String vs character array in MATLAB - Practice Questions

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of string concatenation vs character array concatenation

What is the output of the following MATLAB code?

MATLAB

str1 = "Hello";
str2 = "World";
char1 = ['Hello'];
char2 = ['World'];

result1 = str1 + " " + str2;
result2 = [char1 ' ' char2];
disp(result1)
disp(result2)

A

HelloWorld
Hello World

B

Hello World
HelloWorld

C

Hello World
Hello World

D

Error
Hello World

💡 Hint

Remember that strings use + for concatenation, while character arrays use square brackets [].

In MATLAB, strings (double quotes) concatenate with + operator, adding spaces if included. Character arrays concatenate by placing them inside square brackets []. Both produce the same visible output when displayed.

❓ Predict Output

intermediate

Length difference between string and character array

What will be the output of the following MATLAB code?

MATLAB

str = "MATLAB";
charArr = ['M' 'A' 'T' 'L' 'A' 'B'];
lenStr = strlength(str);
lenChar = length(charArr);
disp(lenStr)
disp(lenChar)

A

7
6

B

6
6

C

6
7

D

Error
6

💡 Hint

Check how strlength and length functions behave on strings and character arrays.

strlength returns the number of characters in a string. length returns the number of elements in an array. Both return 6 here.

🔧 Debug

advanced

Identify the error when mixing string and character array

What error does the following MATLAB code produce?

MATLAB

str = "Data";
charArr = ['S' 'c' 'i' 'e' 'n' 'c' 'e'];
result = str + charArr;

A Error: Undefined operator '+' for input arguments of type 'string' and 'char'.

B DataScience

C Data Science

D Error: Matrix dimensions must agree.

💡 Hint

Consider the types of variables and what + operator supports.

MATLAB does not allow + operator between a string and a character array. This causes an undefined operator error.

🧠 Conceptual

advanced

Difference in indexing between string and character array

Consider the following MATLAB code:

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

char1 = str(2);
char2 = charArr(2);

What are the values of char1 and char2?

A char1 is a string "e"; char2 is a character 'e'

B char1 is a character 'e'; char2 is a string "e"

C char1 is a string "el"; char2 is a character 'e'

D char1 is a character 'e'; char2 is a character 'l'

💡 Hint

Remember that indexing a string returns a string scalar, indexing a character array returns a char.

Indexing a string returns a string scalar (still double quotes). Indexing a character array returns a single character (single quotes).

❓ Predict Output

expert

Behavior of strcmp with string and character array

What is the output of this MATLAB code?

MATLAB

str = "Test";
charArr = ['T' 'e' 's' 't'];
result = strcmp(str, charArr);
disp(result)

A Error: Inputs must be character arrays or cell arrays of character vectors.

B 0

C Error: Undefined function 'strcmp' for input arguments of type 'string' and 'char'.

D 1

💡 Hint

Check if strcmp supports comparing string and character array.

strcmp converts string inputs to character arrays internally and compares them correctly, returning 1 for equality.

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