Cell array creation in MATLAB - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a 1x3 cell array named C.

MATLAB

C = [1](1,3);

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

Alist

Barray

Cmatrix

Dcell

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'array' or 'matrix' instead of 'cell' to create cell arrays.

Trying to create cell arrays with square brackets.

The function 'cell' creates a cell array of specified size in MATLAB.

2fill in blank

medium

Complete the code to assign the string 'hello' to the first cell of cell array C.

MATLAB

C[1] = 'hello';

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

A{1}

B[1]

C(1)

D(1,1)

Attempts:

3 left

💡 Hint

Common Mistakes

Using parentheses or square brackets instead of curly braces for cell content assignment.

Using multiple indices when only one is needed for a 1D cell array.

Use curly braces { } to access or assign contents of a cell in MATLAB.

3fill in blank

hard

Fix the error in the code to create a 2x2 cell array with numbers 1 to 4 inside.

MATLAB

C = [1](2,2);
C[2] = 1;
C[3] = 2;
C[4] = 3;
C[5] = 4;

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

Acell

B(1,1)

C{1,1}

D(1)

E{1}

F(1,2)

G{1,2}

H(2,1)

I{2,1}

J(2,2)

K{2,2}

Attempts:

3 left

💡 Hint

Common Mistakes

Using parentheses instead of curly braces for cell content assignment.

Using single index for 2D cell array assignment.

Use 'cell' to create the array. Use curly braces with row and column indices to assign values inside cells.

4fill in blank

hard

Fill both blanks to create a cell array with mixed types: a string and a numeric array.

MATLAB

C = [1](1,2);
C[2] = 'text';

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

Acell

B{1,1}

C{1,2}

D(1,2)

Attempts:

3 left

💡 Hint

Common Mistakes

Using parentheses instead of curly braces for assignment.

Using wrong indices for the cell assignment.

Use 'cell(1,2)' to create the cell array. Assign the string to the first cell using curly braces with indices.

5fill in blank

hard

Fill all three blanks to create a 2x2 cell array and assign a string, a number, and a vector to different cells.

MATLAB

C = [1](2,2);
C[2] = 'hello';
C[3] = 42;
C{2,2} = [1, 2, 3];

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

Acell

B{1,1}

C{1,2}

D{2,1}

Attempts:

3 left

💡 Hint

Common Mistakes

Using parentheses instead of curly braces for assignment.

Mixing up the indices for cell assignment.

Create the cell array with 'cell(2,2)'. Assign 'hello' to C{1,1} and 42 to C{2,1}. The vector is assigned to C{2,2}.

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