Cell array creation in MATLAB - Mini Project: Build & Apply

Cell array creation

📖 Scenario: You are organizing a small collection of different types of data about fruits. You want to store their names, colors, and average weights together in a flexible container.

🎯 Goal: Create a cell array in MATLAB that holds the fruit names, their colors, and their average weights. Then, display the cell array.

📋 What You'll Learn

Create a cell array called fruits with exactly three rows and two columns.

The first row should contain the fruit names: 'Apple' and 'Banana'.

The second row should contain the colors: 'Red' and 'Yellow'.

The third row should contain the average weights in grams: 150 and 120.

Display the entire fruits cell array using disp.

💡 Why This Matters

🌍 Real World

Cell arrays let you store mixed data types together, like names, numbers, and descriptions, which is common in data analysis and reporting.

💼 Career

Knowing how to create and manipulate cell arrays is useful for engineers and scientists who work with diverse datasets in MATLAB.

1

Create the cell array fruits

Create a cell array called fruits with three rows and two columns. The first row should have 'Apple' and 'Banana'.

MATLAB

% Create the cell array fruits with fruit names in the first row
% Your code here

Hint

Use curly braces {} to create a cell array. Separate rows with semicolons ;.

2

Add colors to the second row

Add the colors 'Red' and 'Yellow' to the second row of the fruits cell array.

MATLAB

fruits = {'Apple', 'Banana'; '', '' ; '', ''};
% Add colors to the second row
% Your code here

Hint

Replace the empty strings in the second row with the color names.

3

Add average weights to the third row

Add the average weights 150 and 120 to the third row of the fruits cell array.

MATLAB

fruits = {'Apple', 'Banana'; 'Red', 'Yellow' ; '', ''};
% Add average weights to the third row
% Your code here

Hint

Replace the empty strings in the third row with the numeric weights.

4

Display the fruits cell array

Use disp(fruits) to display the entire fruits cell array.

MATLAB

fruits = {'Apple', 'Banana'; 'Red', 'Yellow' ; 150, 120};
% Display the fruits cell array
% Your code here

Hint

Use disp to show the contents of the cell array in the command window.

Practice

1. What is the correct way to create a cell array in MATLAB that contains a number, a string, and a logical value?

easy

A. myCell = [42, 'hello', true];

B. myCell = (42, 'hello', true);

C. myCell = {42, 'hello', true};

D. myCell = <42, 'hello', true>;

Solution

1. Step 1: Understand cell array syntax

   Cell arrays use curly braces { } to hold mixed data types.

2. Step 2: Identify correct syntax for mixed types

   myCell = {42, 'hello', true}; uses curly braces with different types: number, string, logical.

3. Final Answer:

   myCell = {42, 'hello', true}; -> Option C

4. Quick Check:

   Curly braces create cell arrays [OK]

Hint: Use curly braces { } for cell arrays, not square brackets [ ] [OK]

Common Mistakes:

• Using square brackets instead of curly braces
• Using parentheses instead of curly braces
• Using angle brackets which are invalid

2. Which of the following is the correct syntax to create a 2x2 cell array with elements 1, 'a', 3.14, and false?

easy

A. C = [1, 'a'; 3.14, false];

B. C = {1, 'a'; 3.14, false};

C. C = {1; 'a'; 3.14; false};

D. C = (1, 'a'; 3.14, false);

Solution

1. Step 1: Recall cell array 2D syntax

   Use curly braces { } with semicolons for rows and commas for columns.

2. Step 2: Check each option

   C = {1, 'a'; 3.14, false}; correctly uses { } with two rows and two columns separated by ; and ,.

3. Final Answer:

   C = {1, 'a'; 3.14, false}; -> Option B

4. Quick Check:

   Curly braces + semicolon for rows = correct 2D cell array [OK]

Hint: Use semicolon to separate rows inside curly braces [OK]

Common Mistakes:

• Using square brackets which create numeric arrays
• Using commas instead of semicolons for rows
• Using parentheses which are invalid for arrays

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

myCell = {10, 'MATLAB'; 'false', 3.5};
disp(myCell{2,1});

medium

A. false

B. 3.5

C. 'MATLAB'

D. 10

Solution

1. Step 1: Understand cell content access

   Using curly braces with indices accesses the content inside the cell.

2. Step 2: Identify the element at row 2, column 1

   myCell{2,1} is the element in second row, first column, which is 'false' as a string.

3. Final Answer:

   'false' -> Option A

4. Quick Check:

   myCell{2,1} = 'false' [OK]

Hint: Use curly braces { } to get cell content, not parentheses ( ) [OK]

Common Mistakes:

• Using parentheses instead of curly braces to access content
• Confusing row and column indices
• Expecting the whole cell instead of content

4. Consider this MATLAB code snippet:

C = {1, 2, 3; 4, 5, 6};
val = C(2,3);

What is the issue with this code if you want to get the number 6 as a value?

medium

A. C(2,3) returns a cell, not the content inside the cell

B. C(2,3) is invalid syntax for cell arrays

C. C(2,3) returns the number 6 directly

D. C(2,3) returns an error because of wrong indexing

Solution

1. Step 1: Understand difference between () and {}

   Parentheses () return a cell array subset, curly braces {} return content.

2. Step 2: Analyze C(2,3)

   C(2,3) returns a 1x1 cell containing 6, not the number 6 itself.

3. Final Answer:

   C(2,3) returns a cell, not the content inside the cell -> Option A

4. Quick Check:

   Use curly braces to get content: C{2,3} [OK]

Hint: Use curly braces { } to get cell content, parentheses () return cells [OK]

Common Mistakes:

• Using parentheses expecting content instead of cell
• Confusing cell array indexing with numeric array indexing
• Expecting direct numeric output from parentheses indexing

5. You want to create a cell array that stores a numeric vector, a string, and another cell array inside it. Which of the following correctly creates such a nested cell array?

hard

A. nestedCell = {[1, 2, 3], 'text', [true; false]};

B. nestedCell = {[1, 2, 3], 'text', [true, false]};

C. nestedCell = {[1, 2, 3], 'text', (true, false)};

D. nestedCell = {[1, 2, 3], 'text', {true, false}};

Solution

1. Step 1: Identify nested cell array syntax

   To nest a cell array inside another, use curly braces { } inside the main cell array.

2. Step 2: Check each option for correct nesting

   nestedCell = {[1, 2, 3], 'text', {true, false}}; uses {true, false} as a nested cell array inside the main cell array.

3. Final Answer:

   nestedCell = {[1, 2, 3], 'text', {true, false}}; -> Option D

4. Quick Check:

   Curly braces inside curly braces create nested cells [OK]

Hint: Use curly braces inside curly braces for nested cell arrays [OK]

Common Mistakes:

• Using square brackets for nested cell arrays
• Using parentheses which are invalid
• Using semicolons inside nested cell arrays incorrectly