for – while – switch

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for – while – switch

ผศ.ดร.อนั�นัต์ ผลเพิ่��มAnan Phonphoem

http://www.cpe.ku.ac.th/~anananan@cpe.ku.ac.th

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Loops

Repeating a calculation for a number of times

Each repetition of the loop is a pass Two types of loops (In MATLAB)

for loop while loop

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for loops

for loop var = m:s:n statementsend

Variable > nTrue

False

Increment variable by s

Set loop variable = m

Statements

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for loops (Example)

for a = 1:2:10 total = total + aend

a > 10True

False

a = a + 2

a = 1

total = total +a

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break command

To abnormally jump out of the loop before its end

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Find the answer of the program

for num = 10:-2:0 disp(num); temp = 2*num - 10; solution = temp + 5;endsolution = solution - 10

>> cmd1 10 8 6 4 2 0

solution = -15

Resultscmd1.m

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break example

% showing ‘break’ commandfor num = 10:-2:0 disp(num); temp = 2*num - 10; if (temp <= 0) break end solution = temp + 5;endsolution = solution - 10

>> cmd2 10 8 6 4

solution = -3

Resultscmd2.m

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continue command

To skip for some cases and continue execute the rest of the loop

For example, skip the error that might happen

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continue example

a = [100 0 10 -10];for k = 1:length(a) solution = 1000/a(k)end

>> cmd3solution = 10Warning: Divide by zero.> In cmd3 at 3solution = Infsolution = 100solution = -100

Resultscmd3.m

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continue example

% showing ‘continue’ commanda = [100 0 10 -10];for k = 1:length(a) if (a(k)== 0) continue end solution = 1000/a(k)end

>> cmd4solution = 10

solution = 100

solution = -100

Resultscmd4.m

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while loop

Looping process is terminated based on the specified condition

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conditionFalse

True

Statements

while loops

while condition statementsend

Set loop variable = m

Increment variableWithout the , no way to get out of the loop.

It’s called “infinite loop”

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while example (I)

while k > 0 disp(k);end

>> cmd5??? Undefined function or variable "k".

Error in ==> cmd5 at 1while k > 0

Results

cmd5.m

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while example (II)

k = 5;while k > 0 disp(k);end

>> cmd6 5 5 5 5 …

Results

cmd6.m

To break the programPress “Ctrl-C”

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while example (III)

k = 5;while k > 0 disp(k); k = k-1;end

>> cmd7 5 4 3 2 1

Resultscmd7.m

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while and for loop

% showing ‘break’ commandfor num = 10:-2:0 disp(num); temp = 2*num - 10; if (temp <= 0) break end solution = temp + 5;endsolution = solution - 10

cmd2.m Rewrite the programBy using “while”

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while and for loop

% using whilenum = 10;temp = 2*num - 10; while temp > 0 disp(num); solution = temp+5; temp = 2*num -10; num = num-2;endsolution = solution - 10

cmd8.m

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Nested Logic

condition1 FalseTrue

Statement1condition2

FalseTrue

Statement3Statement2

if logical exp1 statement g1elseif logical exp2 statement g2else statement g3end

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if-else and switch comparison

switch input expression case value1 statement g1 case value2 statement g2 otherwise statement g3end

if logical exp1 statement g1elseif logical exp2 statement g2else statement g3end

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Nested Logic – (Example)

a == 20 FalseTrue

c = a * 2 c == 30

FalseTrue

c = 0c = a + 2

if a == 20 c = a * 2elseif a == 30 c = a + 2else c = 0 end

switch a case 20 c = a * 2 case 30 c = a + 2 otherwise c = 0 end

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switch

switch input expression case value1 statement group 1 case value2 statement group 2 case value1 statement group 3 ... otherwise statement group nend

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switch example (I)

response = input(‘Type like, hate, or ok: ’,’s’);switch response case ‘like’ disp(‘I really like it’); case ‘hate’ disp(‘I do not like it’); case ‘ok’ disp(‘It is ok’); otherwise disp(‘Your enter is wrong’);end

cmd9.m

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switch example (I)

>> cmd9Type like, hate, or ok: likeI really like it>> cmd9Type like, hate, or ok: hateI do not like it>> cmd9Type like, hate, or ok: abcYour enter is wrong >> cmd9Type like, hate, or ok: LikeYour enter is wrong

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Can you make it better ?

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while true response = input(‘Type like,hate,ok, or quit:’,’s’); response = lower(response); switch response case ‘like’ disp(‘I really like it’); case ‘hate’ disp(‘I do not like it’); case ‘ok’ disp(‘It is ok’); case ‘quit’ break otherwise disp(‘Your enter is wrong’); end %end switchend %end while

switch example (II)cmd10.m

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switch example (II)

>> cmd10Type like, hate, ok, or quit: likeI really like itType like, hate, ok, or quit: HateI do not like itType like, hate, ok, or quit: abcYour enter is wrongType like, hate, ok, or quit: quit>>