Matrix creation in MATLAB - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this matrix creation code?

Consider the following MATLAB code that creates a matrix. What will be the resulting matrix?

MATLAB

A = zeros(2,3) + eye(2,3); disp(A);

A [0 0 0; 0 0 0]

B [1 0; 0 1; 0 0]

C [1 0 0; 0 1 0]

D [1 1 1; 1 1 1]

💡 Hint

Remember that eye(m,n) creates an m-by-n matrix with ones on the main diagonal and zeros elsewhere.

The zeros(2,3) creates a 2-by-3 matrix of zeros. The eye(2,3) creates a 2-by-3 identity-like matrix with ones on the diagonal. Adding them results in a matrix with ones on the diagonal and zeros elsewhere.

❓ Predict Output

intermediate

What is the size of the matrix created?

What is the size of the matrix B created by this MATLAB code?

MATLAB

B = ones(4) * 5;

A 4x4

B 5x5

C 4x1

D 1x4

💡 Hint

ones(n) creates an n-by-n matrix of ones.

The ones(4) creates a 4-by-4 matrix of ones. Multiplying by 5 scales every element but does not change the size.

❓ Predict Output

advanced

What does this matrix creation code output?

What is the output of this MATLAB code snippet?

MATLAB

C = diag([3 4 5]); disp(C);

A [3 0 0; 4 0 0; 5 0 0]

B [3 4 5; 0 0 0; 0 0 0]

C [0 3 0; 0 4 0; 0 0 5]

D [3 0 0; 0 4 0; 0 0 5]

💡 Hint

The diag function creates a diagonal matrix from the input vector.

diag([3 4 5]) creates a square matrix with 3, 4, and 5 on the main diagonal and zeros elsewhere.

❓ Predict Output

advanced

What is the output of this matrix concatenation?

What matrix does this MATLAB code produce?

MATLAB

D = [1 2; 3 4]; E = [5 6; 7 8]; F = [D E; E D]; disp(F);

A [1 2 5 6; 3 4 7 8; 5 6 1 2; 7 8 3 4]

B [1 2 3 4; 5 6 7 8; 1 2 3 4; 5 6 7 8]

C [1 2 5 6; 3 4 7 8; 1 2 5 6; 3 4 7 8]

D [5 6 1 2; 7 8 3 4; 1 2 5 6; 3 4 7 8]

💡 Hint

Square brackets concatenate matrices horizontally and vertically.

The code concatenates D and E horizontally to form the top half, and E and D horizontally to form the bottom half, then concatenates these vertically.

❓ Predict Output

expert

What is the output of this complex matrix creation code?

What is the output of this MATLAB code snippet?

MATLAB

G = repmat([1 2; 3 4], 2, 3); disp(G);

A [1 2 1 2; 3 4 3 4; 1 2 1 2; 3 4 3 4]

B [1 2 1 2 1 2; 3 4 3 4 3 4; 1 2 1 2 1 2; 3 4 3 4 3 4]

C [1 2 3 4 1 2; 3 4 1 2 3 4; 1 2 3 4 1 2; 3 4 1 2 3 4]

D [1 2 3 4 5 6; 7 8 9 10 11 12; 1 2 3 4 5 6; 7 8 9 10 11 12]

💡 Hint

repmat repeats the matrix the specified number of times in rows and columns.

repmat([1 2; 3 4], 2, 3) repeats the 2x2 matrix 2 times vertically and 3 times horizontally, resulting in a 4x6 matrix.