MATLAB Linkedin Assessment Question Answers

March 18, 2022

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LinkedIn MATLAB Assessment Questions and Answers

Whats on the linkedin matlab quiz

1. What is a difference between global variable and persistent variables?

Global variables have a higher performance overhead than persistent variables.

Global variables remain in memory after clear all; persistent variables do not.

Global variables can be used to cache data in memory; persistent variables cannot.

Global variables are accessible outside the function scope; persistent variables are not.

2. How is the random seed for MATLAB's random number generator first initialized in a MATLAB Session?

Seed is undefined until it is initialized by the user.

Seed is set to a value based on the current time when user first calls rand()

Seed is set to a value based on the current time on startup.

Seed is set to a static default value on startup.

3. At what will MATLAB look first for a called function?

functions on the path

built-in functions

functions within the current file

functions within the current directory

4. Which choice is the correct syntax for declaring a function that returns the input value as the output?

function mystery_func(a) :

return a

function b = mystery_func(a)

b = a;

end

def b = mystery_func(a)

b = a;

end

function mystery_func(a)

b = a;

return b;

end

5. What is the state of a, at the end of this code?

a = [1 2; 3 4];

b = a(:,2);

c = b + 3;

a(1:2,1) = c;

a =

6 3

7 4

a =

5 2

7 4

a =

5

7

a =

6

7

6. Which choice has a different final result in f10 than the other three?

f10 = 1;

for i = 1:10

f10 = f10 * i;

end

f10 = factorial(10)

f10 = 1;

i = 1;

while i <= 10

i = i + 1;

f10 = i * f10;

end

f10 = prod(1:10)

7. Which choice will NOT give you a 5 x 5 identity matrix?

a = rand(5);

round(a * inv(a))

diag(ones(5, 1))

identity(5)

eye(5)

8. Which statement creates this structure?

dog =

name: 'Bindy'

breed: 'border collie'

weight: 32

dog = struct('name', 'Bindy'; 'breed', 'border collie'; 'weight', 32);

dog.name = 'Bindy';

dog.breed = 'border collie';

dog.weight = 32;

dog = {

'name' : 'Bindy',

'breed' : 'border collie',

'weight': 32;

}

dog('name') = 'Bindy';

dog('breed') = 'border collie';

dog('weight') = 32;

9. my_func is a function as follows. What is the value of an at the end of the code beneath?

function a = my_func(a)

a = a + 1;

end

------------------

a = 0;

for i = 1:3

my_func(a);

end

a = my_func(a);

1

4

3

0

10. Which statement could create this cell array?

c = {["hello world"]} {1×1 cell} {["goodbye"]} {1×3 double}

c = {"hello world" {"hello"} "goodbye" [1 2 ]};

c = {"hello world" {"hello"} "goodbye" {[1 2 3]}};

c = {"hello world" {"hello"} "goodbye" [1 2 3]};

c = {"hello world" {"hello" "hello"} "goodbye" {[1 2 3]}};

11. Which code block most likely produced this graph?

figure

x = rand(10,10);

r = corrcoef(x);

surf(r)

colorbar

figure

x = rand(10,10);

r = corrcoef(x);

imagesc(r)

colorbar

12. What kind of files are stored with the .mat extension?

figure files

script files

function files

stored variable files

13. You would like to randomly reorder every element in array a and put the result into another array b. Which code is NOT necessary to do that?

a = 1:10;

b = a(randi(10, 1, 10));

m = perms(a);

i = randi(factorial(10), 1);

b = a(m(i, :))

[s, j] = sort(rand(10, 1));

b = a(i);

b = a(randperm(10));

14. Which statement returns 1 (true)?

a = 'stand'

b = "stand"

a == b

ischar(b)

length(a) == length(b)

class(a) == class(b)

15. Which does E contain?

C = {'dog' 'cat' 'mouse'}

D = {'cow' 'piranha' 'mouse'}

E = setdiff(C,D)

E = {'cat'} {'dog'}

E = {'mouse'}

E = {'cat'} {'cow'} {'dog'} {'piranha'}

16. Where in the UI can you see what variables have been created, their values, and their class?

Editor

command window

details

workspace

17. Given the following x and y coordinates, which choice calculates a linear regression for the x and y coordinates, and which plots the points of the x,y data and the regression line on the same graph?

