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ELEMENTSOFNUMERICAL MATHEMATICALECONOMICS

WITHEXCEL

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ELEMENTSOF NUMERICAL MATHEMATICAL ECONOMICSWITH EXCEL

STATICANDDYNAMIC OPTIMIZATION

AcademicPressisanimprintofElsevier 125LondonWall,LondonEC2Y5AS,UnitedKingdom

525BStreet,Suite1650,SanDiego,CA92101,UnitedStates

50HampshireStreet,5thFloor,Cambridge,MA02139,UnitedStates TheBoulevard,LangfordLane,Kidlington,OxfordOX51GB,UnitedKingdom

Copyright © 2020ElsevierInc.Allrightsreserved.

Nopartofthispublicationmaybereproducedortransmittedinanyformorbyanymeans,electronicor mechanical,includingphotocopying,recording,oranyinformationstorageandretrievalsystem,without permissioninwritingfromthepublisher.Detailsonhowtoseekpermission,furtherinformationaboutthe Publisher’spermissionspoliciesandourarrangementswithorganizationssuchastheCopyrightClearance CenterandtheCopyrightLicensingAgency,canbefoundatourwebsite: www.elsevier.com/permissions.

ThisbookandtheindividualcontributionscontainedinitareprotectedundercopyrightbythePublisher (otherthanasmaybenotedherein).

Notices

Knowledgeandbestpracticeinthis fieldareconstantlychanging.Asnewresearchandexperiencebroaden ourunderstanding,changesinresearchmethods,professionalpractices,ormedicaltreatmentmaybecome necessary.

Practitionersandresearchersmustalwaysrelyontheirownexperienceandknowledgeinevaluatingandusinganyinformation,methods,compounds,orexperimentsdescribedherein.Inusingsuchinformationor methodstheyshouldbemindfuloftheirownsafetyandthesafetyofothers,includingpartiesforwhom theyhaveaprofessionalresponsibility.

Tothefullestextentofthelaw,neitherthePublishernortheauthors,contributors,oreditors,assumeanyliabilityforanyinjuryand/ordamagetopersonsorpropertyasamatterofproductsliability,negligenceor otherwise,orfromanyuseoroperationofanymethods,products,instructions,orideascontainedinthe materialherein.

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I

Excelandfundamentalmathematics foreconomics

1.ExcelVBA,solver,andotheradvanced worksheettools

1.1VBAintroductionandmainstatements3

1.2TheExcelSolver:simplexLP,Generalized ReducedGradient,andevolutionary21

1.3What-ifanalysis:scenariomanager,GoalSeek, DataTable,andcontourlines29

1.4Scatterchartsandtrendlines40

2.Univariateandmultivariatecalculus

2.1Numericalmethodsforunivariate differentiation45

2.2Numericalmethodsforunivariate integration58

2.3Numericalpartialdifferentiation66

2.4Applicationsineconomics75 Exercises83

3.Elementsoflinearalgebra

3.1Built-inExcelmatrixfunctionsandbasic operations88

3.2LinearsystemsandresolutionmethodsinExcel: Cramer,Solver,Inverse95

3.3Eigenvaluesandeigenvectorssearch:analytical andgraphicalapproach107

3.4Quadraticformsanddefi nitenessofasymmetric matrix115

3.5Leontiefopenmodel121

3.6Equilibriuminnmarkets124

3.7Economicpolicymodeling:objectivesand instruments129 Exercises134

4.Mathematicsfordynamiceconomic models

4.1Ordinarydifferentialequationsandnumerical methods:EulerandRunge-Kutta140

4.2Forceofinterest,Walrasianstability,utility functions,andcapitalformationwithordinary differentialequation147

4.3Differenceequationsandphasediagrams159

4.4Cobwebmodelofpriceadjustmentandother economicmodelswithdifference equations170

4.5Systemsoflineardifferentialequations181

4.6Tourism fightbetweentwocompeting regions202

4.7Walrasianadjustmentwithentry206 Exercises209

II

Staticoptimization

5.Classicalstaticnonlinearoptimization theory

5.1Classicalunconstrainedoptimizationofa univariatefunction220

5.2Classicalunconstrainedoptimizationofa multivariatefunction232

5.3Someeconomicapplicationsofthenonlinear unconstrainedoptimization247

5.4Numericalsteepestdescentmethodappliedto theunconstrainedoptimization withVBA256

5.5NonlinearproblemsinRn withequality constraints:Lagrangemultipliersand Solver264

5.6NonlinearproblemsinR2 withequality constraints:contourlines272

5.7Nonlinearproblemswithinequality constraints285

Exercises288

6.Microeconomictheoryinastatic environment

6.1Theconsumerproblem:cardinalversusordinal utilityapproach296

6.2Consumeroptimizationandderivationof thedemandcurveinthecardinal approach297

6.3Consumeroptimizationandderivationofthe demandcurveintheordinalapproach307

6.4The firmproblem319

6.5One-inputclassicalproductionfunction320

6.6Two-inputsproductionfunctions322

6.7Isoquantsandtheconstrainedproduction optimizationwithtwoinputs331

6.8ProductionEdgeworthbox,contract curve,andthepossibilityfrontier construction335

