Department of Computer Science
Computer Science 101: Mid Term Exam I (60 minutes)
Name: NetID:
Lab Section: Date:
No questions
will be answered during this examination.
If you do not understand a question, read it again. If you still do not understand it, make reasonable assumptions and write them
down. (Points will be deducted if unreasonable assumptions are made.)
DO NOT CHEAT: Cheating includes not only copying from another person but
also allowing someone to copy from you.
Anyone who copies or allows someone to copy will receive a score of
zero. So be defensive and protect your
work.
This examination contains 10 pages including this page. Check that your copy is complete, and ask for a replacement if it is not. Do all your work on these pages. For your own protection, in case pages come apart, write your NetID at the TOP of each page before beginning work.
Do not forget to sign the attendance list. If your exam is
misplaced and you did not sign the attendance list then you will receive a zero
score for the exam.
You may not use any electronic devices, book, notes or other
references during this examination.
DO NOT WRITE IN THIS SPACE
Section |
Possible Score |
Deduction |
Grader |
|
5 |
|
|
|
|
2 |
6 |
|
|
|
3 |
6 |
|
|
|
4 |
8 |
|
|
|
5 |
8 |
|
|
|
6 |
6 |
|
|
|
7 |
10 |
|
|
|
8 |
6 |
|
|
|
9 |
8 |
|
|
|
10 |
5 |
|
|
|
11 |
6 |
|
|
|
12 |
6 |
|
|
|
13 |
6 |
|
|
|
14 |
8 |
|
|
|
15 |
5 |
|
|
|
16 |
6 |
|
|
|
17 |
5 |
|
|
|
18 |
5 |
|
|
|
19 |
10 |
|
|
|
Total |
125 |
|
|
|
|
|
Exam Scoreŕ |
|
A
1. Circle the correct output the following command produces when typed at the Matlab prompt:
>> linspace(2,5,4)
a) 2 2.5 3 3.5
4
b) 2 3 4 5
c) 2
d) 5 4 3 2
2. Given that the variable x contains a row vector of numbers, write a single Matlab statement that would square each number in x and store the result in a variable y?
________________________________________________________________
3.
Write the results
Matlab returns for the sequence of commands typed in the Matlab command window:
>>clear;
>>cat = [1 3 5 7 11];
>>cat + 3;
>>who
_________________________________________________________________________
4. Given that dog = [2 4 6 10 14], which Matlab expression below would give you the vector
[4 10]? Please circle each correct answer.
a) dog(2:2:5)
b) dog(2:4)
c) dog(4:2:10)
d) dog(4:-2:2)
5.
Write a Matlab
expression to display a single random integer (not real) in the range from 0
to 5,including 0 and 5. You must use the rand and floor functions.
_________________________________________________________________________
6. Write a single Matlab command to compute the second derivative of x4. (You must use the diff function. Assume x has been previously declared as a symbol, with the syms x command).
_________________________________________________________________________
7. Write the results Matlab returns for the sequence of commands typed in the Matlab command window:
a)
>> x = sum([2 4 6])
x =
_________________________________________________________________________
b)
>>
x = floor([ 1.7 3.6
.8 ] )
x =
_________________________________________________________________________
c)
>> x = min([6 4 2; 2 4 6])
x =
_________________________________________________________________________
d)
>> x = roots([1 0 -4])
x =
_________________________________________________________________________
e)
>> x = cumsum([2 4 6 8])
x =
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8. A Matlab programmer downloaded a Matlab file named avg.m from Internet, which contains a function named avg. But for some reason, the definition line (first line) of this function is missing. Read the program and comments and then write out the missing function definition line.
%input: a non-empty
vector, x
%output: the average
value of the vector
n = length(x);
avg = sum(x)/n;
_________________________________________________________________________
9. Assume the function named func is defined below and saved in the file func.m :
function
z = func(x, y)
global
g
g
= [g, x, y];
z
= x+y;
At the Matlab prompt you type the following commands. Fill in the blanks with the correct values that Matlab would return.
