Structures and field access in MATLAB - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Accessing nested structure fields

What is the output of the following MATLAB code?

MATLAB

person.name = 'Alice';
person.age = 30;
person.address.city = 'New York';
person.address.zip = 10001;
disp(person.address.city);

A Error: Field 'city' does not exist

B person.address.city

C 10001

D New York

💡 Hint

Use dot notation to access nested fields.

The code accesses the nested field 'city' inside 'address' of the 'person' structure, which holds the string 'New York'.

❓ Predict Output

intermediate

Modifying a structure field

What is the value of 'car.color' after running this code?

MATLAB

car.make = 'Toyota';
car.color = 'Red';
car.color = 'Blue';

A Error: Cannot modify field

B 'Red'

C 'Blue'

D '' (empty string)

💡 Hint

The last assignment changes the field value.

The field 'color' is first set to 'Red' and then changed to 'Blue'. The final value is 'Blue'.

❓ Predict Output

advanced

Accessing a non-existent field

What happens when this MATLAB code runs?

MATLAB

data.temperature = 25;
disp(data.humidity);

A Error: Reference to non-existent field 'humidity'.

B Displays 0

C Displays empty array []

D Displays NaN

💡 Hint

Accessing a field that was never created causes an error.

MATLAB throws an error when trying to access a field that does not exist in the structure.

🧠 Conceptual

advanced

Structure array field access

Given the structure array 'students' below, what is the output of
disp(students(2).name)?

MATLAB

students(1).name = 'John';
students(1).grade = 85;
students(2).name = 'Emma';
students(2).grade = 92;

A John

B Emma

C 85

D Error: Index exceeds array bounds

💡 Hint

Use parentheses to access elements in a structure array.

students(2) accesses the second element of the structure array, and '.name' accesses the 'name' field, which is 'Emma'.

❓ Predict Output

expert

Dynamic field names in structures

What is the output of this MATLAB code?

MATLAB

fieldName = 'score';
result.(fieldName) = 100;
disp(result.score);

A 100

B fieldName

C Error: Invalid field name

D []

💡 Hint

You can use parentheses and a variable to access or create fields dynamically.

The code creates a field named 'score' dynamically using the variable 'fieldName' and assigns it 100. Displaying result.score shows 100.