1. Electrical and Computer Engineering Department SUNY – New Paltz
Computer Simulation
“Lecture 9”
Electrical and Computer Engineering Department
SUNY – New Paltz
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2. Plots a bar-graph of a vector
bar(v)
Plots a bar-graph of a vector
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3. Exercise
Use bar() function to display a vector of prime numbers (1 thru 43). Hint: use primes() function.
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4. Exercise
In the previous exercise, use a for loop that will print the value of each bar on the top it.
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5. Exercise
Toss a coin N times (user selectable). Store the number of tails in x(1) and the number of heads in x(2). Then use bar(x) to compare them together.
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6. Exercise
Roll a die N times (user selectable). Store the number of ones in x(1) and the number of two’s in x(2) and so on. Then use bar(x) to compare them together.
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7. Frequencies, bar charts and histograms
A random walk
Imagine an ant walking along a straight line, e.g.
the x-axis. She starts at x = 40. She moves in
Steps of one unit along the line. Each step is to
the left or the right with equal probability. We
would like a visual representation of how much
time she spends at each position.
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8. MATLAB Code bar(f) f = zeros(1,100); x = 40; for i = 1:1000 r = rand;
if r >= 0.5
x = x + 1;
else
x = x - 1;
end
f(x) = f(x) + 1;
End
bar(f)
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9. hist()
What is a histogram? his·to·gram, ˈhistəˌɡram/ Noun, STATISTICS a diagram consisting of rectangles whose area is proportional to the frequency of a variable and whose width is equal to the class interval.
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10. Exercise
Use vectorization and hist() function to repeat the exercises on flipping a coin and rolling a die.
Increase the number of trials to 1000, 10,000 and 1,000,000.
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11. Exercise
Generate row vector (128 elements) of random numbers between 0 and 1 and use imshow() to visualize it. Then use hist() function to see the distribution.
Repeat the above for vector sizes 256, 512 and 1024 and draw a conclusion regarding the size of the vector.
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12. Arrays of characters: strings
Assignment:
s = ’Hi there’;
s = ’o’’clock’;
Input:
name = input(‘Enter Your Name:’)
Enter Your Name: ’myname’
name = input(‘Enter Your Name:’,’s’)
Enter Your Name: myname
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13. Strings are arrays s = ’Napoleon’ s(8:-1:1) Concatenation of strings
king = ’Henry’;
king = [king, ’ VIII’]
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14. ASCII Table
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15. ASCII code Exercise Decode from ASCII to string: 69 71 69 45 51 51 49
What are the ASCII codes for:
Carriage Return
Linefeed
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16. ASCII codes,double and char
double(’Napoleon’)
char(65:70)
ABCDEF
x = char(ones(4,20)*double(’#’))
####################
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17. Exercise
Write a program that prints all ASCII codes along with their corresponding characters in a single column.
Show the above table in a multi-column form.
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18. ASCII codes,double and char
s = ’a’
s+1
char(s+1)
alpha = double(’a’):double(’z’)
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19. Comparing strings s1 = ’ann’; s2 = ’ban’; s1 < s2 1 0 0
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20. Other string functions
blanks
generates a string of blanks.
deblank
removes trailing blanks from a string.
int2str, num2str
convert their numeric arguments to strings.
ischar
returns 1 if its argument is a string, and 0 otherwise.
lower, upper
convert strings to lower- and uppercase respectively
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21. Exercise
Prompt the user to enter his/her name: First name separated from the last name by a blank. Print out the a string starting with the last name separated from the first name by a coma. Capitalize the first characters of the first and last names.
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22. Matlab Code s = input('Enter Your Name(John Doe):','s')
for i=1:length(s)
if s(i) == ' '
s(1) = upper(s(1));
s(i+1)=upper(s(i+1));
s1=[s(i+1:length(s)),', ',s(1:i-1)]
break;
end
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23. fprintf, fprintf( ’% 8sVIII\n’, ’Henry’ )
ؙؙؙHenryVIII
Henry ؙؙؙ VIII
HenVIII
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24. sprintf Value of K: .015 K=.015 s = sprintf( ’Value of K: %g’, K )
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25. Two-dimensional strings
nameAndAddress = [’Adam B Carr ’; ’21 Barkly Ave’; ’Discovery ’]
nameAndAddress =
Adam B Carr
21 Barkly Ave
Discovery
nameAndAddress = char(’Adam B Carr’, ’21 Barkly Ave’, ’Discovery’)
double(nameAndAddress(1,12))
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26. Eval and text macros s = ’x = -b/(2*a);’ eval(s) x = -b/(2*a);
Have the user enter a matlab function, such as sin(x), cos(x), etc. Your program should plot that function.
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27. Code f = input( ’Enter function (of x) to be plotted: ’, ’s’ );
plot(x, eval(f)),grid
Enter function (of x) to be plotted: exp(-0.5*x) .* sin(x)
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