linkedin-skill-assessments-quizzes

MATLAB

Q1. From what distribution does the rand() function return value?

Q2. Based on the code below, c is the _ of a.

a = rand(1, 11);
b = sort(a);
c = b(1, ceil(end/2));

Q3. What does the Profiler track?

Reference

Q4. Which code block contains the correct syntax for a while loop?

a = 0;
do
    a = a + 1;
while a < 5
end

a = 0;
while(a < 5)
    a = a + 1;

a = 0;
while a < 5:
    a = a + 1;

a = 0;
while a < 5
    a = a + 1;
end

Q5. What does b contain?

a =
    19    20    12     0     6
     6     9    56     0     3
    46     8     9     8    19
     9     8     8    19    46
     1     9    46     6    19

b =

    56     0
     9     8

b =

     8    19
    19    46

Q6. 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());

Q7. What is %% used for?

Q8. what is the . character NOT used for?

Q9. Which function could you use for multiple linear regression?

Q10. For which of these arrays do mean, median, and mode return the same value?

Q11. 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)

Q12. How do you access the value for the field name in structure S?

Q13. What built-in definition does i have?

Q14. 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

Q15. 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?

Q16. What is the value of c?

a = ones(1,3);
b = 1:3;
c = conv(a,b)

Q17. Which function CANNOT be used to randomly sample data?

Q18. Which choice is correct syntax for a switch statement?

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

Q19. What is the result of this code?

a = 1;
b = 2;
c = 3;
d = 4;
e = c / (~a - b == c - d);

c =
    NaN

c =
    Inf

c =
    -0.2500

Q20. What is true of a handle class object?

Q21. Which choice has a different final result in f10 than the other three?

f10 = 1;
for i = 1:10
    f10 = f10 * i;
end

f10 = 1;
i = 1;
while i <= 10
    i   = i + 1;
    f10 = i * f10;
end

Q22. Which choice will NOT give you a 5 x 5 identity matrix?

a = rand(5);
round(a * inv(a))

Q23. Which statement creates this structure?

dog =

      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;

Q24. my_func is a function as follows. What is the value of a 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);

Q25. Which statement could create this cell array?

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

Q26. Which choice adds b to each row of a?

a = ones(4, 4);
b= [1 2 3 4];

Q27. 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';

Q28. Which statement returns the roots for the polynomial x^2 + 2x - 4?

Q29. Which choice is the proper syntax to append a new elements a to the end of 1x 2 dimensional cell array C?

Q30. 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?

Q31. Which statement returns a cell array of the strings containing ‘burger’ from menu?

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

Q32. What is the set of possible values that a may contain?

a      = randi(10, [1, 10]);
a(3)   = 11;
a(a>2) = 12;

Q33. Which statement is true about the sparse matrices?

Q34. Which statement using logical indices will result in an error?

a = 1:10;

Q35. 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'

Q36. Which code snippet sets a new random seed based on the current time and saves the current settings of the random number generator?

rng(time());
rng_settings_curr = rng();

rng('shuffle');
rng_settings_curr = rng();

Q37. You have a matrix data in which each column is mono audio recording from a room in your house. You’ve noticed that each column has a very different mean and when you plot them all on the same graph, the spread across the y axis make it impossible to see anything. You want to subtract the mean from each column. Which code block will accomplish this?

data_nomean = zeros(size(data));
for i = 1:size(data, 1)
    data_nomean(i, :) = data(i, :) - mean(data(i, :));
end

Q38. 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 = zeros(1, size(C, 1));
for i_C = 1:size(C, 1)
    b(i_C) = mean(C{i_C}(:));
end

Q39. 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'};

Q40. Which is NOT a function that adds text to a plot?

Q41. Which code block most likely produced this graph?

MatLab Q39

figure
x = rand(10,10);
r = corrcoef(x);
surf(r)
colorbar

figure
x = rand(10,10);
r = corrcoef(x);
imagesc(r)
colorbar

Q42. What kind of files are stored with the .mat extension?

Q43. 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;

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));

Q44. Which statement returns 1 (true)?

a = 'stand'
b = "stand"

Q45. Which does E contain?

C = {'dog' 'cat' 'mouse'}
D = {'cow' 'piranha' 'mouse'}
E = setdiff(C,D)

Q46. Where in the UI can you see what variables have been created, their values, and their class?

Q47. 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)

Q48. 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;

Q49. Which command will create a 10-element vector v with values from 1 to 10?

Q50. For a 5 x 5 array, the two subscript index (4,2) indexes the same location as linear index ___.

Q51. What is a difference between global variable and persistent variables?

Q52. How is the random seed for MATLAB’s random number generator first initializedin a MATLAB Session?

Reference

Q53. At what will MATLAB look first for a called function?

Reference

Q54. 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

Reference

Q55. 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

Reference

Q56. 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?

Q57. Which statement will return all the odd numbers from 1 to 9?

Q58. 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));

Q59. What is the size of b?

a = [1 2 3];
b = repmat(a,2,3);

Q60. Which statement reverses vector a?

a = [ 1 2 3 4];

Q61. Which command will create a column vector with the values 7, 8, and 9?

Q62. What do you call in the command window to see all the variables in the workspace and their classes?

Q63. 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?

Q64. What is a reason to save a MAT-file using the -v7.3 flag?

Q65. Which choice cannot add a directory to the search path?

Reference

Q66. Which is not a function to plot three-dimensional data?

Reference

Q67. What is the reason to save a MAT-file using the v-7.3 flag?

Reference

Q68. This graph could be the result of which block of code?

MatLab Q41

Q69. What is a key difference between && and &?

Reference

Q70. What is the result of this code?

s="abcd"; s(3)='x'

Q71. In which case would you use varargin in a function you write?

Q72. What does e contain?

c = [9 8 0];
d = [0 0 1];
e = union(c,d);

Q73. What does this function print?

a = 1;
for i_loop = 1:6
    disp(a);
end

111111

1 1 1 1 1 1

1
1
1
1
1
1

nothing will print

Q74. You are debugging a function and have set a breaipoint on the line before the error occurs. You look at the variable values and suspect the cause of the error is that a is 9 but should be 10. The next statement after the breakpoint will use a. Wigh action would help you test if a=10 solves the problem?

Q75. Which statement returns the character array ‘alone’?

b = ['stand' 'alone'];

Q76. Which statement returns the character array ‘alone’?

c = {rand(20,10) rand(23,2) rand(14,5)}

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

b = zeros(1, size(C,1);
    for i_C = 1:size(C,1)
        b(1_C) = mean(C{i_C}(:));
    end

b = cellfun(@mean, C)

b = zeros(1, size(C,2);
    for i_C = 1:size(C,2)
        b(1_C) = mean(C(i_C));
    end

Q77. Which choice uses the proper syntax for an if else statement?

if (a > 1):
    b = 2;
else:
    b = 3;

if (a > 1){
    b = 2;
} else{
    b = 3;
}

if (a > 1)
    b = 2;
else
    b = 3;
end

if (a > 1)
    b = 2;
else
    b = 3;

Reference

Q78. What does b contain?

a = [9 8 8 19 6 1 9 6 6 19];
b = unique(a);
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