, and we filter lengths greater than 3.

5fill in blank

hard

Fill all three blanks to create a named vector of uppercase words longer than 4 characters.

R Programming

words <- c("apple", "bat", "carrot", "dog")
upper_words <- toupper([1])
lengths <- nchar([2])
result <- upper_words[lengths [3] 4]
print(result)

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

Awords

Bupper_words

C>

D<=

Attempts:

3 left

💡 Hint

Common Mistakes

Using upper_words for length calculation which is already uppercase.

Using the wrong comparison operator.

We convert original words to uppercase, get their lengths, and filter those longer than 4.

Practice

1. Why is text processing commonly used in programming with R?

easy

A. To clean and analyze words and sentences in data

B. To create graphical plots and charts

C. To perform complex mathematical calculations

D. To manage database connections

Solution

1. Step 1: Understand the purpose of text processing

   Text processing helps handle words and sentences, which are common in data analysis.

2. Step 2: Identify the main use in R

   R uses text processing mainly to clean and analyze textual data, not for graphics or math.

3. Final Answer:

   To clean and analyze words and sentences in data -> Option A

4. Quick Check:

   Text processing = cleaning and analyzing text [OK]

Hint: Text processing = working with words and sentences [OK]

Common Mistakes:

• Confusing text processing with plotting
• Thinking text processing is for math calculations
• Mixing text processing with database management

2. Which of the following is the correct way to convert a string to lowercase in R?

easy

A. strtolower("HELLO")

B. lowercase("HELLO")

C. to_lower("HELLO")

D. tolower("HELLO")

Solution

1. Step 1: Recall R's built-in function for lowercase conversion

   R uses the function tolower() to convert strings to lowercase.

2. Step 2: Check the options for correct syntax

   Only tolower("HELLO") matches R's syntax; others are invalid or from other languages.

3. Final Answer:

   tolower("HELLO") -> Option D

4. Quick Check:

   tolower() converts text to lowercase [OK]

Hint: Use tolower() to convert text to lowercase in R [OK]

Common Mistakes:

• Using functions from other languages like strtolower
• Assuming lowercase() or to_lower() exist in R
• Missing parentheses or quotes in function call

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

text <- "Data Science"
words <- strsplit(text, " ")[[1]]
length(words)

medium

A. 1

B. 2

C. 11

D. Error

Solution

1. Step 1: Understand strsplit function

   strsplit splits the string "Data Science" by space " ", resulting in a list with two words: "Data" and "Science".

2. Step 2: Extract the first element and count words

   Using [[1]] extracts the vector of words, and length() counts how many words are in it, which is 2.

3. Final Answer:

   2 -> Option B

4. Quick Check:

   strsplit splits text into words = 2 [OK]

Hint: strsplit splits text into words; length counts them [OK]

Common Mistakes:

• Counting characters instead of words
• Forgetting to extract list element with [[1]]
• Expecting an error due to syntax

4. Identify the error in this R code for replacing 'cat' with 'dog' in a string:

text <- "The cat sat on the mat"
new_text <- replace(text, "cat", "dog")
new_text

medium

A. replace() is not the correct function for string substitution

B. Missing assignment operator <-

C. Incorrect string quotes used

D. No error, code runs fine

Solution

1. Step 1: Check the function used for string replacement

   In R, replace() is for replacing elements in vectors by index, not for string substitution.

2. Step 2: Identify correct function for string substitution

   To replace text inside strings, sub() or gsub() should be used instead of replace().

3. Final Answer:

   replace() is not the correct function for string substitution -> Option A

4. Quick Check:

   Use sub() or gsub() for string replacement [OK]

Hint: Use sub() or gsub() for replacing text, not replace() [OK]

Common Mistakes:

• Using replace() for string substitution
• Assuming replace() works like sub()
• Ignoring function purpose differences

5. You have a vector of sentences:

sentences <- c("R is great", "I love coding", "Data is powerful")

Which R code correctly creates a vector of the first words from each sentence?

hard

A. substr(sentences, 1, 1)

B. strsplit(sentences, " ")[1]

C. sapply(strsplit(sentences, " "), `[`, 1)

D. tolower(sentences)

Solution

1. Step 1: Understand the goal

   We want the first word from each sentence in the vector.

2. Step 2: Analyze each option

   substr(sentences, 1, 1) extracts only the first character, not the first word.
   strsplit(sentences, " ")[1] returns only the first element of the list, not all first words.
   sapply(strsplit(sentences, " "), `[`, 1) uses strsplit to split each sentence by space, then sapply extracts the first word from each split vector correctly.
   tolower(sentences) converts all text to lowercase, unrelated to extracting words.

3. Final Answer:

   sapply(strsplit(sentences, " "), `[`, 1) -> Option C

4. Quick Check:

   Use sapply + strsplit + `[`, 1 to get first words [OK]

Hint: Use sapply with strsplit and `[`, 1 to get first words [OK]

Common Mistakes:

• Using substr() to get words instead of characters
• Taking only first list element instead of all
• Confusing lowercase conversion with word extraction