ENGG1801 Matlab Study Notes PDF

Preview

Summary

all notes...

Description

ENGG1801‐MATLABStudyNotes Week4:MATLABBasics,selectionstatementsandArrays  a) MATLABBasics  Commandwindowisgoodforquickcalculationsandtoexperimentideas,butyourworkisgone whenyouexittheMATLABprogram.  WriteaMATLABscripttosaveyourcodesinaM‐file.Thisfilecanbeexecutedonanothercomputer thathasMATLABinstalled.  Workspacewindowliststhenamesandvaluesofyourlocalvariables.  Writecommentsinyourcodestoexplainyourcodestoanotherprogrammerwhoisreadingyour file.  MATLABcontainsmanyin‐builtfunctionsthatyouusebygivingtherightinputdatae.g.sqrt(x).  Typehelp inthecommandwindowforinformationonhowtousethe function.Ex:help sqrt  AMATLABprogramexecutessequentially–codes/commandatLine1,codes/commandatLine2, codes/commandatLine3etc. MATLAB %  clc  clear  ; =

Description Percentsignindicatesacomment.CommentsarenotexecutedbyMATLAB. Clearsthecommandwindow Clearstheworkspace Semi‐colon.Suppressesoutputfromdisplayinginthecommandwindow. Assignmentoperator.Assignsavaluetoamemorylocation,notthesameasequality. Righthand‐side(RHS)isthevalue.Left‐hand‐sideisthememorylocation/variable name.Ex:age = 5. Calculatesthesquarerootofx. DefaultvariablenameforresultsofMATLABcalculations.

sqrt(x) ans  b) Selectionstatements  Selection statements allows the programmer to execute one command (or a set of commands) dependingontheconditions.  Conditionscontainbothrelationalandlogicaloperators.Returnsalogicaldatatypeafterevaluation.  Relationaloperatorscomparevalues. Relational Operators

= == ~=

Morethanorequalto Equalto Notequalto        

Description



Logicaloperatorsareusedtocombinecomparisonstatements.

LogicalOperators && || ~

Description AND.ReturnsTRUEonlyifALLstatementsareTRUE.Otherwisereturns FALSE. OR.ReturnsFALSEonlyifALLstatementsareFALSE.Otherwisereturns TRUE. NOT.~TRUE=FALSE.~FALSE=TRUE.

 Threetypesofselectionstatements: o ifstatement‐performsanactioniftheconditionistrueelseskiptheactionifconditionis false. o if…else statement‐performsanactioniftheconditionistrueelseperformsadifferent actioniftheconditionisfalse. o elseif statement‐performsanactioniftheconditionsaretrueelsechecksanother conditionifitistrue.  Cannestanynumberofifstatementsbuteachifstatementmusthaveanendkeyword.  c) Arrays  One‐dimensionalarrayiscalledavector.  Vectorscanbecreatedby: o Enteringthevaluesdirectly.Ex:a = [1 3 5 7 9] o Enteringthevaluesasarangeofnumbers.Ex:a = 1:2:9 o Usinglinspacefunctiontocreateafixnumberofelementsinthevectorbetweentwo values.Ex:a = linspace(1,9,5)  Determinelengthofavectorusingthefunctionlength(a)wherea isavector. Function length() actuallyreturnsthemaximumdimensionofanarray.   a(k) ‐Accesselementatindex‐kinvectora.  a(end)‐Accessthelastelementinvectora.  Two‐dimensionalarraysmusthavethesamenumberofcolumnsforeachrowandsamenumberof rowsforeachcolumn.Ex: A=[1,2,3;4,5] %Error.Firstrowhasthreecolumns,secondrowhas2columns B=[1,2,3;4,5,6] %Initializesa2x3array.  Determinethenumberofrowsandcolumnsinatwo‐dimensionalarrayusingthefunction size(a). Ex:[r, c] = size(a)  isempty(a)–Returnstrueifarraya isanemptyarrayelsereturnsfalse.                

 Week5:RepetitionStatements(Loops)    

Allowsagroupofstatementstobeexecutedmultipletimes. Numberoftimesaloopisexecuteddependsonthecounterortheevaluationofalogicalcondition. Twodifferenttypesofloops:forloopandthewhileloop. forloop: o Syntax: for i = array %i must be a variable, array usually a vector %body of loop %commands to execute end %i changes to the next element in array o Onceaforloopiscompleted,variableimaintainsthelastvalue.



o Useforloopwhenyouknowhowmanytimestorepeattheloop. o Commonlyusedtoaccesselementsinanarray. whileloop: o Syntax: %initialize variable (counter) to control the loop. count = 1 %count condition to terminate/stop loop while count...