Comparison operators in MATLAB

Introduction

Comparison operators help you check if values are equal, bigger, or smaller. They let your program make decisions based on these checks.

To check if a number is greater than another before doing a calculation.

To find out if two values are the same, like passwords or answers.

To run code only when a condition is true, like if a score is above a limit.

To compare elements in arrays and get true or false results for each.

To filter data by checking which values meet certain criteria.

Syntax

MATLAB

a == b  % equal to
 a ~= b  % not equal to
 a > b   % greater than
 a < b   % less than
 a >= b  % greater than or equal to
 a <= b  % less than or equal to

Use double equals (==) to check if two values are equal, not a single equals (=) which assigns values.

Comparison operators return logical true (1) or false (0) in MATLAB.

Examples

Checks if 5 is equal to 5. Result is true (1).

MATLAB

5 == 5

Checks if 3 is not equal to 4. Result is true (1).

MATLAB

3 ~= 4

Checks if 7 is greater than 10. Result is false (0).

MATLAB

7 > 10

Checks each element if it is less than or equal to 2. Result is [1 1 0].

MATLAB

[1 2 3] <= 2

Sample Program

This program compares two numbers a and b. It prints if a is greater than b. Then it checks if a equals b and shows the answer.

MATLAB

a = 8;
b = 5;

if a > b
    disp('a is greater than b')
else
    disp('a is not greater than b')
end

result = (a == b);
disp(['Is a equal to b? ', num2str(result)])

Important Notes

Remember that == checks equality, while = assigns values.

Logical results can be used directly in if statements to control program flow.

When comparing arrays, MATLAB returns an array of logicals for each element.

Summary

Comparison operators let you compare values to make decisions.

They return true (1) or false (0) in MATLAB.

Use them in conditions like if statements or to compare arrays element-wise.

Practice

1. What does the MATLAB expression 5 > 3 return?

easy

A. 0 (false)

B. 1 (true)

C. Error

D. 5

Solution

1. Step 1: Understand the comparison operator

   The operator > checks if the left value is greater than the right value.

2. Step 2: Compare the values 5 and 3

   Since 5 is greater than 3, the expression returns true, which is represented as 1 in MATLAB.

3. Final Answer:

   1 (true) -> Option B

4. Quick Check:

   5 > 3 = 1 [OK]

Hint: Greater than means left number bigger than right [OK]

Common Mistakes:

• Confusing true (1) with false (0)
• Thinking it returns the bigger number
• Using wrong operator like < instead of >

2. Which of the following is the correct MATLAB syntax to check if variable a is equal to 10?

easy

A. a = 10

B. a === 10

C. a != 10

D. a == 10

Solution

1. Step 1: Identify the equality operator in MATLAB

   MATLAB uses double equal signs == to test equality, not a single equal sign.

2. Step 2: Check each option

   a = 10 assigns 10 to a, not compare. a == 10 correctly compares a to 10. a === 10 uses triple equals which is invalid in MATLAB. a != 10 uses not equal operator incorrectly.

3. Final Answer:

   a == 10 -> Option D

4. Quick Check:

   Equality test uses == [OK]

Hint: Use double equals (==) to compare, single equals (=) assigns [OK]

Common Mistakes:

• Using single = instead of ==
• Using === which is not MATLAB syntax
• Confusing != with ~= for not equal

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

a = [1 3 5]; b = [2 3 4]; result = a <= b;

medium

A. [1 1 0]

B. [1 0 0]

C. [0 1 1]

D. [0 0 1]

Solution

1. Step 1: Understand element-wise comparison

   The operator <= compares each element of a with the corresponding element of b.

2. Step 2: Compare each pair

   1 <= 2 is true (1), 3 <= 3 is true (1), 5 <= 4 is false (0).

3. Final Answer:

   [1 1 0] -> Option A

4. Quick Check:

   Element-wise <= comparison = [1 1 0] [OK]

Hint: Compare arrays element-wise for <= operator [OK]

Common Mistakes:

• Thinking it returns a single value
• Mixing up < and <= operators
• Forgetting element-wise comparison

4. Identify the error in this MATLAB code snippet:

if a = 5
    disp('Equal');
end

medium

A. Missing semicolon after assignment

B. disp function is incorrect

C. Using = instead of == in if condition

D. if statement needs parentheses

Solution

1. Step 1: Check the if condition syntax

   In MATLAB, the if condition requires a logical expression, not an assignment.

2. Step 2: Identify the operator mistake

   The code uses = which assigns 5 to a, instead of == which compares a to 5.

3. Final Answer:

   Using = instead of == in if condition -> Option C

4. Quick Check:

   Comparison uses ==, not = in conditions [OK]

Hint: Use == for comparison inside if, not = [OK]

Common Mistakes:

• Using = instead of ==
• Adding unnecessary parentheses
• Misusing disp function

5. Given two arrays A = [4 7 2 9] and B = [5 7 3 8], write a MATLAB expression using comparison operators to create a logical array that is true where elements of A are greater than or equal to B and false otherwise. What is the resulting array?

hard

A. [0 1 0 1]

B. [1 1 1 1]

C. [0 0 0 0]

D. [1 0 1 0]

Solution

1. Step 1: Use element-wise comparison operator

   Use the operator >= to compare each element of A with B element-wise.

2. Step 2: Compare each element pair

   4 >= 5 is false (0), 7 >= 7 is true (1), 2 >= 3 is false (0), 9 >= 8 is true (1).

3. Final Answer:

   [0 1 0 1] -> Option A

4. Quick Check:

   A >= B = [0 1 0 1] [OK]

Hint: Use >= for element-wise greater or equal comparison [OK]

Common Mistakes:

• Using > instead of >=
• Confusing logical array with numeric values
• Mixing element-wise with matrix operations