chapter 1matlab programming for engineerszyn.ppt

matlabprogrammingforengineers room414 ee ac sysu emails ynzhang ieee org zhynong yunongzhang 张雨浓 whatismatlab whydowelearnmatlab howdowelearnmatlab introduction whathaveyoulearnedfrommatlab abriefhistoryofmatlab engineeringandscientificapplicationsinvolvealotof numbercrunching formanyyears themainlanguageforthiswasfortran first highlevel programminglanguage andespeciallydesignedfornumericalcomputing here safortrancodetosolveax2 bx c 0 csolveaquadraticequation thisisacomment desc b b 4 a cif desc lt 0 0 goto10desc sqrt desc x1 b desc 2 0 a x2 b desc 2 0 a write 6 solutionsare x1 and x2return10write 6 equationhascomplexroots return problemsusingfortran numbercrunching onacomputercanbetricky problemsthatoccurare lossofprecisionandinaccurateresults x 0 1y 1 0 10 xy should equal0 butprobablydoesnot underflowandoverflow x 1 0e20 x x toobig efficientcodingofalgorithmsnotalwaysobviousdo10n 1 10000010y n sqrt 2 0 x n lessefficient cf inefficientprogrammingerrors solvingalinearsysteminfortran here safortrancodetosolvealinearsystemb a x solveforx itdoesn tcheckfordegeneracyorzeros csolveb a xforx cnisdimensionofvectorsandmatrixcdoesnotuserowinterchange scaling subroutinelinsys n a x b tmp integerndoubleprecisiona n n x n b n doubleprecisiontmp n ratioc forwardeliminationdo13j 1 n 1do12i j 1 nratio a i j a j j a i a i ratio row j do11k j 1 n11a i k a i k ratio a j k a i j 0 0x i x i ratio x j 12continue11continuecontinued c backwardssubstitutionx n x n a n n do21i n 1 1 1tmp x i do20j i 1 n20tmp tmp a i j x j x i tmp a i i 21continuereturnend thisisjustasmallexample afullprogrammaybethousandsoflineslong needfornumericallibraries theu s governmentrecognizedtheseproblems andtheinefficiencyofmanyengineersallwritingthesamealgorithms againandagain so theycommissionednumericalanalyststowritegoodqualityalgorithmsforcommontasks maketheresultsfreelyavailableas libraries ofsubroutinesthananyonecanuseintheirprograms librariesareavailableat lib org examplesofnumericallibraries blas basiclinearalgebrasubroutines operationsonvectors likeaddingtovectors dotproduct norm linpack linearalgebrasubroutinesforvector matrixoperations solvinglinearsystems factoringamatrix invertingamatrix laterreplacedbylapack eispack computeeigenvaluesandeigenvectorsofmatrices example solvea x businglinpack c factortheamatrixcallsgefa a n n ipvt info c copybvectorintoxvectorcallscopy n b 1 x 1 c solvethesystemofequationscallsgesl a n n ipvt x 0 stillnoteasyenough clevemoler mathematician c s professor andco authoroflinpack thoughtthisisstilltoomuchwork writefortran compile debug compile run hewantedtogivestudentseasyaccesstolinpack so hewrotematlab matrixlaboratory interactiveeasyinput easyoutputoperationsonawholevectorormatrixatonceexample solveb a xinmatlab x a b when immediatepopularity matlabquicklybecamequitepopularandusedforbothteachingandresearch itwasalsofree anengineer jacklittle sawmatlabduringalecturebyclevemoleratstanforduniversity hesawthecommercialpotentialand withpermission rewrotematlabincadded m files storedprograms addedmanynewfeaturesandlibrariesfoundedthemathworkstomarketit when softwareprinciples matlabillustratessomeusefuldesignconceptsforsoftware fortran c javacompiler linearalgebralibraries matlab matlab toolkits matlab m files standardbaseplatform modular reusablesoftwarecomponents extensibleusing toolkits oruser contributedprogramscalledm files interactiveuserinterface hidesboringdetails matlabtoday millionsofusers astandardtoolinbothprofessionalandacademicuse toolboxes providingfunctionsformanyapplications controlsystemsidentificationneuralnetworksbio informaticsstatisticsandtime seriesanalysiscandosymbolicmathematics too simulink guibasedsimulationtool matrixlaboratoryhigh performancelanguagefortechnicalcomputingcomputation