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MATLAB

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

  • normal
  • poisson
  • binomial
  • uniform

Q2. 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

Q3. What does the Profiler track?

  • execution time
  • command history
  • errors
  • the value of variables

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;
  • [x]
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
  • [x]
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());
  • [x]
tic;
myfun();
toc;
  • [ ]
timer.start;
myfun()
t = timer.stop;
  • [ ]
t = timer(myfun());

Q7. What is %% used for?

  • argument placeholder
  • block quotes
  • code sections
  • conversion specifier

Q8. what is the . character NOT used for?

  • structure field access
  • a decimal point
  • cell array access
  • element-wise operations

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

  • polyval
  • regress
  • solve
  • polyfit

Q10. 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]

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)
  • 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.

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

  • S['name']
  • S.name
  • S('name')
  • S{'name'}

Q13. What built-in definition does i have?

  • basic imaginary unit
  • index function
  • infinity
  • index variable

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
  • b = a*a;
  • b = a.^2;
  • b = a^2;
  • b = pow2(a);

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?

  • xticks(-3pi:3.14:3pi)
  • xticks(-3pi:pi:3pi)
  • xticks(linespace(-3pi(), 3pi(), pi()))
  • xticks(linespace(-3pi, 3pi, pi)

Q16. 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]

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

  • datasample
  • randi
  • resample
  • randperm

Q18. 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

Q19. What is the result of this code?

a = 1;
b = 2;
c = 3;
d = 4;
e = c / (~a - b == c - d);
  • Error
  • [ ]
c =
    NaN
  • [x]
c =
    Inf
  • [ ]
c =
    -0.2500

Q20. 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 function.

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)
  • [x]
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);
  • [x]
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);
  • 4
  • 3
  • 0
  • 1

Q25. 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]}};

Q26. 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];

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
  • [x]
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?

  • poly([1 2 -4])
  • solve(x^2 + 2x - 4 == 0)
  • polyfit(x^2 + 2x - 4 == 0)
  • roots([1 2 -4])

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

  • C = {C a};
  • C = cellcat(C a)
  • C = cat(2, {a}, C)
  • C{end+1}=a

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?

  • 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]);

Q31. 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'))

Q32. 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

Q33. 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.

Q34. 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)

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'
  • menu_string = cell2mat(join(menu, newline))
  • menu_string = cell2mat(join(menu, '\n'))
  • menu_string = join(menu, newline)
  • menu_string = cell2mat(pad(menu))

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'};

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

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

  • title
  • text
  • label
  • legend

Q41. Which code block most likely produced this graph?

MatLab Q39

  • [ ]
figure
x = rand(10,10);
r = corrcoef(x);
surf(r)
colorbar
  • [x]
figure
x = rand(10,10);
r = corrcoef(x);
imagesc(r)
colorbar

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

  • figure files
  • script files
  • function files
  • stored variable files

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"
  • a == b
  • ischar(b)
  • length(a) == length(b)
  • class(a) == class(b)

Q45. 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'}
  • E =

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

  • Editor
  • command window
  • details
  • workspace

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
  • [x]
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;
  • 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.

Q49. 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)

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

  • 7
  • 8
  • 17
  • 9

Q51.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.

Q52. How is the random seed for MATLAB's random number generator first initializedin 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.

Reference

Q53. 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

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
  • [x]
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
  • [x]
a =
    5
    7
  • [ ]
a =
    6
    7
  • [ ]

Reference