Comparison operators in MATLAB - Mini Project: Build & Apply

Comparison operators

📖 Scenario: You are working in a store that sells fruits. You want to check which fruits have prices less than or equal to a certain budget.

🎯 Goal: Create a MATLAB script that uses comparison operators to find which fruits are affordable within a given budget.

📋 What You'll Learn

Create a dictionary (containers.Map) called fruitPrices with exact entries: 'apple' = 3, 'banana' = 1, 'cherry' = 5, 'date' = 2

Create a variable called budget and set it to 3

Use a for loop with variables fruit and price to iterate over fruitPrices.keys and check prices using comparison operators

Create a logical array called affordable that stores true for fruits with price less than or equal to budget

Print the names of fruits that are affordable using disp

💡 Why This Matters

🌍 Real World

Stores and shops often need to filter products based on price limits to help customers find affordable options.

💼 Career

Understanding comparison operators and data structures like dictionaries is essential for data filtering and decision-making in programming jobs.

1

Create the fruit prices dictionary

Create a containers.Map called fruitPrices with these exact entries: 'apple' = 3, 'banana' = 1, 'cherry' = 5, and 'date' = 2.

MATLAB

% Your code here

Hint

Use containers.Map with two cell arrays: one for keys and one for values.

2

Set the budget variable

Create a variable called budget and set it to 3.

MATLAB

fruitPrices = containers.Map({'apple', 'banana', 'cherry', 'date'}, [3, 1, 5, 2]);
% Your code here

Hint

Just assign the number 3 to the variable budget.

3

Check which fruits are affordable

Use a for loop with variable fruit to iterate over fruitPrices.keys. Inside the loop, get the price of each fruit from fruitPrices. Create a logical array called affordable that stores true if price is less than or equal to budget, otherwise false.

MATLAB

fruitPrices = containers.Map({'apple', 'banana', 'cherry', 'date'}, [3, 1, 5, 2]);
budget = 3;
% Your code here

Hint

Use fruitPrices.keys to get all fruits, then loop with an index. Compare each price with budget using <=.

4

Display affordable fruits

Use a for loop with index i to iterate over affordable. Inside the loop, if affordable(i) is true, use disp to print the fruit name from keysList{i}.

MATLAB

fruitPrices = containers.Map({'apple', 'banana', 'cherry', 'date'}, [3, 1, 5, 2]);
budget = 3;
keysList = fruitPrices.keys;
affordable = false(1, length(keysList));
for i = 1:length(keysList)
    fruit = keysList{i};
    price = fruitPrices(fruit);
    affordable(i) = (price <= budget);
end
% Your code here

Hint

Loop over affordable and print fruit names where the value is true.

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