Input and output arguments in MATLAB - Mini Project: Build & Apply

Input and Output Arguments in MATLAB Functions

📖 Scenario: You are creating a simple calculator function in MATLAB that takes two numbers and returns their sum.

🎯 Goal: Build a MATLAB function that accepts two input arguments and returns their sum as an output argument.

📋 What You'll Learn

Create a function named addNumbers that takes exactly two input arguments named a and b.

The function must return one output argument named result which is the sum of a and b.

Call the function with the numbers 5 and 7 and store the output in a variable named sumResult.

Display the value of sumResult using disp.

💡 Why This Matters

🌍 Real World

Functions with input and output arguments are used in MATLAB to organize code and reuse calculations, such as in engineering simulations or data analysis.

💼 Career

Understanding how to write and use functions with inputs and outputs is essential for MATLAB programming jobs in science, engineering, and research.

1

Create the function header

Write the first line of the function addNumbers that takes two input arguments a and b and returns one output argument result.

MATLAB

% Define the function header for addNumbers with inputs a and b and output result
% Your code here

Hint

Use the syntax: function output = functionName(input1, input2)

2

Add the calculation inside the function

Inside the function addNumbers, write a line that adds a and b and stores the result in result.

MATLAB

function result = addNumbers(a, b)
    % Add a and b and store in result
    % Your code here

Hint

Use the plus operator + to add the two inputs.

3

Call the function with inputs

Call the function addNumbers with inputs 5 and 7 and store the output in a variable named sumResult.

MATLAB

function result = addNumbers(a, b)
    result = a + b;
end

% Call addNumbers with 5 and 7 and store in sumResult
% Your code here

Hint

Use the syntax: outputVar = functionName(input1, input2);

4

Display the result

Use disp to display the value of sumResult.

MATLAB

function result = addNumbers(a, b)
    result = a + b;
end

sumResult = addNumbers(5, 7);

% Display sumResult
% Your code here

Hint

Use disp(variableName) to print the value.

Practice

1. What is the main purpose of input arguments in a MATLAB function?

easy

A. To send data into the function for processing

B. To display results on the screen

C. To store variables permanently

D. To create new functions inside the main function

Solution

1. Step 1: Understand input arguments

   Input arguments are values or data you give to a function so it can use them inside.

2. Step 2: Identify the purpose

   The main purpose is to send data into the function for it to work on.

3. Final Answer:

   To send data into the function for processing -> Option A

4. Quick Check:

   Input arguments = send data in [OK]

Hint: Input arguments bring data into functions [OK]

Common Mistakes:

• Confusing input arguments with output arguments
• Thinking input arguments display results
• Assuming input arguments create new functions

2. Which of the following is the correct syntax to define a MATLAB function with one input and one output argument?

easy

A. function output = myFunc(input)

B. function myFunc(input) = output

C. function (output) = myFunc input

D. function myFunc output(input)

Solution

1. Step 1: Recall MATLAB function syntax

   The correct syntax starts with 'function', then output, '=', function name, and input in parentheses.

2. Step 2: Match the syntax

   function output = myFunc(input) matches this pattern exactly: function output = myFunc(input)

3. Final Answer:

   function output = myFunc(input) -> Option A

4. Quick Check:

   Syntax = function output = name(input) [OK]

Hint: Output = functionName(input) is the right order [OK]

Common Mistakes:

• Placing output after function name without '='
• Missing parentheses around input
• Using '=' incorrectly in function header

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

function y = squarePlusOne(x)
    y = x^2 + 1;
end

result = squarePlusOne(3);

medium

A. 9

B. 10

C. 7

D. 16

Solution

1. Step 1: Calculate the square of input

   Input x is 3, so x^2 = 3^2 = 9.

2. Step 2: Add 1 to the squared value

   9 + 1 = 10.

3. Final Answer:

   10 -> Option B

4. Quick Check:

   3 squared plus 1 = 10 [OK]

Hint: Square input, then add one [OK]

Common Mistakes:

• Forgetting to add 1 after squaring
• Using multiplication instead of power
• Confusing output with input

4. Identify the error in this MATLAB function definition:

function output = addNumbers(a, b)
    output = a + b
end

medium

A. Input arguments must be in square brackets

B. Function name should be capitalized

C. Output variable cannot be named 'output'

D. Missing semicolon after output assignment

Solution

1. Step 1: Check MATLAB syntax rules

   Each statement should end with a semicolon to suppress output in functions.

2. Step 2: Identify missing semicolon

   The line 'output = a + b' lacks a semicolon at the end.

3. Final Answer:

   Missing semicolon after output assignment -> Option D

4. Quick Check:

   Statements need semicolons [OK]

Hint: End statements with semicolon inside functions [OK]

Common Mistakes:

• Ignoring semicolon causes unwanted output
• Thinking function names must be capitalized
• Using wrong brackets for inputs

5. You want to write a MATLAB function that takes two numbers as input and returns both their sum and product as outputs. Which function header is correct?

hard

A. function sum, product = calculate(a, b)

B. function calculate(a, b) = [sum, product]

C. function [sum, product] = calculate(a, b)

D. function calculate = [sum, product](a, b)

Solution

1. Step 1: Recall syntax for multiple outputs

   Multiple outputs are enclosed in square brackets before the '=' sign.

2. Step 2: Match correct syntax

   function [sum, product] = calculate(a, b) uses square brackets for outputs and correct order: function [sum, product] = calculate(a, b)

3. Final Answer:

   function [sum, product] = calculate(a, b) -> Option C

4. Quick Check:

   Multiple outputs use square brackets [OK]

Hint: Use square brackets for multiple outputs [OK]

Common Mistakes:

• Omitting square brackets for multiple outputs
• Placing outputs after function name without brackets
• Using '=' incorrectly in function header