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**LinkedIn MATLAB Assessment Answers**

**Question – From what distribution does the rand() function return value?**

- normal
- poisson
- binomial
**uniform**

**Question – 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

**Question – What does the Profiler track?**

**execution time**- command history
- errors
- the value of variables

**Question – Which code block contains the correct syntax for a while loop?**

- [ ] a = 0;

do a = a + 1;while a < 5end - [ ]

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**

**Question – 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

**Question – 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());

**Question – What is %% used for?**

- argument placeholder
- block quotes
**code sections**- conversion specifier

**Question – What is the . character NOT used for?**

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

**Question – Which function could you use for multiple linear regression?**

- polyval
**regress**- solve
- polyfit

**Question – 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]

**Question – 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.

**Question – How do you access the value for the field name in structure S?**

- S[‘name’]
**S.name**- S(‘name’)
- S{‘name’}

**Question – What built-in definition does i have?**

**basic imaginary unit**- index function
- infinity
- index variable

**Question – 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; **

**endend**

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

**Question – 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)

**Question – 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]

**Question – Which function CANNOT be used to randomly sample data?**

- datasample
- randi
**resample**- randperm

**Question – 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

**Question – 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

**Question – 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.

**Question – 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)

**Question – 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)

**Question – 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;

**Question – 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);enda = my_func(a);**

- 4
- 3
- 0
**1**

**Question – 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]}};

**Question – 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];

**Question – 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’;

**Question – 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])**

**Question – 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**

**Question – 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]);

**Question – 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’))**

**Question – 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

**Question – 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.

**Question – 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)

**Question – 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))

**Question – 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();

**Question – 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));**

**Question – 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)**

**Question – 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’)

**Question – Which is NOT a function that adds text to a plot?**

- title
- text
**label**- legend

**Question – Which code block most likely produced this graph?**

- [ ] figure

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

**[x] figure**

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

**Question – What kind of files are stored with the .mat extension?**

- figure files
- script files
- function files
**stored variable files**

**Question – 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));

**Question – Which statement returns 1 (true)? **

**a = ‘stand’b = “stand”**

** a == b**

ischar(b)

length(a) == length(b)

class(a) == class(b)

**Question – 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 =

**Question – Where in the UI can you see what variables have been created, their values, and their class?**

- Editor
- command window
- details
**workspace**

**Question – 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 3.2586y = 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 onplot(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 onplot(x_line,y_line)

**Question – 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.

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