String formatting (sprintf) in MATLAB - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to format the number 10 as a string using sprintf.

MATLAB

str = sprintf([1], 10);

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

A'%d'

B'%s'

C'10'

D'%f'

Attempts:

3 left

💡 Hint

Common Mistakes

Using '%s' which is for strings, not numbers.

Putting the number directly as a string instead of using a format specifier.

The '%d' format specifier tells sprintf to format the number as an integer.

2fill in blank

medium

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

MATLAB

str = sprintf([1], 3.14159);

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

A'%s'

B'%.2f'

C'%d'

D'%e'

Attempts:

3 left

💡 Hint

Common Mistakes

Using '%d' which formats as integer and loses decimals.

Using '%e' which formats in exponential notation.

The '%.2f' format specifier formats the number as a floating-point with 2 decimal places.

3fill in blank

hard

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

MATLAB

str = sprintf('Name: %s, Age: [1]', 'Alice', 30);

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

A%d

B%s

C%f

D%c

Attempts:

3 left

💡 Hint

Common Mistakes

Using '%s' which expects a string, causing a mismatch.

Using '%f' which formats floating-point numbers.

The '%d' specifier is used to format the integer age correctly.

4fill in blank

hard

Fill both blanks to format a floating number with 3 decimals and a string.

MATLAB

str = sprintf('Value: [1], Status: [2]', 12.34567, 'OK');

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

A%.3f

B%d

C%s

D%e

Attempts:

3 left

💡 Hint

Common Mistakes

Using '%d' for the floating number, which truncates decimals.

Using '%f' without precision, showing too many decimals.

'%.3f' formats the number with 3 decimals, and '%s' formats the string.

5fill in blank

hard

Fill all three blanks to format a string with a name, integer age, and floating-point score with 1 decimal.

MATLAB

str = sprintf('Name: [1], Age: [2], Score: [3]', 'Bob', 25, 88.765);

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

A%s

B%d

C%.1f

D%f

Attempts:

3 left

💡 Hint

Common Mistakes

Using '%f' without precision for the score.

Using '%s' for the age, causing type mismatch.

'%s' formats the name string, '%d' formats the integer age, and '%.1f' formats the score with one decimal place.

Practice

1. What does the sprintf function in MATLAB do?

easy

A. Creates a formatted string by inserting values into a template

B. Reads input from the user

C. Plots data on a graph

D. Saves variables to a file

Solution

1. Step 1: Understand the purpose of sprintf

   sprintf is used to create text with values inserted in a specific format.

2. Step 2: Compare options to function behavior

   Only Creates a formatted string by inserting values into a template describes creating formatted strings, which matches sprintf's role.

3. Final Answer:

   Creates a formatted string by inserting values into a template -> Option A

4. Quick Check:

   sprintf formats strings = A [OK]

Hint: Remember: sprintf formats text, not input or files [OK]

Common Mistakes:

• Confusing sprintf with input functions
• Thinking sprintf plots graphs
• Assuming sprintf saves files

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

easy

A. str = sprintf('%s', num);

B. str = sprintf('%c', num);

C. str = sprintf('%d', num);

D. str = sprintf('%f', num);

Solution

1. Step 1: Identify format specifier for integers

   The format specifier %d is used for integers in sprintf.

2. Step 2: Match specifier with variable type

   Since num is an integer, %d is correct; others are for strings, floats, or characters.

3. Final Answer:

   str = sprintf('%d', num); -> Option C

4. Quick Check:

   Integer format = %d = D [OK]

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

Common Mistakes:

• Using %s for numbers
• Using %f for integers
• Using %c for non-character data

3. What is the output of the following MATLAB code?

str = sprintf('Value: %0.2f', 3.14159); disp(str);

medium

A. Value: 3.1

B. Value: 3.14

C. Value: 3.14159

D. Value: 03.14

Solution

1. Step 1: Understand the format specifier %0.2f

   This means a floating-point number with 2 digits after the decimal point, padded with zeros if needed.

2. Step 2: Apply formatting to 3.14159

   Rounded to 2 decimals, 3.14159 becomes 3.14, no extra zero padding before the number.

3. Final Answer:

   Value: 3.14 -> Option B

4. Quick Check:

   %.2f rounds float to 2 decimals = Value: 3.14 [OK]

Hint: %.2f rounds float to 2 decimals in sprintf [OK]

Common Mistakes:

• Expecting full decimal without rounding
• Confusing zero padding before decimal
• Ignoring rounding rules

4. Identify the error in this MATLAB code:

str = sprintf('Name: %s, Age: %d', 25, 'John');

medium

A. sprintf cannot format multiple variables

B. Missing semicolon at the end

C. Incorrect format specifier for string

D. The order of variables does not match format specifiers

Solution

1. Step 1: Check format specifiers and variable order

   The format expects a string first (%s) then an integer (%d), but variables are 25 (int) then 'John' (string).

2. Step 2: Identify mismatch cause

   Variables are swapped, causing wrong data types for specifiers.

3. Final Answer:

   The order of variables does not match format specifiers -> Option D

4. Quick Check:

   Variable order must match specifiers = A [OK]

Hint: Match variable order exactly to format specifiers [OK]

Common Mistakes:

• Swapping variable order
• Ignoring type mismatch
• Assuming sprintf auto-corrects order

5. You want to create a formatted string showing a product name and price with 2 decimals, like "Product: Laptop, Price: $999.99". Which sprintf call correctly formats name = 'Laptop' and price = 999.987?

hard

A. sprintf('Product: %s, Price: $%0.2f', name, price)

B. sprintf('Product: %s, Price: $%d', price, name)

C. sprintf('Product: %s, Price: $%f', name, price)

D. sprintf('Product: %s, Price: $%.2d', name, price)

Solution

1. Step 1: Identify correct format specifiers

   %s for string name, %0.2f for float price with 2 decimals.

2. Step 2: Check variable order and formatting

   sprintf('Product: %s, Price: $%0.2f', name, price) uses correct order and formats price to 2 decimals, rounding 999.987 to 999.99.

3. Final Answer:

   sprintf('Product: %s, Price: $%0.2f', name, price) -> Option A

4. Quick Check:

   String + float with 2 decimals = B [OK]

Hint: Use %s for strings and %0.2f for 2-decimal floats [OK]

Common Mistakes:

• Swapping variable order
• Using %d for floats
• Using incorrect precision specifier