Anonymous functions in MATLAB - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is an anonymous function in MATLAB?

An anonymous function is a simple, unnamed function defined in a single line using the @ symbol. It allows quick creation of functions without saving them as separate files.

beginner

How do you define an anonymous function that squares a number x in MATLAB?

You write: square = @(x) x.^2; This creates a function named 'square' that returns x squared.

beginner

Can anonymous functions in MATLAB accept multiple inputs? Give an example.

Yes. For example: add = @(a,b) a + b; This function adds two inputs a and b.

intermediate

What is a common use case for anonymous functions in MATLAB?

They are often used for quick calculations, passing functions as arguments to other functions like arrayfun or integral, without creating separate function files.

intermediate

How do anonymous functions capture variables from the workspace?

Anonymous functions can use variables defined outside their definition. These variables are 'captured' by value at the time the function is created.

How do you start defining an anonymous function in MATLAB?

A With the # symbol

B With the function keyword

C With the $ symbol

D With the @ symbol

Anonymous functions in MATLAB always start with the @ symbol followed by input arguments.

What does this anonymous function do? f = @(x) x + 5;

A Subtracts 5 from input x

B Multiplies input x by 5

C Adds 5 to input x

D Divides input x by 5

The function adds 5 to the input x.

Can anonymous functions be saved as separate files in MATLAB?

A No, they are defined inline

B Yes, always

C Only if named

D Only in scripts

Anonymous functions are meant to be quick, inline functions and are not saved as separate files.

Which of these is a valid anonymous function with two inputs?

A lambda x,y: x*y

B @(x,y) x*y

C def f(x,y): x*y

D function(x,y) x*y

MATLAB anonymous functions use @(inputs) expression syntax.

What happens if an anonymous function uses a variable from outside its definition?

A It captures the variable's value at creation time

B It ignores the variable

C It causes an error

D It updates the variable dynamically

Anonymous functions capture external variables by value when created.

Explain how to create and use an anonymous function in MATLAB with an example.

Think about how you write a quick function without a file.

Describe a practical situation where anonymous functions are useful in MATLAB programming.

Consider when you want to do small tasks inside other functions.

Practice

1. What is an anonymous function in MATLAB?

easy

A. A quick, unnamed function created using the '@' symbol.

B. A function saved in a separate file with a name.

C. A function that can only be used inside loops.

D. A function that requires no input arguments.

Solution

1. Step 1: Understand the definition of anonymous functions

   Anonymous functions in MATLAB are small, unnamed functions created using the '@' symbol.

2. Step 2: Compare options with the definition

   A quick, unnamed function created using the '@' symbol. correctly describes anonymous functions as quick, unnamed functions created with '@'. Other options describe named functions or incorrect properties.

3. Final Answer:

   A quick, unnamed function created using the '@' symbol. -> Option A

4. Quick Check:

   Anonymous function = unnamed function with '@' [OK]

Hint: Look for '@' symbol to identify anonymous functions [OK]

Common Mistakes:

• Confusing anonymous functions with regular named functions
• Thinking anonymous functions must have no inputs
• Assuming anonymous functions are saved in separate files

2. Which of the following is the correct syntax to create an anonymous function that squares its input x?

easy

A. f = @(x) x^2;

B. f = function(x) x^2;

C. f = @x x^2;

D. f = (x) => x^2;

Solution

1. Step 1: Recall MATLAB anonymous function syntax

   The correct syntax uses '@(args) expression;' so for squaring x, it is '@(x) x^2;'.

2. Step 2: Check each option

   f = @(x) x^2; matches the correct syntax. f = function(x) x^2; uses incorrect keyword 'function'. f = @x x^2; misses parentheses. f = (x) => x^2; uses arrow syntax from other languages.

3. Final Answer:

   f = @(x) x^2; -> Option A

4. Quick Check:

   Anonymous function syntax = @(args) expression [OK]

Hint: Remember '@(x) expression;' for anonymous functions [OK]

Common Mistakes:

• Omitting parentheses around input arguments
• Using 'function' keyword inside anonymous function
• Using arrow syntax from other languages

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

f = @(x) x + 5;
result = f(10);
disp(result);

medium

A. 5

B. 10

C. 15

D. Error

Solution

1. Step 1: Understand the anonymous function definition

   The function f adds 5 to its input x.

2. Step 2: Calculate the function output for input 10

   f(10) = 10 + 5 = 15.

3. Final Answer:

   15 -> Option C

4. Quick Check:

   10 + 5 = 15 [OK]

Hint: Apply input to expression inside @(x) function [OK]

Common Mistakes:

• Confusing input and output values
• Expecting function to multiply instead of add
• Thinking anonymous functions cause errors without file

4. Identify the error in this MATLAB anonymous function:

g = @x x^2 + 3;

medium

A. Anonymous functions cannot use addition.

B. Missing parentheses around input argument x.

C. The '@' symbol is not allowed here.

D. The function must be saved in a separate file.

Solution

1. Step 1: Check anonymous function syntax

   Anonymous functions require parentheses around input arguments, like '@(x)'.

2. Step 2: Identify the syntax error

   The code uses '@x' without parentheses, which is invalid syntax.

3. Final Answer:

   Missing parentheses around input argument x. -> Option B

4. Quick Check:

   Anonymous function input must be in parentheses [OK]

Hint: Always use @(input) with parentheses [OK]

Common Mistakes:

• Omitting parentheses around inputs
• Thinking '@' can be used without parentheses
• Believing anonymous functions need separate files

5. You want to create an anonymous function h that takes two inputs x and y and returns x squared plus y cubed. Which is the correct way to write this?

hard

A. h = @(x y) x^2 + y^3;

B. h = @(x,y) x^2 * y^3;

C. h = @(x,y) (x^2), (y^3);

D. h = @(x,y) x^2 + y^3;

Solution

1. Step 1: Understand multiple inputs in anonymous functions

   Multiple inputs are separated by commas inside parentheses: @(x,y).

2. Step 2: Check the expression for correct operations

   The function should return x squared plus y cubed, so use '+' operator, not '*'.

3. Final Answer:

   h = @(x,y) x^2 + y^3; -> Option D

4. Quick Check:

   Multiple inputs use commas; '+' adds results [OK]

Hint: Separate inputs with commas and use correct operators [OK]

Common Mistakes:

• Omitting commas between inputs
• Using wrong operators like multiplication instead of addition
• Trying to separate expressions with commas outside parentheses