Chapter 6 Programming in Matlab

7/23/2019 Chapter 6 Programming in Matlab

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Slide deck by

Dr. Greg ReeseMiami University

Chapter 6Programming in MATLAB


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#n t$is c$a%ter &ill st'dy $o&to make MATLAB %rogramsr'n sections o( code

#( somet$ing is tr'e

)$ile somet$ing is tr'e

*or a certain n'mber o(times


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!."

)ill also learn $o& to r'n

di,erent sections o( codede%ending onT$e val'e o( a variable

)$ic$ %artic'lar condition is tr'e )$at combination o( conditions istr'e

#( t$is and t$at are tr'e#( t$is or t$at is tr'e- etc.

)$at relations$i% t&o t$ings $ave

*or eam%le- one is less t$an t$e


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!.1 R2LAT#34AL A4D L3G#5AL3P2RAT3RS

Relational operator:

5an6t %'t s%ace bet&een o%erators t$at$ave t&o c$aracters

74ot e0'al to7 is 7897- not 7:97 as in 5or 5;;

720'al to7 com%arison is t&o e0'alsigns


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Res'lt o( com%aring &it$ arelational o%erator is al&ays 7tr'e7

or 7(alse7#( 7tr'e7- MATLAB gives t$e

com%arison a val'e o( one


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)$en com%aring arraysT$ey m'st be t$e samedimensions

MATLAB does an element@&isecom%arison

Res'lt is an array t$at $as

same dimensions as ot$er t&ob't only contains 16s and "6s


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)$en com%aring array toscalar

MATLAB com%ares scalar toevery member o( array

Res'lt is an array t$at $as

same dimensions as originalb't only contains 16s and "6s


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2am%le

>> x=8:12

x = 8 9 10 11 12

>> x>10

ans = 0 0 0 1 1

>> x==11

ans = 0 0 0 1 0

>> x>=7

ans = 1 1 1 1 1


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#t $el%s to %ict're in yo'r mind t$at

t$e res'lt o( a logical com%arison1. #s a vector

. as a " or 1 corres%onding to eac$original element

>> x=8:12

x = 8 9 10 11 12

>> x>10

ans = 0 0 0 1 1

T # P


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#( res'lts o( relationalcom%arison stored in a vector-can easily End t$e n'mber o(

elements t$at satis(y t$atcom%arison- i.e.- t$at are tr'e-by 'sing sumcommand- &$ic$

ret'rns s'm o( vector elements )orks beca'se elements t$at aretr'e $ave val'e o( one and (alse

elements $ave val'e ?ero

T # P


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2FAMPL2

o& many o( t$e n'mbers (rom1@" are %rime Use MATLAB isprimecommand-

&$ic$ ret'rns tr'e


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5an mi relational and

arit$metic o%erations in onee%ression Arit$metic o%erations (ollo& 's'al

%recedence and al&ays $ave$ig$er %recedence t$an relationalo%erations

Relational o%erations all $avee0'al %recedence and eval'atedle(t to rig$t

T # P


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A logical vectoror logical array

is a vectorHarray t$at $as onlylogical16s and "6s

16s and "6s (rom mat$ematicalo%erations don6t co'nt

16s and "6s (rom relational

com%arisons do &ork *irst time a logical vectorHarray'sed in arit$metic- MATLAB

c$anges it to a n'merical


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5an 'se logical vector to get

act'al val'es t$at satis(y relation-not I'st &$et$er or not relationsatisEed. Doing t$is is called

logical indexingor logicalsubscripting Do t$is by 'sing logical vector as

inde in vector o( val'es. Res'lt isval'es t$at satis(y relation- i.e.-val'es (or &$ic$ relations$i% are 1

43T2 J tec$ni0'e doesn6t 0'ite &ork &it$

arrays. )on6t disc'ss t$at case ('rt$er


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2FAMPL2

)$at are t$e n'mbers (rom 1@1"t$at are m'lti%les o( +>> numbers = 1:10

numbers = 1 2 3 4 5 6 7 8 9 10>> multiples = rem( numbers, 3 ) == 0

multiples = 0 0 1 0 0 1 0 0 1 0

>> multiples!3 = numbers(multiples)multiples!3 =

3 6 9


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2am%le

T$ink o( numbers(multiples)as%'lling o't o( numbersall elementst$at $ave a 1in t$e corres%onding

element o( multiplesnumbers = 1 2 3 4 5 6 7 8 9 10

multiples = 0 0 1 0 0 1 0 0 1 0

numbers(multiples) = 3 6 9


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2FAMPL2

)$at are t$e %rime n'mbers (rom1@">> numbers = 1:20;

