FREE MATLAB Matrix and Array Operations Questions and Answers

Question 1

Given two 3x3 matrices, A and B, which MATLAB command will perform element-wise multiplication?

Accepted Answer

A .* B

Answer

A * B

Answer

A x B

Answer

multiply(A, B)

Question 2

A user has a matrix `M = [10, 25, 15; 30, 5, 20];`. Which command will return a column vector containing only the elements of `M` that are greater than 15?

Accepted Answer

M(M > 15)

Answer

find(M > 15)

Answer

M > 15

Answer

extract(M, M > 15)

Question 3

A user wants to create a new 4x3 matrix by vertically stacking a 2x3 matrix `A` on top of another 2x3 matrix `B`. Which of the following commands will accomplish this?

Accepted Answer

[A; B]

Answer

[A, B]

Answer

[A B]

Answer

cat(A, B)

Question 4

Given a complex matrix `C = [1+2i, 3-1i; 4, 5+6i]`, what is the result of the command `C.'`?

Accepted Answer

It computes the non-conjugate transpose.

Answer

It computes the complex conjugate transpose.

Answer

It results in an error because the matrix is complex.

Answer

It calculates the inverse of the matrix.

Question 5

What is the key difference between the `length(M)` and `numel(M)` functions for a non-vector matrix `M` (e.g., a 3x5 matrix)?

Accepted Answer

`length(M)` returns the size of the largest dimension, while `numel(M)` returns the total number of elements.

Answer

`length(M)` returns the number of columns, while `numel(M)` returns the number of rows.

Answer

`length(M)` returns the total number of elements, while `numel(M)` returns the largest dimension.

Answer

Both functions return the total number of elements and are interchangeable.

Question 6

A user executes the following code:

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

What are the dimensions of the resulting matrix `C`?

Accepted Answer

2x1

Answer

2x2

Answer

1x2

Answer

An error occurs.