String formatting with sprintf in R Programming - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to format the number 5 as a string using sprintf.

R Programming

result <- sprintf([1], 5)

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

A"%d"

B"%f"

C"%s"

D"%x"

Attempts:

3 left

💡 Hint

Common Mistakes

Using "%f" formats as floating point with decimals.

Using "%s" expects a string input, not a number.

Using "%x" formats as hexadecimal.

The "%d" format specifier formats the number as an integer string.

2fill in blank

medium

Complete the code to format the number 3.14159 to two decimal places using sprintf.

R Programming

result <- sprintf([1], 3.14159)

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

A"%.2f"

B"%.0f"

C"%.3f"

D"%d"

Attempts:

3 left

💡 Hint

Common Mistakes

Using "%d" truncates the number to integer.

Using "%.0f" rounds to zero decimals.

Using "%.3f" keeps three decimals, not two.

The "%.2f" format specifier formats the number with two decimal places.

3fill in blank

hard

Fix the error in the code to format the string with a name and age using sprintf.

R Programming

result <- sprintf("Name: %s, Age: [1]", "Alice", 30)

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

A"%c"

B"%f"

C"%s"

D"%d"

Attempts:

3 left

💡 Hint

Common Mistakes

Using "%s" for age causes type mismatch.

Using "%f" formats as floating point.

Using "%c" expects a single character.

The "%d" format specifier is used to format integers like age.

4fill in blank

hard

Fill both blanks to format a floating number with width 8 and 3 decimals using sprintf.

R Programming

result <- sprintf([1], [2])

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

A"%8.3f"

B3.14159

C8.12345

D"%6.2f"

Attempts:

3 left

💡 Hint

Common Mistakes

Using "%6.2f" formats with wrong width and decimals.

Passing a string instead of a number as second argument.

Mixing up width and precision in format.

The format "%8.3f" sets width 8 and 3 decimals; 3.14159 is the number to format.

5fill in blank

hard

Fill all three blanks to format a string with a name left-aligned in width 10 and an integer score padded with zeros to width 4.

R Programming

result <- sprintf([1], [2], [3])

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

A"%-10s %04d"

B"%04d"

C"Alice"

D42

Attempts:

3 left

💡 Hint

Common Mistakes

Using "%10s" right-aligns the string.

Using "%d" does not pad zeros.

Passing numbers as strings causes errors.

Use "%-10s %04d" for left-aligned name width 10 and zero-padded score width 4, "Alice" as name, 42 as score.

Practice

1. What does the sprintf function in R primarily do?

easy

A. It reads data from a file and stores it in a string.

B. It splits a string into a list of words.

C. It converts strings to uppercase letters.

D. It creates a formatted string by inserting values into placeholders.

Solution

1. Step 1: Understand the purpose of sprintf

   The sprintf function formats strings by replacing placeholders with values.

2. Step 2: Compare options with the function's purpose

   Only It creates a formatted string by inserting values into placeholders. describes this behavior correctly; others describe unrelated string operations.

3. Final Answer:

   It creates a formatted string by inserting values into placeholders. -> Option D

4. Quick Check:

   sprintf formats strings = B [OK]

Hint: Remember sprintf builds strings by filling placeholders [OK]

Common Mistakes:

• Confusing sprintf with string splitting functions
• Thinking sprintf changes case of letters
• Assuming sprintf reads files

2. Which of the following is the correct syntax to format an integer using sprintf in R?

easy

A. sprintf("%d", 42)

B. sprintf("%s", 42)

C. sprintf("%f", 42)

D. sprintf("%c", 42)

Solution

1. Step 1: Identify the placeholder for integers

   The placeholder %d is used for integers in sprintf.

2. Step 2: Match the placeholder with the value type

   Since 42 is an integer, %d is correct; %s is for strings, %f for floats, and %c for characters.

3. Final Answer:

   sprintf("%d", 42) -> Option A

4. Quick Check:

   Integer placeholder = %d [OK]

Hint: Use %d for integers, %s for strings, %f for decimals [OK]

Common Mistakes:

• Using %s for numbers instead of %d
• Using %f for integers without decimals
• Confusing %c with integer formatting

3. What is the output of this R code?

sprintf("Name: %s, Age: %d", "Alice", 30)

medium

A. "Name: %s, Age: %d"

B. "Name: Alice, Age: 30"

C. "Name: Alice, Age: %d"

D. "Name: %s, Age: 30"

Solution

1. Step 1: Match placeholders with arguments

   The first placeholder %s is replaced by "Alice" (string), the second %d by 30 (integer).

2. Step 2: Construct the final string

   Replacing placeholders gives "Name: Alice, Age: 30" as the output string.

3. Final Answer:

   "Name: Alice, Age: 30" -> Option B

4. Quick Check:

   Placeholders replaced correctly = A [OK]

Hint: Placeholders %s and %d replaced by arguments in order [OK]

Common Mistakes:

• Not replacing placeholders with values
• Mixing up %s and %d placeholders
• Outputting the format string literally

4. Identify the error in this R code:

sprintf("Value: %d", "ten")

medium

A. Incorrect use of double quotes around the format string.

B. Missing closing parenthesis in sprintf function.

C. Using %d placeholder with a string causes a type mismatch error.

D. No error; code runs correctly.

Solution

1. Step 1: Check placeholder and argument types

   The placeholder %d expects an integer, but "ten" cannot be coerced to a number, resulting in NA and a warning.

2. Step 2: Determine if it causes an error

   The code runs but produces a warning and outputs "Value: NA"; this is a type mismatch issue.

3. Final Answer:

   Using %d placeholder with a string causes a type mismatch error. -> Option C

4. Quick Check:

   Type mismatch warning occurs = A [OK]

Hint: sprintf coerces types, may produce NA and warning [OK]

Common Mistakes:

• Confusing coercion warning with type mismatch error
• Looking for missing parenthesis (it's present)
• Assuming invalid quotes (they're correct)

5. You want to format a floating-point number with exactly 2 decimal places using sprintf. Which code snippet achieves this?

hard

A. sprintf("%.2f", 3.14159)

B. sprintf("%2f", 3.14159)

C. sprintf("%f.2", 3.14159)

D. sprintf("%f", round(3.14159, 2))

Solution

1. Step 1: Understand the format for decimal precision

   The format %.2f tells sprintf to print a float with 2 digits after the decimal point.

2. Step 2: Compare options for correct syntax

   sprintf("%.2f", 3.14159) uses %.2f, which is correct. sprintf("%2f", 3.14159) misses the dot, A has incorrect syntax, and D rounds before formatting but does not guarantee 2 decimals in output.

3. Final Answer:

   sprintf("%.2f", 3.14159) -> Option A

4. Quick Check:

   Use %.2f for 2 decimals [OK]

Hint: Use %.2f to fix two decimal places in sprintf [OK]

Common Mistakes:

• Omitting the dot before precision number
• Using round() but forgetting format specifier
• Incorrect order of precision and type specifier