Multiple outputs in MATLAB

Introduction

Sometimes you want a function to give back more than one answer at the same time. Multiple outputs let you do that easily.

When you want a function to return both the result and some extra information about it.

When you need to get several related values from one calculation.

When you want to avoid running the same code multiple times to get different results.

When you want to keep your code clean by grouping outputs together.

When you want to return both a value and a status or error code from a function.

Syntax

MATLAB

function [out1, out2, ..., outN] = functionName(inputs)
    % Your code here
end

Use square brackets [ ] to list multiple outputs separated by commas.

Call the function with the same number of output variables to get each result.

Examples

This function returns two outputs: the sum and the difference of two numbers.

MATLAB

function [sum, diff] = addAndSubtract(a, b)
    sum = a + b;
    diff = a - b;
end

Calling the function with two output variables captures both results.

MATLAB

[s, d] = addAndSubtract(5, 3)
% s will be 8, d will be 2

You can choose to get only the first output if you want.

MATLAB

[onlySum] = addAndSubtract(5, 3)
% onlySum will be 8, difference is ignored

Sample Program

This program defines a function that returns both the area and perimeter of a rectangle. Then it calls the function and prints both results.

MATLAB

function [area, perimeter] = rectangleProperties(length, width)
    area = length * width;
    perimeter = 2 * (length + width);
end

% Call the function
[lArea, lPerimeter] = rectangleProperties(4, 7);

% Display the results
fprintf('Area: %d\n', lArea);
fprintf('Perimeter: %d\n', lPerimeter);

Important Notes

If you call a function with fewer output variables than it returns, MATLAB ignores the extra outputs.

If you call a function with more output variables than it returns, MATLAB gives an error.

Use multiple outputs to keep your code efficient and organized.

Summary

Multiple outputs let a function return several values at once.

Use square brackets to list outputs in the function definition.

Call the function with matching output variables to get each result.

Practice

1. In MATLAB, how do you define a function that returns multiple outputs?

easy

A. Separate output variables with commas without brackets.

B. Use square brackets around output variables in the function definition.

C. Use parentheses around output variables in the function definition.

D. Define each output in a separate function.

Solution

1. Step 1: Understand MATLAB function output syntax

   MATLAB requires multiple outputs to be enclosed in square brackets in the function definition. Only Use square brackets around output variables in the function definition. correctly uses square brackets; others are invalid syntax or incorrect approach.

2. Final Answer:

   Use square brackets around output variables in the function definition. -> Option B

3. Quick Check:

   Multiple outputs = square brackets [OK]

Hint: Remember: multiple outputs always use square brackets [OK]

Common Mistakes:

• Using parentheses instead of square brackets
• Listing outputs without any brackets
• Trying to define outputs in separate functions

2. Which of the following is the correct syntax to call a MATLAB function myFunc that returns two outputs?

easy

A. [a, b] = myFunc(x);

B. a, b = myFunc(x);

C. (a, b) = myFunc(x);

D. a = myFunc(x); b = myFunc(x);

Solution

1. Step 1: Recall MATLAB function call syntax for multiple outputs

   Multiple outputs must be captured using square brackets on the left side of the assignment. [a, b] = myFunc(x); uses correct square brackets; B and C use invalid syntax; A calls function twice, not multiple outputs.

2. Final Answer:

   [a, b] = myFunc(x); -> Option A

3. Quick Check:

   Multiple outputs call = square brackets [OK]

Hint: Use square brackets to capture multiple outputs when calling [OK]

Common Mistakes:

• Using parentheses or commas without brackets
• Calling function multiple times instead of one call
• Missing brackets around output variables

3. What is the output of this MATLAB code?

function [sumVal, diffVal] = calc(a, b)
    sumVal = a + b;
    diffVal = a - b;
end

[x, y] = calc(5, 3);

What are the values of x and y?

medium

A. x = 5, y = 3

B. x = 2, y = 8

C. x = 8, y = 2

D. x = 15, y = 2

Solution

1. Step 1: Trace function execution and match outputs

   The function returns sumVal = a + b = 5 + 3 = 8 and diffVal = a - b = 5 - 3 = 2. x receives sumVal (8), y receives diffVal (2).

2. Final Answer:

   x = 8, y = 2 -> Option C

3. Quick Check:

   sum = 8, diff = 2 [OK]

Hint: First output = sum, second output = difference [OK]

Common Mistakes:

• Swapping order of outputs
• Confusing inputs with outputs
• Adding instead of subtracting for difference

4. Identify the error in this MATLAB function that tries to return two outputs:

function [a, b] = wrongFunc(x)
    a = x * 2;
    b = x + 3
end

medium

A. Square brackets not allowed in output

B. Function must return only one output

C. Function name does not match file name

D. Missing semicolon after assigning b

Solution

1. Step 1: Check syntax line by line

   Line assigning b lacks a semicolon, causing output to print unexpectedly. Multiple outputs with square brackets are allowed; function name matching file is good practice but not error here.

2. Final Answer:

   Missing semicolon after assigning b -> Option D

3. Quick Check:

   Missing semicolon = syntax error [OK]

Hint: Always end statements with semicolon to avoid output [OK]

Common Mistakes:

• Ignoring missing semicolons
• Thinking multiple outputs are not allowed
• Confusing function name and file name mismatch as error

5. You want to write a MATLAB function stats that takes a vector and returns three outputs: the mean, median, and standard deviation. Which function header and call are correct?

hard

A. Function: function [m, med, s] = stats(v)Call: [meanVal, medianVal, stdVal] = stats(data);

B. Function: function (m, med, s) = stats(v)Call: (meanVal, medianVal, stdVal) = stats(data);

C. Function: function m, med, s = stats(v)Call: meanVal, medianVal, stdVal = stats(data);

D. Function: function stats(v) returns m, med, sCall: stats(data)

Solution

1. Step 1: Verify function header and call syntax

   Multiple outputs must use square brackets in the function header: function [m, med, s] = stats(v) and in the call: [meanVal, medianVal, stdVal] = stats(data);. Others use invalid parentheses, commas without brackets, or incorrect formats.

2. Final Answer:

   Function and call with square brackets for multiple outputs -> Option A

3. Quick Check:

   Multiple outputs = square brackets in header and call [OK]

Hint: Use square brackets for multiple outputs in both function and call [OK]

Common Mistakes:

• Using parentheses instead of square brackets
• Not capturing all outputs in call
• Incorrect function header syntax