visualization andprogramminginaneasy to useenvironment summary university levelcomputer programminglanguage cf java c fortran vb andmachine levelcpa typicalapplications mathandcomputationalgorithmdevelopmentmodelling simulation andprototypingdataanalysis exploration andvisualizationscientificandengineeringgraphicsapplicationdevelopment includinggraphicaluserinterfacebuilding applications example1 applications example1 cont solutionofode x 3 y x y xz 26 5x yz xy z butterflyeffect ode45functioninmatlab applications example2 applications example2 cont loadinganimage a imread picture jpg imshow a applications example2 cont showredplane a 2 3 0 imshow a loadinganimage a imread picture jpg imshow a applications example2 cont showgreenplane a 13 0 imshow a applications example2 cont showblueplane a 1 2 0 imshow a why dataanalysis applications example3 stockmarket predictedbyneuralnetworktoolboxinmatlabbp rbfneuralnetworktrainingthenetwork trainfunction applications example3 cont predictingexample applications example3 cont de noiseexample applications example3 cont advantagesofmatlab easetouseinterpretedlanguage likebasic integrateddevelopmentenvironment onlinedocumentation manuals anddemos etc platformindependenceindependenceofoperationsystemsandcomputers windows95 98 me nt 2000 xp unix linux andsuper computers predefinedfunctionsextensivelibraryofpredefinedfunctions suchasarithmeticmean standarddeviation median etc toolboxessuchascommunications controlsystems signalprocessing graphicaluserinterfaceinteractive easiertouseforinexperiencedusers advantagesofmatlab cont howtodefine slowforsomekindsofprocessesinterpretedlanguagenotdesignedforlarge scalesystemdevelopmenthighcostexpensiveforindividuals disadvantagesofmatlab matlabenvironment matlabdesktopincludesthefollowingwindows thecommandwindow thecommandhistorywindow launchpad workspace currentdirectory matlabenvironment cont thecommandwindow allowuserstoentercommandsat underthecommandpromptmatlabcalculatestheansweroncetheenterkeyispressedellipsis isusedifastatementistoolong x1 1 1 2 1 3 1 4 1 5 1 6 x1 1 1 2 1 3 1 4 1 5 1 6 cf ellipse thecommandhistorywindow displayalistofthecommandstypedbeforere executeacommandbydouble clickingitdeleteacommandbyrightclickingitandselectingtheitem deletesection fromthepopupmenu whatif thelaunchpad atreeofdocumentation demos andrelatedtoolsinstalledhere theworkspace computermemoryoccupiedbyvariablesandarraysusedbymatlabwhoslistvariablesandarraysinthecurrentworkspace theedit debugandfigurewindows anedit debugwindowisusedtocreateanew mfileortomodifyanexistingone clicktoolbaricontocreateanewoneclicktoolbaricontomodifyanexistingone afigurewindowisusedtodisplaymatlabgraphics importantcommands demo torunmatlab sbuilt indemonstrationsclc toclearthecontentsofthecommandwindowclf toclearthecontentsofthecurrentfigurewindowclear toclearthevariablesintheworkspace c ctrl c abortcommand toexecutecommandsofcomputer soperatingsystemdiary tocopyallinputandoutputdisplayedinthecommandwindowdiaryoff tosuspendinputintothediaryfilediaryon toresumeinputagain copyjzsf mjzsftest m searchingandlocatingfiles 1 itlooksforthenameasavariable ifitisavariable matlabdisplaysthecurrentcontentsofthevariable 2 itcheckstoseeifthenameisabuilt infunctionorcommand ifitis matlabexecutesthatfunctionorcommand 3 itcheckstoseeifthenameisanm fileinthecurrentdirectory ifitis matlabexecutesthatfunctionorcommand 4 itcheckstoseeifthenameisanm fileinanydirectoryinthesearchpath ifitis matlabexecutesthatfunctionorcommand searchingandlocatingfiles cont rememberinmindneveruseavariablewiththesamenameasamatlabfunctionorcommand otherwise thatfunctionorcommandwillbecomeinaccessible nevercreateanm filewiththesamenameasamatlabfunctionorcommand sin 5 sin 1 answer 5wrong whichtofindoutwhichversionofthefile andwhereitislocated searchingandlo