Matlab: A Practical Introduction to Programming and Problem Solving, Second Edition

522 Pages·2011·7 MB·English

by  Stormy Attaway

W
MATLAB
A Practical Introduction
to Programming and
Problem Solving
Second Edition
W
MATLAB
A Practical Introduction
to Programming and
Problem Solving
Second Edition
Stormy Attaway
Department of Mechanical Engineering
Boston University
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particularpedagogicalapproachorparticularuseoftheMATLABWsoftware.
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LibraryofCongressCataloging-in-PublicationData
Attaway,Stormy.
MATLABW:apracticalintroductiontoprogrammingandproblemsolving/Stormy
Attaway.—2nded.
p. cm.
Includesindex.
ISBN978-0-12-385081-2
1.Numericalanalysis—Dataprocessing.2.MATLAB.3.Computerprogramming.
I.Title.
QA297.A872011
518.028553—dc22 2011015032
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ForinformationonallButterworth–Heinemannpublications
visitourWebsiteatwww.elsevierdirect.com
PrintedintheUnitedStates
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Thisbookis dedicatedto my husband, TeddeWinter.
Preface
Motivation
Thepurposeofthisbookistoteachfundamentalsofprogrammingconceptsand
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skills needed for basic problem solving, all using MATLAB as the vehicle.
MATLABisapowerfulsoftwarepackagethathasbuilt-infunctionstoaccomplish
a diverse range of tasks, from mathematical operations to three-dimensional
imaging.Additionally,MATLABhasacompletesetofprogrammingconstructs
thatallowsuserstocustomizeprogramstotheirownspecifications.
ThemanybooksthatintroduceMATLABcomeintwobasicflavors:thosethat
demonstratetheuseofthebuilt-infunctionsinMATLAB,withachapterortwo
onsomeprogrammingconcepts;andthosethatcoveronlytheprogramming
constructs without mentioning many of the built-in functions that make
MATLAB efficient to use. Someone who learns just the built-in functions will
be well-prepared to use MATLAB, but would not understand basic program-
ming concepts. That person would not be able to then learn a language such
asCþþorJavawithouttakinganotherintroductorycourseorreadinganother
bookontheprogrammingconcepts.Conversely,anyonewholearnsonlypro-
grammingconceptsfirst(usinganylanguage)wouldtendtowritehighlyinef-
ficient code using control statements to solve problems, not realizing that in
many casesthese are not necessary inMATLAB.
Thisbookinsteadtakesahybridapproach,introducingboththeprogramming
and efficient uses. The challenge for students is that it is nearly impossible to
predict whether they will in fact need to know programming concepts later
or whether a software package such as MATLAB will suffice for their careers.
Therefore, the best approach for beginning students is to give them both: the
programming concepts and the efficient built-in functions. Since MATLAB is
veryeasytouse,itisaperfectplatformforthisapproachtoteachingprogram-
ming and problem solving.
Sinceprogrammingconceptsarecriticallyimportanttothisbook,emphasisis
notplacedonthetime-savingfeaturesthatevolvewitheverynewMATLABre-
lease. For example, in current versions of MATLAB, statistics on variables are
xi
xii Preface
availablereadilyintheWorkspaceWindow.Thisisnotshowninanydetailin
the book, since whether this featureis available depends on the software ver-
sion, and because of thedesire to explain the concepts in the book.
Modifications in Second Edition
Changesin the second edition ofthis book include:
n Vectorized code hasbeenmade into aseparatechaptertoemphasize the
importance ofusing MATLABefficiently.
n There are expanded exampleson:
n Low-level file input functions
n Plots
n Graphical user interfaces
n Vectorized code,including functions diff, meshgrid,tic,and toc
n Use of MATLABversion R2011a
n Conceptsusedinimageprocessing,suchasthree-dimensionalmatricesand
unsigned integers,are now introducedearly, inChapter 1.
n Modified and new end-of-chapterexercises.
n TheintroductiontoHandleGraphicswasmovedtoChapter11,Advanced
Plotting Techniques.
n DiscussionofsymbolicmathematicswasmovedtoChapter15,Advanced
Mathematics.
n Improvedlabeling ofplots.
n Improvedstandards for variablenames and documentation.
n Added end tothe endof all functions.
