Character arrays and strings in MATLAB - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a character array named greeting with the text 'Hello'.

MATLAB

greeting = [1];

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

AHello

B"Hello"

C'Hello'

D[Hello]

Attempts:

3 left

💡 Hint

Common Mistakes

Using double quotes creates a string array, not a character array.

Not using quotes at all causes an error.

In MATLAB, character arrays are created using single quotes. So 'Hello' creates a character array.

2fill in blank

medium

Complete the code to concatenate two character arrays a and b into c.

MATLAB

a = 'Hi'; b = ' there'; c = a[1]b;

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

A+

B,

C''

D[]

Attempts:

3 left

💡 Hint

Common Mistakes

Using plus (+) operator which works for strings but not character arrays.

Using commas which cause syntax errors.

In MATLAB, concatenating character arrays is done by placing them inside square brackets [].

3fill in blank

hard

Fix the error in the code to convert a string s to a character array.

MATLAB

s = "Hello"; chars = [1](s);

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

Astring

Bchar

Ccellstr

DconvertCharsToStrings

Attempts:

3 left

💡 Hint

Common Mistakes

Using string() which converts character arrays to strings, not the other way.

Using cellstr() which converts to cell arrays.

The char() function converts a string to a character array in MATLAB.

4fill in blank

hard

Fill both blanks to create a character array of the first 3 letters of s.

MATLAB

s = 'MATLAB'; firstThree = s([1]:[2]);

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

A1

B3

C0

D4

Attempts:

3 left

💡 Hint

Common Mistakes

Using 0 as start index which is invalid in MATLAB.

Using 4 as end index which gets 4 letters instead of 3.

To get the first 3 letters, slice from index 1 to 3 in MATLAB.

5fill in blank

hard

Fill all three blanks to create a character array with uppercase letters from s and then find its length.

MATLAB

s = 'matlab'; upperS = [1](s); len = [2](upperS); disp([3]);

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

Aupper

Blength

Clen

Dnumel

Attempts:

3 left

💡 Hint

Common Mistakes

Using numel() instead of length() which also works but here length() is expected.

Trying to display upperS instead of the length variable.

Use upper() to convert to uppercase, length() to get length, and display the variable len.

Practice

1. Which of the following correctly creates a character array in MATLAB?

easy

A. name = [Hello];

B. name = "Hello";

C. name = 'Hello';

D. name = (Hello);

Solution

1. Step 1: Understand character array syntax

   Character arrays in MATLAB use single quotes to enclose text.

2. Step 2: Check each option

   name = 'Hello'; uses single quotes correctly. name = "Hello"; uses double quotes which create string objects, not character arrays. Options A and D are invalid syntax.

3. Final Answer:

   name = 'Hello'; -> Option C

4. Quick Check:

   Single quotes create character arrays [OK]

Hint: Use single quotes for character arrays, double for strings [OK]

Common Mistakes:

• Using double quotes for character arrays
• Missing quotes around text
• Using brackets or parentheses incorrectly

2. Which of the following is the correct way to create a string in MATLAB?

easy

A. str = "MATLAB";

B. str = 'MATLAB';

C. str = {"MATLAB"};

D. str = ("MATLAB");

Solution

1. Step 1: Recall string creation syntax

   Strings in MATLAB are created using double quotes.

2. Step 2: Evaluate options

   str = "MATLAB"; uses double quotes correctly. str = 'MATLAB'; creates a character array, not a string. Options C and D use invalid or different data types.

3. Final Answer:

   str = "MATLAB"; -> Option A

4. Quick Check:

   Double quotes create strings [OK]

Hint: Double quotes create strings, single quotes create char arrays [OK]

Common Mistakes:

• Confusing single and double quotes
• Using curly braces which create cell arrays
• Using parentheses incorrectly

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

charArray = 'abc';
str = "def";
disp([charArray str])

medium

A. abcdef

B. [abc def]

C. Error: Cannot concatenate char array and string

D. abc def

Solution

1. Step 1: Understand concatenation of char arrays and strings

   In MATLAB, concatenating a character array and a string with [] converts the string to a char array and joins them.

2. Step 2: Evaluate the concatenation result

   Concatenating 'abc' and "def" results in 'abcdef' as a character array, displayed without spaces.

3. Final Answer:

   abcdef -> Option A

4. Quick Check:

   Concatenation joins text without spaces [OK]

Hint: Concatenate char arrays and strings with [] to join text [OK]

Common Mistakes:

• Expecting spaces between concatenated strings
• Thinking concatenation causes error
• Confusing display output with variable type

4. Identify the error in the following MATLAB code:

str1 = 'Hello';
str2 = "World";
result = strcat(str1, str2);

medium

A. strcat cannot concatenate character arrays and strings

B. No error, code runs correctly

C. Missing semicolon after str2 assignment

D. str1 and str2 must both be strings or both char arrays

Solution

1. Step 1: Understand strcat behavior

   strcat can concatenate character arrays and strings by automatically converting strings to character arrays.

2. Step 2: Verify the code

   str1 is a character array, str2 is a string, but strcat(str1, str2) returns 'HelloWorld' as a character array. No error occurs.

3. Final Answer:

   No error, code runs correctly -> Option B

4. Quick Check:

   strcat handles mixed types [OK]

Hint: strcat automatically handles char and string inputs [OK]

Common Mistakes:

• Assuming strcat requires matching types
• Confusing with + operator which doesn't work for mixed types
• Looking for syntax errors where none exist

5. You have a character array chars = 'MATLAB' and want to convert it to a string and append " is fun". Which code correctly does this?

hard

A. newStr = chars + " is fun";

B. newStr = chars + ' is fun';

C. newStr = strcat(chars, " is fun");

D. newStr = string(chars) + " is fun";

Solution

1. Step 1: Convert character array to string

   Use string(chars) to convert the character array to a string type.

2. Step 2: Append text using + operator

   Strings can be concatenated with + and another string, so adding " is fun" works.

3. Step 3: Check other options

   newStr = chars + ' is fun'; tries to add char array and char array with + which is invalid. newStr = strcat(chars, " is fun"); mixes types but produces a character array, not a string. newStr = chars + " is fun"; adds char array and string with + which errors.

4. Final Answer:

   newStr = string(chars) + " is fun"; -> Option D

5. Quick Check:

   Convert char to string, then use + to join [OK]

Hint: Convert char array to string first, then use + to append [OK]

Common Mistakes:

• Using + to add char arrays
• Mixing char arrays and strings in strcat
• Not converting char array before concatenation