Function definition syntax in MATLAB - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the basic syntax to define a function in MATLAB?

Use the function keyword followed by the output variable(s), the function name, and input variable(s). Example:

function output = functionName(input)

beginner

How do you define a function with multiple outputs in MATLAB?

List the output variables inside square brackets separated by commas. Example:

function [out1, out2] = myFunction(in1, in2)

intermediate

Where must the function definition be placed in a MATLAB file?

The function definition must be the first executable line in the file if it is a function file. If the file contains multiple functions, the first function is the main function, and others are local functions below it.

beginner

Can MATLAB functions have no input or no output arguments? How?

Yes. For no inputs, just omit input variables:<br><pre>function output = myFunction()</pre><br>For no outputs, omit output variables:<br><pre>function myFunction(input)</pre>

intermediate

What happens if you do not specify output variables in a MATLAB function?

The function will not return any output to the caller. It can still perform actions like displaying results or modifying files, but no data is returned.

Which keyword starts a function definition in MATLAB?

A function

B def

C func

D begin

MATLAB uses the keyword function to define functions.

How do you define a function with two outputs named a and b?

A function [a, b] = myFunc()

B function a, b = myFunc()

C function (a, b) = myFunc()

D function a b = myFunc()

Multiple outputs are enclosed in square brackets separated by commas.

Where should the main function be placed in a MATLAB file?

A Inside a script section

B At the top of the file

C At the bottom of the file

D Anywhere in the file

The main function must be the first executable line in the file.

What is the correct way to define a function with no inputs but one output?

A function out = myFunc

B function myFunc()

C function out = myFunc()

D function myFunc

Use empty parentheses to indicate no inputs.

If a MATLAB function does not specify output variables, what happens?

A It causes an error

B It returns the first input

C It returns a default variable

D No output is returned

Without output variables, the function returns nothing to the caller.

Explain the syntax to define a MATLAB function with multiple outputs and inputs.

Think about how you list outputs and inputs in the function line.

Describe where and how you place function definitions inside a MATLAB file.

Consider the order of functions in the file.

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