MATLAB Assessment Questions and Answers

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 MATLAB Assessment Questions and Answers



1. 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)

 


2. 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)

 


3. 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;

 


4. 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 



5. 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]}};


 

6. Which code block most likely produced this graph?

 

How to pass LinkedIn MATLAB Assessment Test

 

figure

x = rand(10,10);

r = corrcoef(x);

surf(r)

colorbar

 

figure

x = rand(10,10);

r = corrcoef(x);

imagesc(r)

colorbar

 

 

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

 

figure files

script files

function files

stored variable files

 

 

8. 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));

 

9. Which statement returns 1 (true)?

 

a = 'stand'

b = "stand"

 

a == b

ischar(b)

length(a) == length(b)

class(a) == class(b)

 

 

10. 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'}



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

 

Editor

command window

details

workspace

 

12. 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)

 

 

13. 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.

 

 

14. 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());

 


15. What is %% used for?

 

argument placeholder

block quotes

code sections

conversion specifier



 

16. what is the . character NOT used for?

 

structure field access

a decimal point

cell array access

element-wise operations

 

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

 

polyval

regress

solve

polyfit

 

18. 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]

 

19. 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.

 

 

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

 

S['name']

S.name

S('name')

S{'name'}



21. What built-in definition does i have?

 

basic imaginary unit

index function

infinity

index variable

 


22. 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

end

 

b = a*a;

b = a.^2;

b = a^2;

b = pow2(a);

 

 

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

 

normal

poisson

binomial

uniform

 


24. 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

 


25. What does the Profiler track?

 

execution time

command history

errors

the value of variables



26. 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];

 

 

27. 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';

 

 

28. 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)


 

 

29. 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)


 

30. 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]);

 

 

 

31. 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'))

 

 

32. 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

 


33. 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.

 

 

 

34. 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)

 

 

 

35. 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))

 


36. 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();

 

  

 

37. 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)

 


38. 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')

 

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

 

  •  title

  •  text

  •  label

  •  legend

 


40. 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)

 


41. 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]

 


42. Which function CANNOT be used to randomly sample data?

 

  •  datasample

  •  randi

  •  resample

  •  randperm

 


43. Which choice is correct syntax for a switch statement?

 

  • [x] x = 7;

switch x

    case 2

        disp("two");

    otherwise

        disp("not two");

end

 

  • [ ] x = 7;

switch x :

    case 2

        disp("two");

    otherwise

        disp("not two");

end

 

  • [ ] x = 7;

switch x

    case 2

        disp("two");

    else

        disp("not two");

end

 

  • [ ] x = 7;

switch x

    case 2

        disp("two");

    default

        disp("not two");

end

 

 

44. What is the result of this code?

 

a = 1;

b = 2;

c = 3;

d = 4;

e = c / (~a - b == c - d);

 

  •  c =    NaN

  • Error

  •  c =    Inf

  • c =     -0.2500

 


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
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