Multiple outputs in MATLAB - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of a function with multiple outputs

What is the output of the following MATLAB code?

MATLAB

function [a, b] = example(x)
    a = x + 1;
    b = x * 2;
end

[a_out, b_out] = example(3);
disp([a_out, b_out]);

A [6 4]

B [3 6]

C [4 6]

D [4 3]

💡 Hint

Remember the function adds 1 to x for the first output and multiplies x by 2 for the second output.

The function returns two outputs: a = x + 1 = 4, and b = x * 2 = 6. So the displayed array is [4 6].

❓ Predict Output

intermediate

Using only one output from a function with multiple outputs

What will be the output of this MATLAB code?

MATLAB

function [a, b] = example(x)
    a = x^2;
    b = x^3;
end

result = example(2);
disp(result);

A [4 8]

B 4

C [2 4]

D Error: Too many output arguments.

💡 Hint

When calling a function with multiple outputs but only one variable, MATLAB returns the first output.

Only the first output 'a' is assigned to 'result', which is 2^2 = 4.

🔧 Debug

advanced

Identify the error in multiple output assignment

What error will this MATLAB code produce?

MATLAB

function [x, y] = calc()
    x = 5;
    y = 10;
end

[a, b, c] = calc();

A Error: Undefined function or variable 'c'.

B Error: Not enough output arguments.

C No error, a=5, b=10, c=0

D Error: Too many output arguments.

💡 Hint

The function returns only two outputs but you are trying to assign three.

The function returns two outputs but the caller expects three, causing a 'Too many output arguments' error.

❓ Predict Output

advanced

Output of nested function calls with multiple outputs

What is the output of this MATLAB code?

MATLAB

function [sumVal, prodVal] = compute(a, b)
    sumVal = a + b;
    prodVal = a * b;
end

[x, y] = compute(2, 3);
[z, w] = compute(x, y);
disp([z, w]);

A [11 30]

B [5 6]

C [5 15]

D [6 7]

💡 Hint

First compute(2,3) returns sum=5 and product=6. Then compute(5,6) returns sum=11 and product=30.

First call: [x, y] = compute(2, 3) returns x=5, y=6. Second call: [z, w] = compute(5, 6) returns z=11, w=30. disp([z, w]) displays [11 30].

❓ Predict Output

expert

Multiple outputs with conditional assignment

What is the output of this MATLAB code?

MATLAB

function [a, b] = conditionalOutputs(x)
    if x > 0
        a = x;
        b = x^2;
    else
        a = -x;
        b = -x^2;
    end
end

[p, q] = conditionalOutputs(-3);
disp([p, q]);

A [3 -9]

B [-3 -9]

C [3 9]

D [-3 9]

💡 Hint

Check the else branch for negative input values.

Since x = -3 (less than 0), a = -(-3) = 3, b = -((-3)^2) = -9, so output is [3 -9].

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