Element-wise operations (.*, ./, .^) in MATLAB - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of element-wise multiplication

What is the output of the following MATLAB code?

MATLAB

A = [1 2 3];
B = [4 5 6];
C = A .* B;
disp(C);

A [4 10 18]

B [5 7 9]

C [4 5 6]

D [1 2 3 4 5 6]

💡 Hint

Remember that .* multiplies each element of A by the corresponding element of B.

The operator .* performs element-wise multiplication. So each element in A is multiplied by the corresponding element in B: 1*4=4, 2*5=10, 3*6=18.

❓ Predict Output

intermediate

Result of element-wise division

What will be displayed after running this MATLAB code?

MATLAB

X = [10 20 30];
Y = [2 4 5];
Z = X ./ Y;
disp(Z);

A [5 5 6.0000]

B [5 4 6]

C [5 5 6]

D [5 5 6.0]

💡 Hint

Element-wise division divides each element of X by the corresponding element of Y.

The operator ./ divides each element of X by the corresponding element of Y: 10/2=5, 20/4=5, 30/5=6.

❓ Predict Output

advanced

Output of element-wise power operation

What is the output of this MATLAB code snippet?

MATLAB

P = [2 3 4];
Q = [3 2 1];
R = P .^ Q;
disp(R);

A [6 5 4]

B [8 9 1]

C [8 6 4]

D [8 9 4]

💡 Hint

The .^ operator raises each element of P to the power of the corresponding element in Q.

Element-wise power means: 2^3=8, 3^2=9, 4^1=4. So the result is [8 9 4].

❓ Predict Output

advanced

Error type from wrong operator usage

What error does this MATLAB code produce?

MATLAB

A = [1 2 3];
B = [4 5 6];
C = A * B;

A Error: Undefined operator '*' for input arguments of type 'double'.

B Error: Inner matrix dimensions must agree.

C No error, output is [4 10 18].

D Error: Matrix dimensions must agree for element-wise multiplication.

💡 Hint

The * operator is matrix multiplication and requires matching inner dimensions.

A is 1x3 and B is 1x3, so their inner dimensions (3 and 1) do not match for matrix multiplication. MATLAB throws an error about inner matrix dimensions.

🧠 Conceptual

expert

Number of elements in result after element-wise operations

Given two matrices A (2x3) and B (2x3), what is the number of elements in the result of A .* B?

A 6

B 2

C 3

D 1

💡 Hint

Element-wise operations keep the same size as the input matrices.

Element-wise multiplication produces a matrix of the same size as the inputs. Since A and B are 2 rows by 3 columns, the result has 2*3=6 elements.