>> numbers( isprime(numbers) )

ans =

2 3 5 7 11 13 17 19

Logical indeing is %artic'larly'se('l &$en 'sed &it$ logical

o%erators- disc'ssed net


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Logical operators:

Boolean logic is a system (orcombining e%ressions t$at areeit$er tr'e o( (alse.

MATLAB $as o%erators andcommands to do many Booleano%erations

Boolean o%erations incombination &it$ relationalcommands let yo' %er(ormcertain t es o( com 'tations


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A truth table deEnes t$e la&s o(

Boolean logic. #t gives t$e o't%'t o(a logical o%eration (or every%ossible combination o( in%'ts. T$e

tr't$ table relevant to MATLAB is


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#n &ords- t$e tr't$ table says A4D is tr'e i( bot$ in%'ts aretr'e- ot$er&ise it is (alse

3R is tr'e i( at least one in%'t is

tr'e- ot$er&ise it is (alse

F3R


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An arit$metic o%erator- e.g.- ; or

@- is a symbol t$at ca'ses MATLABto %er(orm an arit$meticalo%eration 'sing t$e n'mbers or

e%ressions on eit$er side o( t$esymbol.

Similarly- a logical operatoris ac$aracter t$at makes MATLAB%er(orm a logical o%eration on one

or t&o n'mbers or e%ressions.


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MATLAB $as t$ree logical o%erators

"- #- $ a"bdoes t$e logical A4D o%eration on aand b

a#bdoes t$e logical 3R o%eration on aor b

$a does t$e logical 43T o%eration on a

Arg'ments to all logical o%erators aren'mbersero is 7(alse7

Any non@?ero n'mber is 7tr'e7

! 1 R2LAT#34AL A4D L3G#5AL


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)$en 'sing logical o%erator onarraysT$ey m'st be t$e same dimensions

MATLAB does an element@&iseeval'ation o( o%erator

Res'lt is an array t$at $as samedimensions as ot$er t&o b't onlycontains 16s and "6s


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)$en o%erating &it$ array andscalar

MATLAB does element@&iseo%eration on eac$ array element&it$ scalar

Res'lt is an array t$at $as samedimensions as original b't onlycontains 16s and "6s



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5an combine arit$metic-

relational o%erators- and logicalo%erators. 3rder o( %recedenceis



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2FAMPL2

5$ild J 1 or less yearsTeenager J more t$an 1 and less t$an

" years

Ad'lt J " or more years>> a&e='45 47 15 13 11

a&e = 45 47 15 13 11



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2FAMPL2

)$o is a teenager>> a&e='45 47 15 13 11;

>> a&e>=13

ans = 1 1 1 1 0

>> a&e=19

ans = 0 0 1 1 1

>> a&e>=13 " a&e=19

ans = 0 0 1 1 0

T$ese mark t$e t&o



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2FAMPL2

>> a&e='45 47 15 13 11a&e = 45 47 15 13 11

)$o is not a teenager

>> $(a&e>=13 " a&e=19)

ans = 1 1 0 0 1

)$o is an ad'lt or a c$ild

>> a&e>19 # a&e13

ans = 1 1 0 0 1



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Built-in logical functions:

MATLAB $as some b'ilt@in('nctions or commands (or doinglogical o%erations and related

calc'lations. T$ree are e0'ivalentto t$e logical o%erators

an*(+,)J same as +"

