Function definition syntax in MATLAB - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of a simple function call

What is the output of this MATLAB code when calling result = addTwoNumbers(3, 5); disp(result);?

MATLAB

function sum = addTwoNumbers(a, b)
    sum = a + b;
end

A 8

B 35

C Error: Undefined function or variable 'addTwoNumbers'.

D 0

💡 Hint

Remember that the function adds the two input numbers.

The function addTwoNumbers takes two inputs and returns their sum. Calling it with 3 and 5 returns 8.

❓ Predict Output

intermediate

Output of a function with multiple outputs

What is the output of this MATLAB code snippet?
[minVal, maxVal] = findMinMax([4, 7, 1, 9]); disp([minVal, maxVal]);

MATLAB

function [minVal, maxVal] = findMinMax(arr)
    minVal = min(arr);
    maxVal = max(arr);
end

A Error: Too many output arguments.

B [4 7]

C [9 1]

D [1 9]

💡 Hint

The function returns the smallest and largest numbers in the array.

The function returns the minimum and maximum values of the input array. For [4,7,1,9], min is 1 and max is 9.

❓ Predict Output

advanced

Output of a nested function call

What is the output of this MATLAB code?
result = outerFunction(4); disp(result);

MATLAB

function out = outerFunction(x)
    function y = innerFunction(z)
        y = z^2;
    end
    out = innerFunction(x) + 1;
end

A 17

B 16

C Error: Nested functions are not allowed.

D 5

💡 Hint

The inner function squares the input, then 1 is added.

The inner function squares 4 to get 16, then outerFunction adds 1, resulting in 17.

❓ Predict Output

advanced

Output of a function with default argument behavior

What is the output of this MATLAB code?
disp(greet()); disp(greet('Alice'));

MATLAB

function message = greet(name)
    if nargin == 0
        name = 'Guest';
    end
    message = ['Hello, ', name, '!'];
end

A Hello, !<br>Hello, Alice!

B Hello, Guest!<br>Hello, Alice!

C Error: Not enough input arguments.

D Hello, Guest!<br>Hello, Guest!

💡 Hint

Check how the function handles missing input arguments.

If no input is given, the function sets name to 'Guest'. Otherwise, it uses the provided name.

❓ Predict Output

expert

Output of a recursive function

What is the output of this MATLAB code?
disp(factorialRecursive(4));

MATLAB

function f = factorialRecursive(n)
    if n == 0
        f = 1;
    else
        f = n * factorialRecursive(n - 1);
    end
end

A 1

B 10

C 24

D Error: Maximum recursion limit exceeded.

💡 Hint

Recall how factorial is calculated recursively.

Factorial of 4 is 4*3*2*1 = 24. The function calls itself until n=0, then multiplies back up.

Practice

1. Which of the following correctly describes the purpose of a function in MATLAB?

easy

A. To run MATLAB without installing it

B. To store data permanently on the computer

C. To create reusable blocks of code that perform specific tasks

D. To display graphics on the screen

Solution

1. Step 1: Understand what functions do

   Functions are designed to perform specific tasks repeatedly without rewriting code.

2. Step 2: Match purpose with options

   Only To create reusable blocks of code that perform specific tasks describes reusable code blocks, which is the main purpose of functions.

3. Final Answer:

   To create reusable blocks of code that perform specific tasks -> Option C

4. Quick Check:

   Function purpose = reusable code [OK]

Hint: Functions are for reusable code blocks [OK]

Common Mistakes:

• Confusing functions with data storage
• Thinking functions display graphics by default
• Assuming functions run MATLAB itself

2. Which of the following is the correct syntax to define a function named addNumbers that takes two inputs a and b and returns their sum c?

easy

A. function addNumbers = c(a, b)

B. function c = addNumbers(a, b)

C. def addNumbers(a, b):

D. func c(a, b) = addNumbers

Solution

1. Step 1: Recall MATLAB function syntax

   MATLAB functions start with the keyword 'function', then output(s), '=', function name, and input(s) in parentheses.

2. Step 2: Check each option

   function c = addNumbers(a, b) matches this syntax exactly. Options A, B, and D use incorrect keywords or order.

3. Final Answer:

   function c = addNumbers(a, b) -> Option B

4. Quick Check:

   function keyword + output = name(inputs) [OK]

Hint: Start with 'function', then output = name(inputs) [OK]

Common Mistakes:

• Using Python syntax like 'def'
• Placing function name before output incorrectly
• Using wrong keywords like 'func'

3. What will be the output of the following MATLAB function call?

function y = squareNum(x)
    y = x^2;
end

result = squareNum(4); disp(result);

medium

A. Error: Undefined function

B. 8

C. 4

D. 16

Solution

1. Step 1: Understand the function behavior

   The function squares the input number x by calculating x^2.

2. Step 2: Calculate the output for input 4

   4 squared is 4 * 4 = 16.

3. Final Answer:

   16 -> Option D

4. Quick Check:

   4 squared = 16 [OK]

Hint: Square input number to get output [OK]

Common Mistakes:

• Confusing ^ with multiplication
• Expecting addition instead of power
• Assuming function is undefined

4. Identify the error in the following MATLAB function definition:

function result = multiply(a, b)
result = a * b
end

medium

A. Missing semicolon after the multiplication statement

B. Function name does not match the file name

C. Incorrect use of the multiplication operator

D. Missing 'function' keyword

Solution

1. Step 1: Check syntax inside the function

   MATLAB statements should end with a semicolon to suppress output; here, it's missing after 'result = a * b'.

2. Step 2: Verify other parts

   The function keyword is present, the operator is correct, and file name matching is not shown but assumed correct.

3. Final Answer:

   Missing semicolon after the multiplication statement -> Option A

4. Quick Check:

   Statements need semicolon [OK]

Hint: End statements with semicolon to avoid errors [OK]

Common Mistakes:

• Forgetting semicolons after statements
• Assuming multiplication operator is wrong
• Ignoring file name and function name match

5. You want to create a MATLAB function named convertToFahrenheit that takes a Celsius temperature input and returns the Fahrenheit equivalent. Which of the following is the correct complete function definition?

hard

A. function F = convertToFahrenheit(C)
F = (C * 9/5) + 32;
end

B. function convertToFahrenheit = F(C)
F = (C + 32) * 9/5;
end

C. function F = convertToFahrenheit(C)
F = (C - 32) * 5/9;
end

D. function F = convertToFahrenheit(C)
F = C * 5/9 + 32;
end

Solution

1. Step 1: Recall the formula for Celsius to Fahrenheit

   The correct formula is Fahrenheit = (Celsius * 9/5) + 32.

2. Step 2: Check each function definition

   function F = convertToFahrenheit(C) F = (C * 9/5) + 32; end uses the correct formula and syntax. Options A, C, and D have wrong formulas or incorrect output variable assignment.

3. Final Answer:

   function F = convertToFahrenheit(C) F = (C * 9/5) + 32; end -> Option A

4. Quick Check:

   Celsius to Fahrenheit formula = (C * 9/5) + 32 [OK]

Hint: Use correct formula: F = (C * 9/5) + 32 [OK]

Common Mistakes:

• Mixing Celsius to Fahrenheit with Fahrenheit to Celsius formula
• Swapping output and function name
• Missing semicolons or wrong operators