Multiple outputs in MATLAB - Step-by-Step Execution

Concept Flow - Multiple outputs

Call function with multiple outputs

↓

Function runs code

↓

Assign values to output variables

↓

Return outputs to caller

↓

Caller receives multiple outputs

↓

Use outputs separately

This flow shows how a MATLAB function can return multiple outputs, which the caller receives and uses separately.

Execution Sample

MATLAB

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

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

This code defines a function that returns two outputs: sum and difference of two inputs, then calls it to get both results.

Execution Table

Step	Action	Variables	Output Variables Assigned	Result
1	Call addAndSubtract(5, 3)	a=5, b=3	None yet	Function starts
2	Calculate sumVal = a + b	a=5, b=3	sumVal=8	sumVal assigned 8
3	Calculate diffVal = a - b	a=5, b=3	diffVal=2	diffVal assigned 2
4	Return outputs to caller	sumVal=8, diffVal=2	x=8, y=2	Outputs assigned to x and y
5	Use outputs x and y	x=8, y=2	None	x=8, y=2 ready for use

💡 Function ends after returning both outputs to caller

Variable Tracker

Variable	Start	After Step 2	After Step 3	After Step 4	Final
a	undefined	5	5	5	5
b	undefined	3	3	3	3
sumVal	undefined	8	8	8	8
diffVal	undefined	undefined	2	2	2
x	undefined	undefined	undefined	8	8
y	undefined	undefined	undefined	2	2

Key Moments - 3 Insights

Why do we use square brackets [ ] when calling the function?

Square brackets tell MATLAB to expect multiple outputs. Without them, only the first output is returned (see execution_table step 4).

What happens if we ask for fewer outputs than the function provides?

MATLAB returns only the requested outputs. For example, if only one output is requested, only sumVal is returned (not shown here but implied by step 4).

Can we ignore some outputs when calling the function?

Yes, you can use ~ to ignore outputs you don't need, but the function still computes them internally (not shown in table but common practice).

Visual Quiz - 3 Questions

Look at the execution_table at step 3, what is the value of diffVal?

A 2

B 3

C 8

D 5

💡 Hint

Check the 'Output Variables Assigned' column at step 3 in execution_table.

At which step are the outputs assigned to variables x and y in the caller?

A Step 2

B Step 4

C Step 3

D Step 5

💡 Hint

Look for when 'Outputs assigned to x and y' happens in execution_table.

If we call the function without square brackets, what will happen?

A An error occurs

B Both outputs are assigned to x

C Only the first output is returned

D All outputs are ignored

💡 Hint

Recall key_moments about output assignment and square brackets usage.

Concept Snapshot

Multiple outputs in MATLAB:
- Use [out1, out2, ...] = functionName(inputs)
- Function defines outputs in square brackets
- Caller receives outputs in order
- Use ~ to ignore outputs
- Without brackets, only first output returned

Full Transcript

This visual trace shows how MATLAB functions can return multiple outputs. The function addAndSubtract takes two inputs and returns two outputs: their sum and difference. The execution table walks through each step: calling the function, calculating outputs, and assigning them back to variables x and y in the caller. The variable tracker shows how each variable changes after each step. Key moments clarify why square brackets are needed to receive multiple outputs and what happens if fewer outputs are requested. The quiz tests understanding of output values and assignment steps. The snapshot summarizes the syntax and behavior for quick reference.

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