%r(+,)J same as +#

n%t(+)J same as $+



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MATLAB also$as ot$er

Boolean('nctions

! 534D#T#34AL


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!. 534D#T#34ALSTAT2M24TS

A conditional statementis a

command t$at allo&s MATLABto decide &$et$er or not toeec'te some code t$at (ollo&s

t$e statement 5onditional statements almostal&ays %art o( scri%ts or ('nctions

T$ey $ave t$ree general (ormsi!-en*

i!-else-en*

i!-elsei!-else-en*

! 1 T$e i!-en*


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!..1 T$ei!-en*Str'ct're

An i!-en*statement $as t$e (orm

i! conditional@e%ression

code line 1

code line

en*

remaining lines o( code

#( t$e conditional e%ression is tr'e-MATLAB r'ns t$e lines o( code t$at arebet&een t$e line &it$ i! and t$e line&it$ en*. T$en it contin'es &it$ t$e codea(ter t$e en*@line

5an be any n'mber o( lines o(code

! 1 T$e i!-en*


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!..1 T$ei! en*Str'ct're


code line 1code line

en*


#( t$e conditional e%ression is (alse-

MATLAB ski%s t$e lines o( code t$at arebet&een t$e line &it$ i! and t$e line&it$ en*. T$en it contin'es &it$ t$e

code a(ter t$e en*@line


! 1 T$e i!-en*


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en*


T$e conditional e%ression is tr'e i( it

eval'ates to a logical 1 or to a non@?eron'mber. T$e conditional e%ression is(alse i( it eval'ates to a logical " or to a

n'merical ?ero.


! 1 T$e i!-en*


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%receding code



en*

(ollo&ing code

T$e above s$o&s t$e i!-en*

statement in a &ay t$at em%$asi?es&$at t$e contents o( t$e lines o(code. To em%$asi?e t$e code fow-i.e.- t$e order in &$ic$ t$e code iseec'ted- can 'se a No&c$art

!..1 T$e i!-en*


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A fowchartis a diagramt$at s$o&s t$e code No&.Some common No&c$artsymbols are

re%resents a se0'ence o(commands

re%resents an i(@statement s$o&s t$e direction o(code eec'tion

!..1 T$e i!-en*


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*ig. !@1 s$o&s t$e i(@end str'ct're asbot$ lines o( code and a No&c$art.

4ote $o& t$e diamond symbolclearly s$o&s t$at t$e code No& isdi,erent i( t$e conditional

e%ression is tr'e t$an i( it is (alse

!.. T$ei!-else-en*


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Str'ct're

i!-else-en*str'ct're lets yo'

eec'te one section o( code i( acondition is tr'e and a di,erentsection o( code i( it is (alse.

2FAMPL2 @ ans&ering yo'r %$onei! t$e caller is yo'r best (riend

talk (or a long time

elsetalk (or a s$ort time

en*

!.. T$ei!-else-en*


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Str'ct're

*ig. !@ s$o&s t$e code andt$e No&c$art (or t$e i!-else-en*str'ct're

!..+ T$ei!-elsei!-else-en*


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Str'ct're

i!-elsei!-else-en*str'ct're lets

yo' c$oose one o( t$ree


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Str'ct're

5an $ave as many elsei!statements asyo' &ant

2FAMPL2i! t$e caller is yo'r best (riend


elsei!t$e caller is a %otential date

talk (or a little bit and t$en set a time to meet

elsei!t$e caller is yo'r st'dy@mate

talk 'ntil yo' get t$e ans&er to t$e $ard

%roblemelsei!t$e caller is yo'r mom

say yo'6re b'sy and can6t talk

else

$ave yo'r room@mate say yo'6ll call back later



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Str'ct're

*ig. !@+ s$o&s t$e code and t$eNo&c$art (or t$e i!-elsei!-else-en*str'ct're



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Str'ct're

5an omit elsestatement

#n t$is case- i( no matc$ toi!@ or elsei!@statements-no code in str'ct're gets

eec'ted

!.+ T2 s.it/-/ase


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STAT2M24T

i!-elsei!-else-en*str'ct're

gets $ard to read i( more t$an a(e& elsei!statements. Aclearer alternative is t$e

s.it/-/asestr'ct'res.it/-/aseslig$tly di,erentbeca'se c$oose code to

eec'te based on val'e o(scalar or string- not I'sttr'eH(alse

!.+ T2 s.it/-/ase


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STAT2M24T

5once%t iss.it/ name

/ase %bb


/ase usan

talk (or a little bit and t$en set a time to

meet

/ase ubert

talk 'ntil yo' get t$e ans&er to t$e $ard%roblem

/ase %m

say yo'6re b'sy and can6t talk

%ter.ise

$ave yo'r room@mate say yo'6ll call backlater

!.+ T2 s.it/-/ase


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!

