Regular expressions in R in R Programming - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to check if the string contains the word 'cat'.

R Programming

grepl([1], "The cat is sleeping")

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

A"cat"

B"dog"

C"bird"

D"fish"

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting to put quotes around the pattern.

Using a word not present in the string.

The grepl function checks if the pattern "cat" is found in the string.

2fill in blank

medium

Complete the code to extract all words starting with 'b' from the string.

R Programming

regmatches(text, gregexpr([1], text))

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A"b"

B"\w+b"

C"b+"

D"\bb\w+"

Attempts:

3 left

💡 Hint

Common Mistakes

Not using word boundary \b.

Using incorrect quantifiers.

The pattern "\bb\w+" matches words starting with 'b'.

3fill in blank

hard

Fix the error in the pattern to match email addresses.

R Programming

grepl([1], email)

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A"[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\\.[a-zA-Z]{2,}"

B"[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+.[a-zA-Z]{2,}"

C"[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}"

D"[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\\.[a-zA-Z]{2}"

Attempts:

3 left

💡 Hint

Common Mistakes

Not escaping the dot correctly.

Using single backslash instead of double.

In R strings, a single backslash must be escaped with another backslash. So to match a literal dot, use \\. in the regex, which becomes \. in the string. Option C correctly escapes it.

4fill in blank

hard

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

R Programming

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

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Awords

Bword

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping the names and values.

Using the wrong variable names.

The c() function creates a named vector. The name is each word and the value is the length of each words element.

5fill in blank

hard

Fill all three blanks to create a list of words longer than 4 letters with their uppercase versions.

R Programming

result <- list([1] = [2], [3] = toupper([2]))

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Along_words

Bwords

Attempts:

3 left

💡 Hint

Common Mistakes

Using different variable names inconsistently.

Mixing up the names of list elements.

The list has two elements: long_words holding the words, and long_words holding their uppercase forms. The variable holding the words is words.