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# if-elseif-else statements Switch-case-otherwise For loops by kaj11697

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```									               COMP319 INTRODUCTION TO MULTI-MEDIA COMPUTING

Lab 3: Execution Control

if-elseif-else statements:
i = 6; j=21;
if i > 5
k=i;
elseif (i>1) & (j==20)
k = 5*i+j;
else
k=1;
end

Switch-case-otherwise:
color = input(‘color = ‘ ,’s’)
switch color
case ‘red’
c = [1 0 0]
case ‘green’
c = [ 0 1 0]
case ‘blue’
c = [0 0 1]
otherwise
error(‘invalid choice of color’)
end

For loops: repeat a statement for a fixed number of times
for m=1:100
num = 1/ (m+1)
end

for n=100:-2:0, k = 1/(exp(n)), end

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While loops: execute a statement for an indefinite number of times until the
condition is longer satisfied.
% let us find all powers of 2 below 10000
v = 1; num = 1; i=1;
while num < 10000
num = 2^i;
v = [v; num];
i = i +1;
end

Break
x= exp(sqrt(163));
while 1
n = input(‘Enter max. number of iterations ‘)
if n <=0
break;      %terminate loop execution
end
for i = 1:n
x = log(x); %do something
end
end

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Exercise:
1.    Write a script that uses input(…) to request a numerical grade in percentage and uses if
statements to convert that grade to a letter grade according to the following table:

90% and better: A
80%-90%: B
70%-80%: C
60%-70%: D
Below 60%: F

Test your script by running it repeatedly for legal and illegal values of the grade percentage.

Repeat the exercise using switch statement

2. *Write a script file named sineseries.m that computes the value of sin(x) at a given x using n
terms of the series expansion of sine function:
����
���� 3 ���� 5                           ���� 2����−1
sin ���� = ���� − + − ⋯ =                (−1)����−1
3! 5!                              2���� − 1 !
����=1

    First, query MATLAB to see if the name ‘sineseries’ is already taken by some variable or
function with the command exist(sineseries). What does the MATLAB response mean?
[Hint see on-line help on exist. i.e. help exist]
    Include the following line as the header (H1 line) of your script file.
%SINESERIES: computes sin(x) from series expansion
Now code the formula so that it computes the sum of the series for a given scalar x and a
given integer n.
    Save the file. Type help sineseries to see if MATLAB can access your script file. Now,
compute sin(pi/6) with n = 1,5,10, and 20. Compute the results. Do the same for some other