String vs character array in MATLAB

Introduction

Strings and character arrays both store text in MATLAB, but they work differently. Knowing the difference helps you choose the right one for your task.

When you want to store and manipulate text easily with built-in functions, use strings.

When you need to work with older MATLAB code that uses character arrays.

When you want to treat text as a sequence of characters, use character arrays.

When you want to combine or compare text data simply, strings are easier.

When you want to access or change individual characters, character arrays can be helpful.

Syntax

MATLAB

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

Strings are created with double quotes " ".

Character arrays use single quotes ' ' around each character or a single quoted sequence.

Examples

This creates a string and displays it.

MATLAB

str = "Hello, world!";
disp(str);

This creates a character array and displays it.

MATLAB

charArray = ['H', 'e', 'l', 'l', 'o'];
disp(charArray);

Shows empty string and empty character array.

MATLAB

emptyStr = "";
emptyCharArray = '';
disp(emptyStr);
disp(emptyCharArray);

Single character string vs single character array.

MATLAB

singleCharStr = "A";
singleCharArray = 'A';
disp(singleCharStr);
disp(singleCharArray);

Sample Program

This program shows how to create a string and a character array, access their first characters, and modify the second character in both.

MATLAB

str = "Hello";
charArray = ['H', 'e', 'l', 'l', 'o'];

fprintf('String: %s\n', str);
fprintf('Character array: %s\n', charArray);

% Access first character
fprintf('First character of string: %s\n', str(1));
fprintf('First character of char array: %s\n', charArray(1));

% Modify second character
str(2) = 'a';
charArray(2) = 'a';

fprintf('Modified string: %s\n', str);
fprintf('Modified char array: %s\n', charArray);

Important Notes

Strings are easier to work with for most text operations because MATLAB has many built-in string functions.

Character arrays are older and sometimes needed for compatibility with legacy code.

Strings use more memory but offer more features like string arrays and text processing.

Summary

Strings use double quotes and are modern, flexible text containers.

Character arrays use single quotes and treat text as a list of characters.

Choose strings for new code and character arrays for legacy or specific character-level tasks.

Practice

1. Which of the following correctly represents a string in MATLAB?

easy

A. 'Hello World'

B. ('Hello World')

C. {'Hello World'}

D. "Hello World"

Solution

1. Step 1: Understand string syntax in MATLAB

   Strings in MATLAB are enclosed in single quotes, like 'Hello World'.

2. Step 2: Identify string and character array syntax

   In MATLAB, single quotes denote character arrays (which are often used as strings). Double quotes denote string arrays introduced in newer MATLAB versions, but the classic string representation is single quotes.

3. Final Answer:

   'Hello World' -> Option A

4. Quick Check:

   Single quotes denote character arrays (strings) = B [OK]

Hint: Strings use single quotes in MATLAB [OK]

Common Mistakes:

• Confusing single quotes for strings
• Using curly braces which create cell arrays
• Using parentheses which are invalid for strings

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

easy

A. charArray = "abc";

B. charArray = ["a", "b", "c"];

C. charArray = { 'a', 'b', 'c' };

D. charArray = 'abc';

Solution

1. Step 1: Recognize character array syntax

   Character arrays are created using single quotes around text, like 'abc'.

2. Step 2: Differentiate from string and cell array

   Double quotes create string arrays, and curly braces create cell arrays, so only single quotes create character arrays.

3. Final Answer:

   charArray = 'abc'; -> Option D

4. Quick Check:

   Character arrays use single quotes = C [OK]

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

Common Mistakes:

• Using double quotes for character arrays
• Using curly braces which create cell arrays
• Using square brackets with commas incorrectly

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

str = "MATLAB";
charArr = 'MATLAB';
disp(class(str));
disp(class(charArr));

medium

A. string
char

B. char
string

C. string
string

D. char
char

Solution

1. Step 1: Identify variable types

   Variable str is created with double quotes, so it is a string type. Variable charArr uses single quotes, so it is a character array (char).

2. Step 2: Understand class() output

   The class() function returns the type name as a string. So class(str) returns 'string' and class(charArr) returns 'char'.

3. Final Answer:

   string char -> Option A

4. Quick Check:

   Double quotes = string, single quotes = char [OK]

Hint: class() shows 'string' for double quotes, 'char' for single quotes [OK]

Common Mistakes:

• Assuming both are 'char' type
• Confusing output order
• Thinking class() returns variable content

4. Consider this MATLAB code snippet:

str = 'Hello';
str(1) = "h";

What is the error in this code?

medium

A. Indexing starts at 0, so str(1) is invalid

B. Cannot assign double quotes to a character array element

C. Strings cannot be indexed like arrays

D. No error, code runs fine

Solution

1. Step 1: Identify variable type

   Variable str is created with single quotes, so it is a character array.

2. Step 2: Understand assignment rules for character arrays

   Character array elements must be assigned single characters using single quotes. Assigning a double-quoted string "h" causes a type mismatch error.

3. Final Answer:

   Cannot assign double quotes to a character array element -> Option B

4. Quick Check:

   Character arrays need single quotes for elements [OK]

Hint: Assign single characters with single quotes to char arrays [OK]

Common Mistakes:

• Using double quotes to assign char array elements
• Thinking MATLAB indexing starts at 0
• Assuming strings can't be indexed

5. You want to concatenate the words "Data" and 'Science' in MATLAB to form a string. Which code correctly does this and results in a string type?

hard

A. result = "Data" + 'Science';

B. result = "Data" + "Science";

C. result = "Data" + string('Science');

D. result = "Data" + char('Science');

Solution

1. Step 1: Understand types of inputs

   "Data" is a string. 'Science' is a character array. To concatenate strings, both must be string type.

2. Step 2: Convert character array to string before concatenation

   Using string('Science') converts the char array to string, allowing + operator to concatenate strings properly.

3. Final Answer:

   result = "Data" + string('Science'); -> Option C

4. Quick Check:

   Convert char to string before + concatenation [OK]

Hint: Convert char arrays to strings before using + for concatenation [OK]

Common Mistakes:

• Trying to add string and char directly
• Using + with char arrays (causes error)
• Not converting char to string before concatenation