x = 9.0646 6.4362 7.8266 8.3945 5.6135 4.8186 2.8862 10.9311 1.1908 3.2586

y = 15.4357 11.0923 14.1417 14.9506 8.7687 8.0416 5.1662 20.5005 1.0978

coeff_line = polyfit(x,y,1)

x_line = floor(min(x)):0.1:ceil(max(x));

y_line = polyval(coeff_line,x_line)

figure; plot(x,y,'o')

hold on

plot(x_linemy_line)

figure

plot(x,y,'o')

coeff_line = polyfit(x,y,1);

x_line = floor(min(x)):0.1:ceil(max(x));

y_line = polyval(coeff_line,x_line);

plot(x_line,y_line)

figure

plot(x,y)

coeff_line = polyfit(x,y,1);

x_line = floor(min(x)):0.1:ceil(max(x));

y_line = polyval(coeff_line,x_line);

hold on; plot(x_line,y_line)

coeff_line = polyfit(x,y,1);

x_line = floor(min(x)):0.1:ceil(max(x));

y_line = polyval(coeff_line,x_line);

figure; plot(x,y,'o')

hold on

plot(x_line,y_line)

18. If you run this piece of code, you will get an error. Why?

a = [0 1 2 3; 4 5 6 7];

a = a^2;

You are attempting to multiply a non-square matrix by itself, causing a dimension mismatch.

MATLAB does not allow you to square all the elements in the matrix in a single operation.

You must use the ** operator instead of the ^ operator.

You cannot square matrices that have a 0 as the first element.

19. You have written a function myfun and want to measure how long it takes to run. Which code segment will return in t the time in seconds it takes myfun to run?

t = cputime(myfun());

tic;

myfun();

toc;

timer.start;

myfun()

t = timer.stop;

t = timer(myfun());

20. What is %% used for?

argument placeholder

block quotes

code sections

conversion specifier

21. what is the . character NOT used for?

structure field access

a decimal point

cell array access

element-wise operations

22. Which function could you use for multiple linear regression?

polyval

regress

solve

polyfit

23. For which of these arrays do mean, median, and mode return the same value?

[0 1 1 1 2]

[1 3 5 5 6]

[0 1 1 1 1]

[0 0 5 5 5]

24. You are in the middle of a long MATLAB session where you have performed many analyses and made many plots. You run the following commands, yet a figure window doesn't pop up on the top of your screen with your plot. What might be the issue?

x = [-1:0.1:1];

y = X.^2;

plot(x, y)

Your plot doesn't plot in a figure window because figure was not called immediately in advance.

Your plot syntax is incorrect.

Your plot is in a figure window that was already open, hidden behind other windows on your screen.

Your plot was saved to an image file but not displayed.

25. How do you access the value for the field name in structure S?

S['name']

S.name

S('name')

S{'name'}

26. What built-in definition does i have?

basic imaginary unit

index function

infinity

index variable

27. Which statement is equivalent to this for loop?

a = [1 2 3; 4 5 6];

b = zeros(size(a));

for i_row = 1:size(a, 1)

for i_col = 1:size(a, 2)

b(i_row, i_col) = a(i_row, i_col)^2;

end

b = a*a;

b = a.^2;

b = a^2;

b = pow2(a);

28. From what distribution does the rand() function return value?

normal

poisson

binomial

uniform

29. Based on the code below, c is the \_ of a.

a = rand(1, 11);

b = sort(a);

c = b(1, ceil(end/2));

median

mode

mean

margin

30. What does the Profiler track?

execution time

command history

errors

the value of variables

31. Where in the UI can you see what variables have been created, their values, and their class?

Editor

command window

details

workspace

32. Given the following x and y coordinates, which choice calculates a linear regression for the x and y coordinates, and which plots the points of the x,y data and the regression line on the same graph?

x = 9.0646 6.4362 7.8266 8.3945 5.6135 4.8186 2.8862 10.9311 1.1908 3.2586

y = 15.4357 11.0923 14.1417 14.9506 8.7687 8.0416 5.1662 20.5005 1.0978

coeff_line = polyfit(x,y,1)

x_line = floor(min(x)):0.1:ceil(max(x));

y_line = polyval(coeff_line,x_line)

figure; plot(x,y,'o')

hold on

plot(x_linemy_line)

