Logical values in MATLAB - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a logical true value.

MATLAB

x = [1];

Drag options to blanks, or click blank then click option'

Atrue

B1

Cfalse

D0

Attempts:

3 left

💡 Hint

Common Mistakes

Using numeric 1 instead of logical true

Using false or 0 which represent logical false

In MATLAB, true is the logical value for true.

2fill in blank

medium

Complete the code to check if variable a is greater than 5.

MATLAB

result = (a [1] 5);

Drag options to blanks, or click blank then click option'

A>

B<

C==

D~=

Attempts:

3 left

💡 Hint

Common Mistakes

Using < instead of >

Using == which checks equality

The operator > checks if a is greater than 5, returning a logical value.

3fill in blank

hard

Fix the error in the code to correctly assign a logical false value.

MATLAB

flag = [1];

Drag options to blanks, or click blank then click option'

A0

Bfalse

CFalse

DFalse()

Attempts:

3 left

💡 Hint

Common Mistakes

Using capitalized False which is invalid

Using 0 which is numeric, not logical false

MATLAB uses lowercase false to represent logical false.

4fill in blank

hard

Fill both blanks to create a logical array with true and false values.

MATLAB

arr = [[1], [2]];

Drag options to blanks, or click blank then click option'

Atrue

Bfalse

C1

D0

Attempts:

3 left

💡 Hint

Common Mistakes

Using numeric 1 and 0 instead of logical true and false

Mixing uppercase and lowercase keywords

The array contains logical true and false values.

5fill in blank

hard

Fill all three blanks to create a logical vector where elements are true if x is greater than 3, less than 7, and not equal to 5.

MATLAB

result = (x [1] 3) & (x [2] 7) & (x [3] 5);

Drag options to blanks, or click blank then click option'

A>

B<

C==

D~=

Attempts:

3 left

💡 Hint

Common Mistakes

Using == instead of ~=

Mixing up > and < operators

The expression checks if x is greater than 3, less than 7, and not equal to 5, returning logical values.

Practice

1. What is the result of the expression 5 > 3 in MATLAB?

easy

A. 5

B. false

C. 3

D. true

Solution

1. Step 1: Understand the comparison operator

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

2. Step 2: Compare the numbers 5 and 3

   Since 5 is greater than 3, the expression returns true.

3. Final Answer:

   true -> Option D

4. Quick Check:

   5 > 3 = true [OK]

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

Common Mistakes:

• Confusing true with the number 5
• Thinking it returns the bigger number
• Mixing up > and < operators

2. Which of the following is the correct way to create a logical true value in MATLAB?

easy

A. 1 == 1

B. 1 = 1

C. logical(0)

D. true

Solution

1. Step 1: Evaluate each option

   logical(0) returns false.
   1 = 1 causes syntax error (cannot assign to constant).
   true errors (function requires arguments like true()).
   1 == 1 returns true.

2. Step 2: Identify the working method

   Only 1 == 1 correctly creates a logical true value.

3. Final Answer:

   1 == 1 -> Option A

4. Quick Check:

   1 == 1 = true [OK]

Hint: Use == in comparisons to get logical true [OK]

Common Mistakes:

• logical(0) returns false
• Using = instead of == for comparison
• Omitting () on true()

3. What is the output of this MATLAB code?

val = (4 < 2) | (7 == 7);
disp(val);

medium

A. Error

B. 0

C. 1

D. [0 1]

Solution

1. Step 1: Evaluate each logical expression

   4 < 2 is false (0), 7 == 7 is true (1).

2. Step 2: Apply the OR operator (|)

   False OR True results in true (1).

3. Final Answer:

   1 -> Option C

4. Quick Check:

   (false OR true) = true = 1 [OK]

Hint: OR is true if any side is true [OK]

Common Mistakes:

• Confusing OR (|) with AND (&)
• Expecting vector output
• Misreading comparison operators

4. Identify the error in this MATLAB code:

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

medium

A. Using single = instead of == in if condition

B. Missing semicolon after disp statement

C. Incorrect use of disp function

D. No error, code runs fine

Solution

1. Step 1: Check the if condition syntax

   The single equal sign = is for assignment, not comparison.

2. Step 2: Correct the comparison operator

   Use double equal signs == to compare values in conditions.

3. Final Answer:

   Using single = instead of == in if condition -> Option A

4. Quick Check:

   Comparison needs ==, not = [OK]

Hint: Use == for comparison, = for assignment [OK]

Common Mistakes:

• Using = in if condition
• Ignoring MATLAB error messages
• Assuming semicolon is mandatory after disp

5. Given the vector A = [-1 0 1 2 0], which MATLAB expression returns a logical vector indicating which elements are nonzero?

hard

A. All of the above

B. A ~= 0

C. A > 0

D. A != 0

Solution

1. Step 1: Understand each expression

   A ~= 0 returns true where not zero.
   A != 0 uses invalid != operator (use ~=).
   A > 0 true only for positives.

2. Step 2: Check which elements each marks true for A = [-1 0 1 2 0]

   - A ~= 0: [true, false, true, true, false]
   - A != 0: syntax error
   - A > 0: [false, false, true, true, false]

3. Final Answer:

   A ~= 0 -> Option B

4. Quick Check:

   A ~= 0 = nonzero logical vector [OK]

Hint: Use ~= 0 to find nonzero elements [OK]

Common Mistakes:

• Using != instead of ~=
• Confusing ~= with ==
• Assuming >0 misses negative nonzero