>> clear
>> global g
>>
g = [];
>> z = func(1, 2);
>> x = func(z, 3);
>> who
_________________________________________________________________________
>> g
g =
_________________________________________________________________________
>> x
x =
_________________________________________________________________________
10. Let
A be a 2 x 3
matrix and B be a 3 x 4
matrix that contain numerical values. Which of the following are valid
operations, that is, which of the following will not produce Matlab errors? Circle each valid operation. There may
be more than one valid operation.
B * A
A * B
A * A
B * [A, A]
B * [A ; A]
11. Assume that file fnc.m has the following content:
function b =
fnc(a)
b=2;
scr;
b = [b, a, c,
0];
and that the file scr.m has the following content:
c = 2;
c = [a, c];
Write the results Matlab returns for the sequence of commands typed in the Matlab command window:
>> clear
>> a =
1;
>> b =
2;
>> c =
3;
>> d =
fnc(c);
>> d
d =
_________________________________________________________________________
12. Fill
in the six blanks to create the following matrix named bigmat.
>> bigmat = [eye(____),zeros(____
, ____);3*ones(____),zeros(____ , ____)]
bigmat =
1 0 0
0 0
0 1 0
0 0
3 3 3
0 0
3 3 3
0 0
3 3 3
0 0
13. Given
that the file named fancy.m contains the following code:
function y = fancy(x)
y = x - 4;
Fill in the blank below with the correct Matlab response.
>> y = fancy( fzero(@fancy, 1) )
y =
_____________________________________________________________________
14. Assume
that the following Matlab commands have been typed at the Matlab command
prompt:
>> x = linspace(-pi, pi, 100);
>> y = sin(x);
Which of the following Matlab commands will plot the
function y = sin(x) where x takes values from the interval [-pi , pi]. Circle each correct answer. There
may be more than one correct answer.
a)
>> plot(x,y)
b)
>> plot(y,x)
c)
>> plot( x , sin(x))
d)
>> plot(sin(x))
15. Would
the following Matlab commands produce an error?
>> x =
[-3,-2,-1,0,1,2,3];
>> y =
[-2,-1,0,1,2];
>> [X,Y]
= meshgrid(x,y);
>>
surf(X,Y,cos(X.^3-Y.^3))
(Circle one) YES
NO
16. What is
the result Matlab returns for the following sequence of commands typed in the
Matlab command window? Circle the correct answer. (Note: there is only one correct answer.)
>> x = [2 3 5 7 4];
>> y = [4 9 13 49 16];
>> z = max(y(x.^2 == y))
z =
a) 4 9 25 49 16
b) 4
c) 49
d) 16
17. Assume
that the file myscript.m has
the following contents:
temp = y;
y = x;
x = temp;
What is the value of the three-element
row vector z after the following sequence of
commands has been typed in the Matlab command window? Circle the correct
answer. (Note: there is only one correct answer.)
>> x = 5;
>> y = 3;
>> myscript
>> myscript
>> z = [x y temp]
a) 5 3 5
b) Undefined
function or variable ‘temp’.
c) 3 5 3
d) 3 5 5
e) 5 3 3
18. Which
of the following Matlab commands is a correct way of computing an approximation
of the definite integral of the function f(x) = cos(x)
+ sin(x) on the real interval [0,5]? Circle
each of the correct answers. (Note: there may be more that one correct answer.)
a) >>
quadl('sin + cos',[0,5])
b) >>
quadl('sin(x) + cos(x)',0,5)
c) >> quadl(@(x)
sin(x) + cos(x),0,5)
d) >>
trapz('sin(x) + cos(x)',0,5)
e) >> trapz(@(x)
sin(x) + cos(x),0,5)
19. Write a complete Matlab function named f_to_c that converts Fahrenheit temperature into Celsius temperature. The function f_to_c has one input parameter fahr (a value in degree Fahrenheit), and the function returns the equivalent value in degree Celsius. Do not include comments in your function.
Use the following
conversion formula:
celsius = (fahr - 32) * 9/5