Character arrays and strings in MATLAB - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the difference between a character array and a string in MATLAB?

A character array is a sequence of characters stored as a 2D array of type char. A string is a MATLAB string object created with double quotes, which offers more functions and easier manipulation.

beginner

How do you create a character array and a string in MATLAB?

Character array: charArray = ['H', 'e', 'l', 'l', 'o'];
String: str = "Hello";

beginner

How can you concatenate two strings in MATLAB?

Use the + operator for strings: str1 + str2. For character arrays, use [charArray1, charArray2].

intermediate

What function converts a string to a character array in MATLAB?

Use the char() function. For example, charArray = char(str); converts string str to a character array.

beginner

How do you find the length of a string or character array in MATLAB?

Use strlength() for strings and length() or size() for character arrays. Example: strlength(str) or length(charArray).

Which of the following creates a string in MATLAB?

A str = "Hello";

B str = ['H', 'e', 'l', 'l', 'o'];

C str = {"Hello"};

D str = ('Hello');

Strings in MATLAB are created using double quotes, like "Hello".

How do you concatenate two character arrays c1 and c2?

A [c1, c2]

B strcat(c1, c2)

C c1 + c2

D append(c1, c2)

Concatenate character arrays by placing them inside square brackets: [c1, c2].

What does strlength("MATLAB") return?

A Error

B 6

C 0

D 1

strlength returns the number of characters in the string, which is 6 for "MATLAB".

Which function converts a string to a character array?

A convert()

B string()

C char()

D array()

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

What is the output of class('Hello') in MATLAB?

A "string"

B "double"

C "cell"

D "char"

Single quotes create a character array of class char.

Explain how to create, concatenate, and find the length of strings and character arrays in MATLAB.

Think about the differences in syntax and functions for strings vs character arrays.

Describe how to convert between strings and character arrays in MATLAB and why you might want to do that.

Consider the advantages of each type and compatibility with MATLAB functions.

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