STAT2M24T

!.+ T2 s.it/-/aseSTAT2M24T


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STAT2M24T

s.it/eval'atess&itc$@e%ression#( val'e is e0'al toalue1- eec'tesall commands '% to

net /ase-%ter.ise,

or en*statement- i.e.- Gro'% 1commands- t$en eec'tes code a(ter

en*statement#( val'e is e0'al to alue2- same as

above b't Gro'% commands only

2tc.



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STAT2M24T#( s&itc$@e%ression not

e0'al to any o( val'es in/asestatement-commands a(ter%ter.iseeec'ted. #(%ter.isenot %resent-

no commands eec'ted #( s&itc$ e%ression matc$es more t$anone /aseval'e- only Erst matc$ing/aseeec'ted



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STAT2M24T

5om%arisons o( tet strings are case@sensitive. #( /aseval'es are tet

strings- make all val'es eit$er lo&ercase or '%%er case- t$en 'se upperorl%.ercommand to convert s&itc$e%ression

/aller = l%.er( name );

s.it/ /aller

/ase b%bb

some code

/ase susan

some code

/ase m%m

some code

T # P

!.L33PS


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L33PS

A loopis anot$er met$od o(

No& control. A loo% eec'tesone set o( commandsre%eatedly. MATLAB $as t&o

&ays to control n'mber o(times loo% eec'tes commands Met$od 1 J loo% eec'tescommands a s%eciEed n'mber o(times

Met$od J loo% eec'tes

commands as long as a s%eciEed

!..1 !%r-en*Loo%s


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Loo%s

A !%r-en*loo%


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Loo%s

T$e loo% inde variable can $ave anyvariable name


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Loo%s

1. Loo% sets to !-and eec'tescommands bet&een!%rand t$e en*commands-i.e.- eec'tes body o( loo%

. Loo% sets to !s- eec'tes body+. Process re%eats itsel( 'ntil > t

. Program t$en contin'es &it$ commandst$at (ollo& en*command

.!and tare 's'ally integers

.s's'ally omitted. #( so- loo% 'sesincrement o( 1

Body o(loo%

!..1 !%r-en*Loo%s


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Loo%s

#ncrement scan be negative*or eam%le- = 25:5:10%rod'ces

(o'r %asses &it$ = 25, 20, 15, 10

#( ! = t- loo% eec'tes once

#( ! > tand s > 0- or i( ! t ands 0,loo% not eec'ted

Body o(loo%

!..1 !%r-en*Loo%s


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>>

Loo%s

#( val'es o( - s- and tare s'c$ t$at

cannot be e0'al to t- t$en#( s%ositive- last %ass is one &$ere $as

largest val'e smaller t$an t

*or eam%le- = 8:10:50%rod'ces Eve%asses &it$ = 8, 18, 28, 38, 48

#( s is negative- last %ass is one &$ere $as smallest val'e larger t$an t

Body o(loo%

!..1 !%r-en*Loo%s


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Loo%s

#n t$e !%rcommand can also be

assigned s%eciEc val'e


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Loo%s

Oal'e o( loo% inde variable


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Loo%s

2FAMPL2

Scri%t!%r =1:3:10

x = 2

en*

!print!(+!ter l%%p = *


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Loo%s

5an o(ten calc'latesomet$ing 'sing eit$er a (or@

loo% or element&iseo%erations.

2lement&ise o%erations are 3(ten (aster

3(ten easier to read

More MATLAB@likeG242RAL ADO#52 J 'seelement&ise o%erations &$en

yo' can- (or@loo%s &$en yo'

T # P

!.. .ile-en*Loo%s


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Loo%s

.ile-en*loo% 'sed &$en

o' don6t kno& n'mber o( loo%iterations

o' do $ave a condition t$at yo'

can test and sto% loo%ing &$en itis (alse. *or eam%le-Qee% reading data (rom a Ele 'ntil

yo' reac$ t$e end o( t$e Ele

Qee% adding terms to a s'm 'ntil t$edi,erence o( t$e last t&o terms isless t$an a certain amo'nt

