MATLAB Assessment

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?

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 = factorial(10)

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

f10 = prod(1:10)

Q22. 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)

Q23. 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;

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_settings_curr = rng('shuffle');

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

rng_settings_curr = rand('shuffle');

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 = data - repmat(median(data), size(data, 1), 1);

data_nomean = bsxfun(@minus, data, mean(data));

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

data_nomean = zscore(data');

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 = 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)

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;

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));

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)