Key Features
Side-by-Side Programming Concepts and Built-in Functions
Themostimportant,andunique,featureofthisbookisthatitteachesprogram-
mingconceptsandtheuseofthebuilt-infunctionsinMATLABsidebyside.It
startswithbasicprogrammingconceptssuchasvariables,assignments,input/
output,selection,andloopstatements.Thenthroughouttherestofthebook,
manytimesaproblemwillbeintroducedandthensolvedusingthe“program-
mingconcept”andalsousingthe“efficientmethod.”Thiswillnotbedonein
everycasetothepointthatitbecomestedious,butjustenoughtogettheideas
across.
Systematic Approach
Another key feature is that the book takes a very systematic, step-by-step ap-
proach, building on concepts throughout the book. It is very tempting in a
MATLAB text to show built-in functions or features early on with a note that
says “we’ll do this later.” This does not happen in this edition; all functions
arecoveredbeforetheyareusedinexamples.Additionally,basicprogramming
Preface xiii
conceptswillbeexplainedcarefullyandsystematically.Verybasicconcepts,such
asloopingtocalculateasum,countinginaconditionalloop,anderror-checking,
arenotfoundinmanytextsbutwillbecoveredhere.
File Input/Output
Manyapplicationsinengineeringandthesciencesinvolvemanipulatinglarge
datasetsthatarestoredinexternalfiles.MostMATLABtextsatleastmentionthe
saveandloadfunctions,andinsomecasesselectedlower-levelfileinput/out-
putfunctionsaswell.Sincefileinputandoutputissofundamentaltosomany
applications,thisbookwillcoverseverallow-levelfileinput/outputfunctions,
aswellasreadingfromandwritingtospreadsheetfiles.Laterchapterswillalso
deal with audio and image files. These file input/output concepts are intro-
duced gradually: first load and save in Chapter 2, then lower-level functions
inChapter 9, and finallysound and images inChapter 14.
User-Defined Functions
User-defined functions are a very important programming concept, and yet
manytimesthenuancesanddifferencesamongconceptssuchastypesoffunc-
tionsandfunctioncallsversusfunctionheaderscanbeveryconfusingtobegin-
ning programmers. Therefore, these concepts are introduced gradually. First,
functionsthatcalculateandreturnonesinglevalue—arguablytheeasiesttype
of functions to understand—are demonstrated in Chapter 2. Later, functions
thatreturnnovaluesandfunctionsthatreturnmultiplevaluesareintroduced
inChapter 6. Finally, advanced function features are shownin Chapter10.
Advanced Programming Concepts
Inadditiontothebasics,someadvancedprogrammingconcepts,suchasstring
manipulation,datastructures(e.g.,structuresandcellarrays),recursion,anon-
ymousfunctions,andvariablenumberofargumentstofunctions,arecovered.
Sorting, searching, and indexing are also addressed. All of these are again
approached systematically; for example, cell arrays are covered before they
are used infile input functions and as labels on piecharts.
Problem-Solving Tools
In addition to the programming concepts, some basic mathematics necessary
for solving many problems will be introduced. These will include statistical
functions,solvingsetsoflinearalgebraicequations,andfittingcurvestodata.
The use of complex numbers and some calculus (integration and differentia-
tion) will also be introduced. The basic math will be explained and the
built-infunctions inMATLAB toperform these tasks will be described.
xiv Preface
Plots, Imaging, and Graphical User Interfaces
Simple two-dimensional plots are introduced very early in the book in
Chapter 2 so that plot examples can be used throughout. Chapter 11 then
shows more plot types, and demonstrates customizing plots and how the
graphicspropertiesarehandledinMATLAB.Thischaptermakesuseofstrings
andcellarraystocustomizelabels.Also,thereisanintroductiontoimagepro-
cessingandthebasicsnecessarytounderstandprogramminggraphicaluserin-
terfaces(GUIs) in Chapter 14.
Vectorized Code
Efficient uses of the capabilities of the built-in operators and functions in
MATLABaredemonstratedthroughoutthebook.However,toemphasizetheim-
portance of using MATLAB efficiently, vectorized code is treated in a separate
chapter. Techniques, such as preallocating vectors and using logical vectors,
arefeatured,aswellasmethodsofdetermininghowefficientthecodeis.