!.. .ile-en*Loo%s


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Loo%s

1. Loo%

eval'atesconditional@e%ression

. #( conditional@e%ression is

tr'e- eec'tes code in body-t$en goes back to Ste% 1

+. #( conditional@e%ression is

(alse- ski%s code in body andgoes to code a(ter en*@statement

!.. .ile-en*Loo%s


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!

oo%s

T$e conditional e%ression o( a.ile-en*loo%

as a variable in itBody o( loo% m'st c$ange val'e o(variable

T$ere m'st be some val'e o( t$e

variable t$at makes t$e conditionale%ression be (alse

!.. .ile-en*Loo%s


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!+

%

2FAMPL2

T$is scri%tx = 1

.ile x = 15

x = 2xen*

Makes t$is

o't%'tx =

1

x =

2

x =

4

x =

8

x =

16

!.. .ile-en*Loo%s


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!

%

#( t$e conditional e%ression

never becomes (alse- t$e loo%&ill kee% eec'ting... (orever:

T$e book calls t$is an indenite

loop, b't more commonlyre(erred to as an innite loop.

o'r %rogram &ill I'st kee%

r'nning- and i( t$ere is no o't%'t(rom t$e loo%


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%

5ommon ca'ses o( indeEnite loo%s 4o variable in conditional e%ression

*istan/e1 = 1;

*istan/e2 = 10;*istan/e3 = 0;

.ile *istan/e1 *istan/e2

!print!(istan/e = *


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!!

%

5ommon ca'ses o( indeEnite loo%s Oariable in conditional e%ressionnever c$anges

ministan/e = 42;

*istan/e?n/rement = 0;

*istan/e = 0;

.ile *istan/e ministan/e

*istan/e=*istan/e*istan/e?n/rement;en*

Ty%o J s$o'ld be1"

!.. .ile-en*Loo%s


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5ommon ca'ses o( indeEnite

loo%s )rong variable in conditionale%ression c$anged

ministan/e = 42;*elta = 10;

*istan/e = 0;

.ile *istan/e ministan/e

ministan/e = ministan/e *elta;

en* Ty%o J s$o'ld bedistance

!.. .ile-en*Loo%s


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5ommon ca'ses o( indeEniteloo%s 5onditional e%ression neverbecomes (alse

ministan/e = 42;

x = 0;

= 0;

.ile -s@rt( x22 ) ministan/e

x = x 1;

= x;

en*

Ty%o J s$o'ldn6t beany negative sign

!.. .ile-en*Loo%s


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#( yo'r %rogram gets ca'g$tin an indeEnite loo%-

P't t$e c'rsor in t$e5ommand )indo&

Press 5TRL;5

T # P

!.> 42ST2D L33PS A4D 42ST2D 534D#T#34ALSTAT2M24TS


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#( a loo% or conditional

statement is %laced insideanot$er loo% or conditionalstatement- t$e (ormer are said

to be nestedin t$e latter. Most common to $ear o( a nestedloop- i.e.- a loo% &it$in a loo%

3(ten occ'r &$en &orking &it$ t&o@dimensional %roblems

2ac$ loo% and conditionalstatement m'st $ave an en*

!.> 42ST2D L33PS A4D 42ST2D 534D#T#34ALSTAT2M24TS


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1

2FAMPL2

!.! T2 breaA4D /%ntinue53MMA4DS


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The breacommand:

)$en inside a loo%


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breacommand in scri%t or ('nctionEle b't not in a loo% terminateseec'tion o( Ele

breacommand 's'ally 'sed &it$ina conditional statement.#n loo%s %rovides &ay to end loo%ing i(

some condition is met

!.! T2 breaA4D /%ntinue53MMA4DS

2FAMPL2


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2FAMPL2Scri%t

.ile( 1 ) name = input( Ape name %r @ t% @uit: , s );

i! len&t( name ) == 1 "" name(1) == @

brea;

else

!print!( B%ur name is s


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The /%ntinuecommand:

Use /%ntinueinside a loo%


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2FAMPL2!%r ii=1:100

i! rem( ii, 8 ) == 0

/%unt = 0;

!print!(ii=*

Documents

Chapter 6 Programming in Matlab