[ ]

figure

plot(x,y,'o')

coeff_line = polyfit(x,y,1);

x_line = floor(min(x)):0.1:ceil(max(x));

y_line = polyval(coeff_line,x_line);

plot(x_line,y_line)

[ ]

figure

plot(x,y)

coeff_line = polyfit(x,y,1);

x_line = floor(min(x)):0.1:ceil(max(x));

y_line = polyval(coeff_line,x_line);

hold on; plot(x_line,y_line)

[ ]

coeff_line = polyfit(x,y,1);

x_line = floor(min(x)):0.1:ceil(max(x));

y_line = polyval(coeff_line,x_line);

figure; plot(x,y,'o')

hold on

plot(x_line,y_line)

33. If you run this piece of code, you will get an error. Why?

a = [0 1 2 3; 4 5 6 7];

a = a^2;

You are attempting to multiply a non-square matrix by itself, causing a dimension mismatch.

MATLAB does not allow you to square all the elements in the matrix in a single operation.

You must use the ** operator instead of the ^ operator.

You cannot square matrices that have a 0 as the first element.

34. Which command will create a 10-element vector v with values from 1 to 10?

v = {1:10}

v = [1-10]

v = 1:10

v = (10)

35. For a 5 x 5 array, the two subscript index (4,2) indexes the same location as linear index ___.

7

8

17

9

36. You've just plotted some data and want to change the color behind the lines you've plotted to black. Which code block will accomplish this?

h_f = figure; set(h_f,'Color', [0 0 0]);

h_a = gca; set(h_a,'Color', [0 0 0]);

h_a = axes; set(h_a,'Color', [0 0 0]);

h_f = gcf; set(h_a,'Color', [0 0 0]);

37. Which statement will return all the odd numbers from 1 to 9?

2*[1:5]+1

1:2:9

isodd(1:9)

1:odd:9

38. In MATLAB, the imfilter command performs a convolution operation between an image and a matrix. Suppose you have an image loaded in MATLAB into the variable img and you apply the following code. The original image appears slightly blurred because the convolution smoothed out the image (removed noise). Why do you think this happened?

h = ones(5,5)/25;

imshow(imfilter(img,h));

h is a Gaussian filter that adds to 1. Its intended effect is to highlight image edges.

h is an averaging filter uniformly distributed that adds to 1. Its intended effect is to smooth out images (remove noise).

h is a Laplacian filter that adds up to 0. Its intended effect is to smooth out images (remove noise).

imfilter is a function that always blurs the images.

39. What is the size of b?

a = [1 2 3];

b = repmat(a,2,3);

1x3

3x2

2x3

2x9

40. Which statement reverses vector a?

a = [ 1 2 3 4];

reverse(a)

a(end:- 1:1)

rev(a)

a(::-1)

41. Which command will create a column vector with the values 7, 8, and 9?

c = [7,8,9]

c = [7: 8: 9]

c = [7; 8; 9]

c = [7 8 9]

42. What do you call in the command window to see all the variables in the workspace and their classes?

who

vars

whos

who all

43. You wrote a new function named snap in an m-file and when you call it, you're not getting the output you expect. You previously wrote a different function named snap, which you think might also be on the search path. Which command can you use to see if the old snap function is being called?

which

who

lookfor

what

44. What is a reason to save a MAT-file using the -v7.3 flag?

to ensure backward compatibility

to avoid HDF5 overhead in MAT-file

to include a variable greater that 2GB

to use compression by default

45. What is true of a handle class object?

When you pass a handle object to a function, a new object is made that is independent of the original.

All copies of handle objects refer to the same underlying object.

Handle object cannot reference one another.

