nchar and substring in R Programming - Mini Project: Build & Apply

Using nchar and substring in R

📖 Scenario: You work in a library and have a list of book titles. You want to find out how long each title is and extract a part of each title to create short labels.

🎯 Goal: Build a small R program that calculates the length of each book title using nchar and extracts the first 5 characters of each title using substring.

📋 What You'll Learn

Create a vector called book_titles with exactly these titles: "Data Science Basics", "R Programming", "Statistics 101"

Create a variable called title_lengths that stores the length of each title using nchar

Create a variable called short_labels that stores the first 5 characters of each title using substring

Print the title_lengths and short_labels variables

💡 Why This Matters

🌍 Real World

Libraries, bookstores, or any place with lists of names or titles often need to measure string lengths and create short labels for display.

💼 Career

Knowing how to manipulate strings is essential for data cleaning, reporting, and user interface design in many programming and data analysis jobs.

1

Create the book titles vector

Create a vector called book_titles with these exact strings: "Data Science Basics", "R Programming", "Statistics 101"

R Programming

# Create the vector book_titles with the given titles
# Your code here

Hint

Use the c() function to create a vector with the exact titles.

2

Calculate the length of each title

Create a variable called title_lengths that stores the length of each title in book_titles using the nchar function

R Programming

book_titles <- c("Data Science Basics", "R Programming", "Statistics 101")
# Calculate the length of each title using nchar and store in title_lengths
# Your code here

Hint

Use nchar(book_titles) to get the length of each string in the vector.

3

Extract the first 5 characters of each title

Create a variable called short_labels that stores the first 5 characters of each title in book_titles using the substring function

R Programming

book_titles <- c("Data Science Basics", "R Programming", "Statistics 101")
title_lengths <- nchar(book_titles)
# Extract first 5 characters of each title using substring and store in short_labels
# Your code here

Hint

Use substring(book_titles, 1, 5) to get the first 5 characters of each string.

4

Print the results

Print the variables title_lengths and short_labels to display the lengths and short labels of the book titles

R Programming

book_titles <- c("Data Science Basics", "R Programming", "Statistics 101")
title_lengths <- nchar(book_titles)
short_labels <- substring(book_titles, 1, 5)
# Print title_lengths and short_labels
# Your code here

Hint

Use print(title_lengths) and print(short_labels) to show the results.

Practice

1. What does the nchar function do in R?

easy

A. Returns the number of characters in a string

B. Extracts a substring from a string

C. Converts a string to uppercase

D. Counts the number of words in a string

Solution

1. Step 1: Understand the purpose of nchar

   The nchar function counts how many characters are in a string, including spaces and punctuation.

2. Step 2: Compare with other options

   Other options describe different functions: substring extracts parts, toupper converts case, and word count is not done by nchar.

3. Final Answer:

   Returns the number of characters in a string -> Option A

4. Quick Check:

   nchar("hello") = 5 [OK]

Hint: Remember: nchar counts characters, substring extracts parts [OK]

Common Mistakes:

• Confusing nchar with substring
• Thinking nchar counts words
• Assuming nchar changes the string

2. Which of the following is the correct way to extract the substring "cat" from the string "concatenate" in R?

easy

A. substring("concatenate", 3, 5)

B. substring("concatenate", 4, 6)

C. substring("concatenate", 5, 7)

D. substring("concatenate", 2, 4)

Solution

1. Step 1: Identify the position of "cat" in "concatenate"

   "concatenate" is c(1)o(2)n(3)c(4)a(5)t(6)e(7)n(8)a(9)t(10)e(11). The substring "cat" starts at position 4 and ends at 6.

2. Step 2: Use substring with correct start and end

   Using substring("concatenate", 4, 6) extracts characters 4 to 6, which is "cat".

3. Final Answer:

   substring("concatenate", 4, 6) -> Option B

4. Quick Check:

   substring("concatenate", 4, 6) = "cat" [OK]

Hint: Count characters starting at 1 to find substring positions [OK]

Common Mistakes:

• Starting count at 0 instead of 1
• Mixing up start and end positions
• Using incorrect substring indices

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

text <- "Programming"
len <- nchar(text)
sub <- substring(text, 4, 7)
print(len)
print(sub)

medium

A. 11 and "gram"

B. 11 and "gramm"

C. 10 and "gram"

D. 10 and "gramm"

Solution

1. Step 1: Calculate length of "Programming" using nchar

   "Programming" has 11 characters: P(1) r(2) o(3) g(4) r(5) a(6) m(7) m(8) i(9) n(10) g(11). So, len = 11.

2. Step 2: Extract substring from position 4 to 7

   Characters 4 to 7 are g(4) r(5) a(6) m(7), so substring is "gram".

3. Final Answer:

   11 and "gram" -> Option A

4. Quick Check:

   nchar("Programming") = 11, substring(4,7) = "gram" [OK]

Hint: Count characters carefully; substring includes both start and end [OK]

Common Mistakes:

• Counting length as 10 instead of 11
• Extracting one extra character in substring
• Confusing substring end position as exclusive

4. The following code is intended to extract "data" from the string "database" but it gives wrong output. What is the error?

text <- "database"
result <- substring(text, 1, 3)
print(result)

medium

A. The string variable is misspelled

B. substring function syntax is wrong

C. nchar should be used instead of substring

D. Start and end positions are incorrect; should be 1 to 4

Solution

1. Step 1: Check the substring positions used

   substring(text, 1, 3) extracts characters 1 to 3: "dat" from "database".

2. Step 2: Identify correct positions for "data"

   "data" is characters 1 to 4, so end position should be 4, not 3.

3. Final Answer:

   Start and end positions are incorrect; should be 1 to 4 -> Option D

4. Quick Check:

   substring("database", 1, 4) = "data" [OK]

Hint: Remember substring end position is inclusive [OK]

Common Mistakes:

• Using end position one less than needed
• Confusing substring with nchar usage
• Assuming substring excludes end position

5. You have a vector of strings: words <- c("apple", "banana", "cherry"). Write R code using substring and nchar to create a new vector containing the last 3 characters of each word. Which code snippet does this correctly?

hard

A. substring(words, nchar(words), nchar(words)+2)

B. substring(words, 1, 3)

C. substring(words, nchar(words)-2, nchar(words))

D. substring(words, nchar(words)-3, nchar(words)-1)

Solution

1. Step 1: Understand how to get last 3 characters

   For each word, last 3 characters start at position (length - 2) and end at length. Use nchar(words) to get length.

2. Step 2: Use substring with vectorized start and end

   substring(words, nchar(words)-2, nchar(words)) extracts last 3 characters for each word correctly.

3. Step 3: Check other options

   substring(words, 1, 3) extracts first 3 characters, C uses invalid end position, D extracts wrong positions.

4. Final Answer:

   substring(words, nchar(words)-2, nchar(words)) -> Option C

5. Quick Check:

   Last 3 chars of "banana" = "ana" [OK]

Hint: Use nchar(word)-2 as start for last 3 chars [OK]

Common Mistakes:

• Using fixed start positions instead of dynamic
• Off-by-one errors in start or end positions
• Assuming substring end is exclusive