Special matrices (zeros, ones, eye, rand) in MATLAB - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of zeros and ones matrix operations

What is the output of the following MATLAB code?

 A = zeros(2,3);
 B = ones(3,2);
 C = A * B;
 disp(C);

MATLAB

A = zeros(2,3);
B = ones(3,2);
C = A * B;
disp(C);

A [1 1; 1 1]

B [3 3; 3 3]

C Error: Matrix dimensions must agree.

D [0 0; 0 0]

💡 Hint

Remember that zeros multiplied by any number results in zeros.

Matrix A is 2x3 zeros, B is 3x2 ones. Multiplying zeros by ones results in a 2x2 zero matrix.

❓ Predict Output

intermediate

Eye matrix diagonal values

What does the following MATLAB code display?

 I = eye(4);
 disp(I(2,2));
 disp(I(2,3));

MATLAB

I = eye(4);
disp(I(2,2));
disp(I(2,3));

A

0
1

B

1
1

C

1
0

D

0
0

💡 Hint

Eye matrix has ones on the diagonal and zeros elsewhere.

I(2,2) is on the diagonal, so it is 1. I(2,3) is off-diagonal, so it is 0.

🔧 Debug

advanced

Identify the error in matrix creation

What error does this MATLAB code produce?

 M = zeros(3);
 N = ones(2,3);
 P = M + N;

MATLAB

M = zeros(3);
N = ones(2,3);
P = M + N;

A No error, P is a 3x3 matrix of ones.

B Error: Matrix dimensions must agree.

C Error: Undefined function or variable 'P'.

D No error, P is a 2x3 matrix of zeros.

💡 Hint

Check the sizes of M and N before adding.

M is 3x3, N is 2x3, so addition is invalid due to dimension mismatch.

❓ Predict Output

advanced

Random matrix value range

What is the range of values produced by this MATLAB code?

 R = rand(2,2);
 disp(min(R(:)));
 disp(max(R(:)));

MATLAB

R = rand(2,2);
disp(min(R(:)));
disp(max(R(:)));

A Values between 0 and 1, exclusive

B Values between 0 and 1, inclusive

C Values between -1 and 1

D Values between 1 and 2

💡 Hint

rand generates numbers in the interval (0,1).

rand produces uniformly distributed random numbers strictly greater than 0 and less than 1.

🧠 Conceptual

expert

Number of elements in special matrices

How many elements does the matrix created by eye(5,3) contain in MATLAB?

A 15

B 5

C 3

D 8

💡 Hint

Count total elements in a 5-by-3 matrix.

eye(5,3) creates a 5 rows by 3 columns matrix, so total elements = 5*3 = 15.