MATLAB Practice Test Video Answers

1. B
Row vectors in MATLAB are created using square brackets with elements
separated by commas or spaces. Semicolons create column vectors, curly
braces create cell arrays, and parentheses are used for indexing, not
array creation.

2. B
The .* operator performs element-wise multiplication where corresponding
elements are multiplied. The * operator without the dot performs standard
matrix multiplication following linear algebra rules.

3. A
MATLAB uses (row, column) indexing. The notation A(2:4, 3) selects rows
2 through 4 from column 3, returning a 3×1 column vector containing
three elements.

4. C
The size() function returns the dimensions of a matrix as .
The length() function returns only the largest dimension, while dim()
and sizeof() are not standard MATLAB functions.

5. B
The ^ operator performs exponentiation in MATLAB. Therefore, 5^2
calculates 5 raised to the power of 2, which equals 25.

6. B
The command “clear all” removes all variables from the workspace memory.
This is useful for starting fresh or freeing up memory during long
computational sessions.

7. B
The colon operator with three arguments (start:step:end) creates a
sequence. Here, 1:2:9 starts at 1, increments by 2, and stops at or
before 9, producing [1, 3, 5, 7, 9].

8. D
Both inv(A) and A^(-1) compute the matrix inverse in MATLAB. The inv()
function is the explicit inverse function, while A^(-1) uses matrix
power operation to achieve the same result.

9. B
The eye(n) function creates an n×n identity matrix with ones on the
main diagonal and zeros elsewhere. eye(3) creates a 3×3 identity matrix.

10. C
The semicolon (;) at the end of a statement suppresses the output
display in the Command Window. This is useful for preventing clutter
when executing many commands.

11. C
The zeros(m,n) function creates an m×n matrix filled with zeros.
Therefore, zeros(2,3) creates a 2-row by 3-column matrix of zeros.

12. B
The eig() function computes eigenvalues and optionally eigenvectors
of a square matrix. It is the standard MATLAB function for eigenvalue
decomposition.

13. C
MATLAB FOR loops use the syntax “for variable = expression” where the
expression typically uses the colon operator. The loop iterates through
each value in the expression.

14. B
The numel() function returns the total number of elements in an array,
regardless of its dimensions. It is equivalent to prod(size(A)) for
any array A.

15. B
The single quote operator (‘) computes the conjugate transpose
(Hermitian transpose) of a matrix. For real matrices, this is
equivalent to the standard transpose.

16. C
The rand() function generates uniformly distributed random numbers
between 0 and 1. The randn() function generates normally distributed
random numbers with mean 0 and variance 1.

17. B
MATLAB functions are defined using the keyword “function” followed by
output variables, the equals sign, function name, and input arguments
in parentheses.

18. A
The forward slash (/) performs matrix right division, solving xA = B.
The backslash () performs left division, solving Ax = B. The dot
operators (./ and .) perform element-wise division.

19. B
The linspace(a, b, n) function creates n linearly spaced points between
a and b, inclusive. linspace(0, 10, 5) creates 5 points: [0, 2.5, 5,
7.5, 10].

20. B
The title() function adds a title string above the current axes in a
figure. It accepts a string argument that becomes the plot title.

21. B
The mod(a, b) function returns the remainder after division of a by b.
mod(17, 5) = 17 – 5*floor(17/5) = 17 – 5*3 = 17 – 15 = 2.

22. B
The horzcat() function concatenates arrays horizontally (along columns).
This is equivalent to using square brackets: . vertcat() or
concatenates vertically.

23. B
When the input is a vector, diag(v) creates a square diagonal matrix
with the vector elements on the main diagonal. When the input is a
matrix, it extracts the diagonal elements.

24. D
Both && and & represent logical AND in MATLAB. The && operator is
short-circuit AND (used for scalars), while & performs element-wise
AND and works on arrays.

25. B
The floor() function rounds toward negative infinity. For negative
numbers, this means rounding away from zero. floor(-3.7) rounds down
to -4.

26. D
Both the backslash operator (Ab) and linsolve(A, b) solve the linear
system Ax = b. The backslash operator uses optimized algorithms based
on matrix properties.

27. A
The reshape() function rearranges matrix elements into new dimensions.
Since 3×4 = 12 = 2×6, the reshape is valid. Elements are taken
column-wise from the original matrix.

28. B
The save() function saves workspace variables to a MAT-file. Using
save(‘filename’) saves all variables; specific variables can be
listed after the filename.

29. B
The strcmp() function performs case-sensitive string comparison.
MATLAB’ and ‘matlab’ differ in case, so the function returns 0
(false). Use strcmpi() for case-insensitive comparison.

30. B
When called with two output arguments, max(v) returns both the
maximum value and the index of its first occurrence. With one
output, it returns only the maximum value.

31. B
The “hold on” command retains the current plot so that subsequent
plotting commands add to the existing graph rather than replacing
it. Use “hold off” to return to default behavior.

32. B
The det() function computes the determinant of a square matrix.
The determinant is a scalar value that provides information about
the matrix properties, including invertibility.

33. C
The sum(A, dim) function sums along the specified dimension.
Dimension 2 represents columns, so sum(A, 2) computes the sum
of each row, returning a column vector.

34. C
The break keyword immediately exits the innermost FOR or WHILE
loop. Execution continues with the statement following the loop.
The continue keyword skips to the next iteration instead.

35. B
The find() function returns the linear indices of nonzero elements.
When combined with a logical expression like A > 5, it returns
the indices where the condition is true, not the actual values.

36. B
Cell arrays in MATLAB are created using curly braces {}. Cell arrays
can store data of different types and sizes in each cell, unlike
regular arrays which require uniform data types.

37. A
The rank() function computes the rank of a matrix, which is the
number of linearly independent rows or columns. It uses singular
value decomposition to determine the rank numerically.

38. B
The “who” command displays a list of all variables currently stored
in the MATLAB workspace. The “whos” command provides more detailed
information including size, bytes, and class.

39. B
The struct() function creates a structure array in MATLAB. Structures
allow you to group related data of different types using named fields,
similar to records in other programming languages.

40. B
The ceil() function rounds toward positive infinity. For negative
numbers, this means rounding toward zero. ceil(-2.3) rounds up
to -2, which is closer to positive infinity than -3.