Handle object do not have a default eq func

46. Which choice adds b to each row of a?

a = ones(4, 4);

b= [1 2 3 4];

a = a + reshape(b, 4, 1);

a = a + b';

a = a + repmat(b, 4, 1);

a = a + [b b b b];

47. Which choice replaces all as with os?

for i = 1:length(fruit)

fruit{i}(fruit{i} == a) == o;

end

for i = 1:length(fruit)

fruit(i)(fruit(i) == 'a') == 'o';

end

for i = 1:length(fruit)

fruit{i}(fruit{i} == 'a') == 'o';

end

for i = 1:length(fruit)

fruit{i}(fruit{i} == 'a') == 'o';

48. Which statement returns the roots for the polynomial x^2 + 2x - 4?

roots([1 2 -4])

poly([1 2 -4])

solve(x^2 + 2x - 4 == 0)

polyfit(x^2 + 2x - 4 == 0)

49. Which choice is the proper syntax to append a new elements a to the end of 1x 2 dimensional cell array C?

C{end+1}=a

C = {C a};

C = cellcat(C a)

C = cat(2, {a}, C)

50. You have loaded a dataset of people's heights into a 100 x 1 array called height. Which statement will return a 100 x 1 array, sim_height, with values from a normal distribution with the same mean and variance as your height data?

sim_height = std(height) + mean(height) * randn(100, 1);

sim_height = mean(height) + std(height) * randn(100, 1);

sim_height = randn(std(height), mean(height), [100, 1]);

sim_height = randn(mean(height), std(height), [100, 1]);

51. Which statement returns a cell array of the strings containing 'burger' from menu?

menu = {'hot dog' 'corn dog' 'regular burger' 'cheeseburger' 'veggie burger'}

menu{strfind(menu, 'burger')}

menu(strfind(menu, 'burger'))

menu{contains(menu, 'burger')}

menu(contains(menu, 'burger'))

52. What is the set of possible values that a may contain?

a = randi(10, [1, 10]);

a(3) = 11;

a(a>2) = 12;

3, 4, 5, 6, 7, 8, 9, 10, 11, 12

1, 2, 12

2, 11, 12

1, 12

53. Which statement is true about the sparse matrices?

You can use the sparse function to remove empty cells from cell array variables.

Sparse matrices always use less memory than their associated full matrices.

Mixtures of sparse and full matrices can be combined in all of MATLAB's built-in arithmetic operations.

The sparse function requires its input to be a full matrix with at least 50% zero elements.

54. Which statement using logical indices will result in an error?

a = 1:10;

b = a(a ~= 11)

b = a(a == 1)

b = a(a>6 && a<9)

b = a(a | 1)

55. Which statement turns menu into the variable menu_string below?

menu = {'hot dog' 'corn dog' 'regular burger' 'cheeseburger' 'veggie burger'}

menu_string =

'hot dog

corn dog

regular burger

cheeseburger

veggie burger'

menu_string = cell2mat(join(menu, newline))

menu_string = cell2mat(join(menu, '\n'))

menu_string = join(menu, newline)

menu_string = cell2mat(pad(menu))

56. Which code snippet sets a new random seed based on the current time and saves the current settings of the random number generator?

rng_settings_curr = rng('shuffle');

rng(time());

rng_settings_curr = rng();

rng_settings_curr = rand('shuffle');

rng('shuffle');

rng_settings_curr = rng();

57. Which code block results in an array b containing the mean values of each array within C?

b = zeros(1, size(C, 2));

for i_C = 1:size(C, 2)

b(i_C) = mean(C(i_C));

end

b = cellfun(@mean, C);

b = zeros(1, size(C, 1));

for i_C = 1:size(C, 1)

b(i_C) = mean(C{i_C}(:));

end

b = cellfun(@(m) mean(m(:)), C)

58. Which statement creates a logical array that is 1 if the element in passwords contains a digit and 0 if it does not?

passwords = {'abcd' '1234' 'qwerty' 'love1'};

contains(password, '\d')

~isempty(regexp(passwords, '\d'))

cellfun(@(x) ~isempty(regexp(x, '\d')), passwords)

regexp(passwords, '\d')

59. Which is NOT a function that adds text to a plot?

title

text

label

legend

60. You have plotted values of cosine from -10 to 10 and want to change the x-axis tick marks to every pi, from -3pi to 3pi. Which statement will do that?

xticks(-3pi:3.14:3pi)

xticks(-3pi:pi:3pi)

xticks(linespace(-3pi(), 3pi(), pi()))

xticks(linespace(-3pi, 3pi, pi)

61. What is the value of c?

a = ones(1,3);

b = 1:3;

c = conv(a,b)

[-1 2 -1]

[1 3 6 5 3]

6

[1 -2 1]