Anonymous functions in MATLAB

Introduction

Anonymous functions let you create quick, simple functions without giving them a name. They are useful for small tasks where writing a full function file is too much work.

When you need a small function for a short calculation inside your script.

When you want to pass a simple function as an input to another function.

When you want to avoid creating many separate function files for tiny tasks.

When you want to quickly test a function without saving it permanently.

Syntax

MATLAB

f = @(arg1, arg2, ...) expression;

The '@' symbol starts the anonymous function.

Arguments go inside parentheses after '@'.

The expression is what the function calculates and returns.

Examples

Creates a function 'square' that returns the square of input x.

MATLAB

square = @(x) x.^2;

Creates a function 'add' that adds two inputs a and b.

MATLAB

add = @(a,b) a + b;

Creates a function 'greet' that returns a greeting message with the input name.

MATLAB

greet = @(name) ['Hello, ' name '!'];

Sample Program

This program defines an anonymous function to square a number, then uses it to find the square of 5 and displays the result.

MATLAB

square = @(x) x.^2;
result = square(5);
disp(['Square of 5 is: ' num2str(result)]);

Important Notes

Anonymous functions can only contain one expression, no multiple statements.

Use dot operators (like .^) for element-wise operations on arrays.

They are handy for quick calculations but for complex logic, use regular functions.

Summary

Anonymous functions are quick, unnamed functions created with '@'.

They are great for small tasks and passing functions as arguments.

Syntax: f = @(args) expression; where expression is what the function returns.

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