String formatting (sprintf) in MATLAB - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of sprintf with integer and float formatting

What is the output of the following MATLAB code?

str = sprintf('Value: %d, Pi approx: %.2f', 7, 3.14159); disp(str);

MATLAB

str = sprintf('Value: %d, Pi approx: %.2f', 7, 3.14159); disp(str);

A Value: 7, Pi approx: 3.14159

B Value: 7, Pi approx: 3.14

C Value: 7, Pi approx: 3.1

D Value: 7, Pi approx: 3

💡 Hint

Look at the %.2f format specifier; it rounds to two decimal places.

The %d formats the integer 7 as is. The %.2f rounds the float 3.14159 to two decimal places, resulting in 3.14.

❓ Predict Output

intermediate

Using sprintf to format a date string

What will be the output of this MATLAB code?

day = 5; month = 9; year = 2024; str = sprintf('Date: %02d/%02d/%04d', day, month, year); disp(str);

MATLAB

day = 5; month = 9; year = 2024; str = sprintf('Date: %02d/%02d/%04d', day, month, year); disp(str);

A Date: 5/9/2024

B Date: 05/9/2024

C Date: 05/09/2024

D Date: 5/09/2024

💡 Hint

The %02d means pad with zeros to 2 digits, %04d pads to 4 digits.

The day and month are padded with zeros to two digits, so 5 becomes 05 and 9 becomes 09. The year is padded to 4 digits, but it is already 4 digits.

❓ Predict Output

advanced

Output of sprintf with mixed format specifiers

What is the output of this MATLAB code?

str = sprintf('Hex: %X, Oct: %o, Char: %c', 255, 8, 65); disp(str);

MATLAB

str = sprintf('Hex: %X, Oct: %o, Char: %c', 255, 8, 65); disp(str);

A Hex: FF, Oct: 10, Char: A

B Hex: ff, Oct: 8, Char: 65

C Hex: FF, Oct: 8, Char: A

D Hex: 255, Oct: 10, Char: 65

💡 Hint

Remember %X prints uppercase hex, %o prints octal, %c prints character from ASCII code.

255 in hex is FF, 8 in octal is 10, and ASCII code 65 is character 'A'.

❓ Predict Output

advanced

sprintf with width and left alignment

What will this MATLAB code display?

str = sprintf('|%-10s|%5d|', 'Hi', 42); disp(str);

MATLAB

str = sprintf('|%-10s|%5d|', 'Hi', 42); disp(str);

A |Hi | 42|

B | Hi| 42|

C |Hi |42 |

D |Hi| 42|

💡 Hint

%-10s means left-align string in 10 spaces; %5d means right-align integer in 5 spaces.

The string 'Hi' is left aligned in a 10-character field, padded with spaces on the right. The number 42 is right aligned in a 5-character field, padded with spaces on the left.

🧠 Conceptual

expert

Understanding sprintf behavior with multiple format specifiers

Consider this MATLAB code:

str = sprintf('%d %d %d', 1, 2); disp(str);

What happens when you run this code?

A It prints '1 2' ignoring the last format specifier.

B It prints '1 2 0' because missing arguments default to zero.

C It prints '1 2 2' repeating the last argument.

D It raises an error because there are fewer input arguments than format specifiers.

💡 Hint

Check how MATLAB handles missing arguments for sprintf.

MATLAB requires the number of arguments to match the number of format specifiers. Missing arguments cause an error.