Type checking (class, isa) in MATLAB - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this MATLAB code using class()?

Consider the following MATLAB code snippet:

var = 3.14;
disp(class(var));

What will be printed to the console?

MATLAB

var = 3.14;
disp(class(var));

A double

B single

C int32

D char

💡 Hint

Check the default numeric type for decimal numbers in MATLAB.

In MATLAB, numeric literals with decimals are of type double by default. So, class(3.14) returns double.

❓ Predict Output

intermediate

What does isa() return for a cell array?

Given this MATLAB code:

c = {1, 2, 3};
result = isa(c, 'cell');
disp(result);

What is the output?

MATLAB

c = {1, 2, 3};
result = isa(c, 'cell');
disp(result);

A 1

B 0

C 'true'

D 'false'

💡 Hint

isa returns logical true (1) or false (0).

The variable c is a cell array, so isa(c, 'cell') returns logical 1 (true).

❓ Predict Output

advanced

What is the output of isa() for a subclass object?

Suppose you have a class Animal and a subclass Dog. Consider this code:

classdef Animal
end

classdef Dog < Animal
end

obj = Dog();
disp(isa(obj, 'Animal'));

What will be displayed?

MATLAB

classdef Animal
end

classdef Dog < Animal
end

obj = Dog();
disp(isa(obj, 'Animal'));

A Error: Undefined function or variable 'Dog'

B 0

C Error: Invalid class definition

D 1

💡 Hint

isa returns true if the object is an instance of the class or its subclass.

Since Dog inherits from Animal, isa(obj, 'Animal') returns true (1).

❓ Predict Output

advanced

What error does this code raise when using class() on an undefined variable?

Analyze this MATLAB code:

disp(class(undefinedVar));

What error message will MATLAB produce?

MATLAB

disp(class(undefinedVar));

A Error: Invalid class name.

B Error: Syntax error near 'class'.

C Error: Undefined function or variable 'undefinedVar'.

D No error, prints 'double'.

💡 Hint

Check what happens when you use a variable that was never created.

MATLAB throws an error because undefinedVar does not exist in the workspace.

🧠 Conceptual

expert

Which option correctly checks if a variable is numeric or a subclass of numeric?

You want to check if a variable x is numeric or any subclass of numeric types in MATLAB. Which code snippet correctly does this?

A isa(x, 'double') || isa(x, 'single')

B isnumeric(x)

C class(x) == 'numeric'

D isa(x, 'numeric')

💡 Hint

Consider built-in functions designed for type checking of numeric data.

isnumeric(x) returns true if x is any numeric type (double, single, int, etc.). isa(x, 'numeric') is invalid because 'numeric' is not a class name. Checking class equality with == is incorrect for strings.