Layout of Text
The book consists of two parts. The first part covers programming constructs
and demonstrates the programming method versus efficient use of built-in
functionstosolveproblems.Thesecondpartcoverstoolsthatareusedforbasic
problemsolving,includingplotting,imageprocessing,andmathematicaltech-
niquestosolvesystemsoflinearalgebraicequations,fitcurvestodata,andper-
form basic statistical analyses. The first six chapters cover the very basics in
MATLABandinprogramming,andareallprerequisitesfortherestofthebook.
After that, many chapters in the problem-solving section can be introduced
whendesired,toproduceacustomizedflowoftopicsinthebook.Thisistrue
to an extent, although the order of the chapters has been chosen carefully to
ensure thatthe coverage is systematic.
Theindividualchaptersaredescribedhere,aswellaswhichtopicsarerequired
foreachchapter.PartI,IntroductiontoProgrammingUsingMATLAB,includes
the following chapters.
Chapter 1:Introduction to MATLAB coversexpressions, operators,char-
acters,variables,andassignmentstatements.Scalars,vectors,andmatrices
are all introducedas are manybuilt-in functions that manipulate them.
Chapter2:IntroductiontoMATLABProgrammingintroducestheideaof
algorithms and scripts.Thisincludes simple input and output,and com-
menting.Scriptsarethenusedtocreateandcustomizesimpleplots,andto
dofileinputandoutput.Finally,theconceptofauser-definedfunctionis
introducedwithonly the type offunction thatcalculatesand returnsa
singlevalue.
Preface xv
Chapter3: Selection Statementsintroducesrelational expressions and
theiruseinifstatements,withelseandelseifclauses.Theswitchstatement
is also demonstrated, as isthe concept ofchoosingfromamenu.Also,
functions thatreturn logical true or false are introduced.
Chapter4:LoopStatementsintroducestheconceptsofcounted(for)and
conditional loops (while).Many common uses, such as summingand
counting,are covered. Nested loops are also introduced. Some more so-
phisticatedusesofloops,suchaserror-checkingandcombiningloopsand
selectionstatements, are also covered.
Chapter5: VectorizedCode introduces the idea of“vectorizing” code,
whichessentiallymeansrewritingcodethatusesloopstomoreefficiently
makeuseofbuilt-infunctions,andthefactthatoperationscanbedoneon
vectors and matrices inMATLAB. Functions thatare useful invectorizing
codeareemphasizedinthischapter.Functionsthattimethespeedofcode
are also introduced.
Knowledge of the concepts presented in the first five chapters is assumed
throughout the restof the book.
Chapter6: MATLAB Programs covers more on scripts and user-defined
functions.User-definedfunctionsthatreturnmorethanonevalueandalso
thatdo not return anything are introduced. The conceptof aprogram in
MATLAB, which consists ofa script that callsuser-defined functions, is
demonstratedwithexamples.Alongermenu-drivenprogramisshownasa
reference, but could be omitted. Subfunctionsand scope of variables are
also introduced, as are some debugging techniques.
Thisprogram conceptis usedthroughoutthe rest of the book.
Chapter7:StringManipulationcoversmanybuilt-instringmanipulation
functions as well as converting between string and numbertypes. Several
examplesinclude using custom strings inplotlabelsand inputprompts.
Chapter8: Data Structures:Cell Arrays and Structures introduces two
maindatastructures:cellarraysandstructures.Oncestructuresarecovered,
morecomplicateddatastructures,suchasnestedstructuresandvectorsof
structures,arealsointroduced.Cellarraysareusedinseveralapplicationsin
laterchapters,suchasfileinputinChapter9,variablenumberoffunction
argumentsinChapter10,andplotlabelsinChapter11,andaretherefore
considered importantand are covered first. The restof the chapteron
structures canbe omitted.
Chapter9:AdvancedFileInputandOutputcoverslower-levelfileinput/
outputstatementsthatrequireopeningandclosingthefile.Functionsthat
canreadtheentirefileatonceaswellasthosethatrequirereadingoneline
atatimeareintroduced,andexamplesthatdemonstratethedifferencesin
theiruseareshown.Additionally,readingfromandwritingtospreadsheet