Structure arrays in MATLAB - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a structure array with field 'name'.

MATLAB

person = struct('[1]', 'Alice');

Drag options to blanks, or click blank then click option'

Aname

Bage

Cheight

Dweight

Attempts:

3 left

💡 Hint

Common Mistakes

Using a field name that does not match the data, like 'age' or 'height'.

The field name 'name' is used to store the person's name in the structure.

2fill in blank

medium

Complete the code to add a second element to the structure array.

MATLAB

person(2) = struct('[1]', 'Bob');

Drag options to blanks, or click blank then click option'

Aage

Bheight

Cname

Dweight

Attempts:

3 left

💡 Hint

Common Mistakes

Using a different field name for the second element.

To add a second element with the same field, use 'name' as the field.

3fill in blank

hard

Fix the error in the code to correctly create a structure array with fields 'name' and 'age'.

MATLAB

person = struct('name', 'Alice', '[1]', 30);

Drag options to blanks, or click blank then click option'

Aweight

Bage

Cbirthdate

Dheight

Attempts:

3 left

💡 Hint

Common Mistakes

Using unrelated field names like 'height' or 'weight'.

The second field should be 'age' to store the person's age.

4fill in blank

hard

Fill both blanks to create a structure array with fields 'name' and 'age' for two people.

MATLAB

people(1) = struct('[1]', 'Alice', '[2]', 30);

Drag options to blanks, or click blank then click option'

Aname

Bheight

Cage

Dweight

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping the fields or using unrelated field names.

The first field is 'name' and the second is 'age' to store the correct data.

5fill in blank

hard

Fill all three blanks to create a structure array with fields 'name', 'age', and 'height' for two people.

MATLAB

people(2) = struct('[1]', 'Bob', '[2]', 25, '[3]', 180);

Drag options to blanks, or click blank then click option'

Aweight

Bage

Cheight

Dname

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong field names or wrong order of fields.

The fields must be 'name', 'age', and 'height' in that order to match the data.

Practice

1. What is a structure array in MATLAB used for?

easy

A. To perform matrix multiplication

B. To store only numeric arrays

C. To group related data with different types under named fields

D. To create loops for iteration

Solution

1. Step 1: Understand the purpose of structure arrays

   Structure arrays allow grouping of different types of data under named fields.

2. Step 2: Compare options with the definition

   Only To group related data with different types under named fields correctly describes this use; others describe unrelated concepts.

3. Final Answer:

   To group related data with different types under named fields -> Option C

4. Quick Check:

   Structure arrays = group data by fields [OK]

Hint: Remember: structures group different data types by names [OK]

Common Mistakes:

• Thinking structures only hold numeric data
• Confusing structures with loops or matrices

2. Which of the following is the correct way to create a structure array with fields 'Name' and 'Age' in MATLAB?

easy

A. person = struct('Name', 'Alice', 'Age', 30);

B. person = struct(Name = 'Alice', Age = 30);

C. person = struct['Name', 'Alice', 'Age', 30];

D. person = struct{'Name', 'Alice', 'Age', 30};

Solution

1. Step 1: Recall MATLAB struct syntax

   MATLAB uses struct('field1', value1, 'field2', value2) to create structures.

2. Step 2: Check each option's syntax

   person = struct('Name', 'Alice', 'Age', 30); uses correct parentheses and quotes. Options B, C, D use invalid syntax.

3. Final Answer:

   person = struct('Name', 'Alice', 'Age', 30); -> Option A

4. Quick Check:

   struct uses parentheses and quotes [OK]

Hint: Use parentheses and quotes with struct() [OK]

Common Mistakes:

• Using square or curly brackets instead of parentheses
• Omitting quotes around field names

3. What is the output of the following MATLAB code?

student(1).Name = 'John';
student(1).Score = 85;
student(2).Name = 'Jane';
student(2).Score = 92;
disp(student(2).Name);

medium

A. Jane

B. John

C. 85

D. 92

Solution

1. Step 1: Understand structure array indexing

   student(2) accesses the second element; .Name accesses the 'Name' field.

2. Step 2: Identify the value stored in student(2).Name

   It is 'Jane' as assigned in the code.

3. Final Answer:

   Jane -> Option A

4. Quick Check:

   student(2).Name = 'Jane' [OK]

Hint: Use index and field name to get value [OK]

Common Mistakes:

• Confusing index 1 and 2
• Accessing Score instead of Name

4. Identify the error in this MATLAB code snippet:

car.Make = 'Toyota';
car(1).Model = 'Corolla';
car(1).Year = 2020;

medium

A. Field names must be numeric

B. Missing semicolon after first line

C. Mixing scalar and array structure assignment causes error

D. No error, code runs fine

Solution

1. Step 1: Analyze structure assignment styles

   First line creates scalar structure car with field Make. Next lines assign to car(1), valid for scalar structures.

2. Step 2: Understand MATLAB structure array rules

   MATLAB allows indexing scalar structures and dynamically adding fields; no error occurs.

3. Final Answer:

   No error, code runs fine -> Option D

4. Quick Check:

   Scalar struct indexing + field addition works [OK]

Hint: Scalar structures can be indexed like arrays [OK]

Common Mistakes:

• Thinking scalar and array assignments cannot mix
• Believing field names must be numeric
• Assuming missing semicolons cause errors

5. Given a structure array books with fields Title and Pages, how do you create a new structure array shortBooks containing only books with less than 100 pages?

hard

A. shortBooks = books(books.Pages < 100);

B. shortBooks = books([books.Pages] < 100);

C. shortBooks = books{books.Pages < 100};

D. shortBooks = books(books.Pages > 100);

Solution

1. Step 1: Extract numeric array of Pages

   Use [books.Pages] to get all Pages values as a numeric array.

2. Step 2: Use logical indexing to filter

   Compare with < 100 to get logical indices, then index books with these.

3. Step 3: Check syntax correctness

   shortBooks = books([books.Pages] < 100); correctly uses parentheses and logical indexing; others are incorrect.

4. Final Answer:

   shortBooks = books([books.Pages] < 100); -> Option B

5. Quick Check:

   Logical indexing with [books.Pages] works [OK]

Hint: Use [struct.field] for numeric indexing [OK]

Common Mistakes:

• Using curly braces {} instead of parentheses ()
• Forgetting to use brackets [] around field extraction
• Using wrong comparison operator