6.9Short-run,long-runcostsandtheenvelope averagetotalcostsderivation340

6.10Perfectcompetitivemarkets:short-run,long-run supplycurvesandmarketequilibrium350

6.11Monopolisticmarketequilibrium:the Chamberlinmodel356

6.12Marketswithhigh-entrybarriers:monopolyand theCournotduopolymodel360

6.13Gametheory.Zero-sumgamesand minimaxcriterion:matrixandgraphical resolutions370

Exercises376

7.Linearprogramming

7.1Standardformulationofalinearprogramand resolutionmethods383

7.2Applicationstothestaticproductionplanning andcapitalbudgeting389 Exercises408

8.Nonlinearoptimizationappliedtothe portfoliotheory

8.1Portfoliomodelingandtheefficientfrontier construction417

8.2Investor’sutilityandtheoptimalportfolio choice427 Exercises432

Dynamicoptimization

9.Calculusofvariations

9.1ThefundamentalproblemoftheCalculusof Variations438

9.2DiscreteapproximateCalculusofVariations: Lagrangemultipliersandcontourlines solutions442

9.3SetupoftheExcelworksheetforCalculusof Variationsproblems:theSolversolution451

9.4GeneralcasesdevelopedinExcelwith fixedand variableterminalpoints453

9.5Dynamicoptimizationforamonopolist469

9.6Unemploymentandinflation471

9.7TheEisner Strotzmodel475

9.8TheoptimalconsumptionRamseymodel479

9.9Inventorydynamicoptimization481

9.10Optimalcapitalstructureandthe firmcostof capital482

9.11ContourlinessolutionforCalculusofVariations usingtheVBAcode487

9.12CalculusofVariationswithfunctionals involvingtwoindependent functions494

9.13CalculusofVariationsconstrainedproblems497

9.14CheckingtheSecond-OrderConditionsin Excel505 Exercises511

10.Theoryofoptimalcontrol

10.1Theoptimalcontrolproblemandthe Pontryagin’smaximumprinciple522

10.2NonlinearHamiltonianandlinearHamiltonian (bang-bangcontrol)523

10.3SetupoftheExcelworksheetforoptimal controlproblems525

10.4Bang-bangcontrolproblems542

10.5Consumptionmodel547

10.6Investmentmodel554

10.7Inventoryoptimization561

10.8Twostatevariablescontrol problems563

10.9Current-valueHamiltonian571

10.10Constraintsonthestatevariable:alinearcase withaninventoryapplicationwithVBA576

10.11Steepestdescentnumericalapproachfor optimalcontrolproblemsusingVBA587

10.12Checkingthesufficientconditionsin Excel593

Exercises600

11.Discretedynamicprogramming

11.1Bellman’sprinciple,discreteshortestpath problems,andtheExcelMINIFS function612

11.2Discretedynamicsystems:tabularmethod, Exceldatatable,andSolver619

11.3Cargoloadingallocationproblems:tabular methodandtheExcelSolver629

11.4MultistageallocationproblemsusingtheExcel Solver632

11.5Equalityconstrainedoptimizationproblems usingtherecursiveBellman’sapproach636

11.6Dynamiceconomicproblemssolvedwith DiscreteDynamicProgramming639

11.7DiscreteDynamicProgramming,Optimal Controltheory,andCalculusofVariations:a synthesis649

Exercises652

IV Specialtopics

12.Dynamicproductionplanningand inventorymodeling

12.1Multiperiodproductionmodelswithlinear programming661

12.2Wagner Whitinalgorithmforinventory dynamicmodeling669

12.3EliezerNaddorstochasticsingle-period inventorymodels677 Exercises687

13.Dataanalysisforbusinessand economics

13.1Asimplewaytoorganizeaspreadsheetusing theVBAcodeandbookmarks696

13.2Pivottables,Pivotcharts,anddynamic dashboardsformanagerialdataanalysis697

13.3Basicdescriptivestatistics711

13.4Somenumericalcalculusappliedtocontinuous densities721

13.5Univariate,multivariateregressionanalysisand theANOVAtables727

Exercises756

14.EssentialMonteCarloanalysis

14.1TheMonteCarlomethodandthegeneration ofrandomnumbers764

14.2TheMonteCarlomethodforbusiness decisions773

14.3Numericalintegration788 Exercises792

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Excelandfundamental mathematicsforeconomics

PartIofthisbookaimsatgivingtothereaderthefundamentaltoolsof someimportantadvancedworksheetcapabilities,includingtheExcelVBA, aswellasthefundamentaltoolsofthemathematicaleconomicsapplied withinaspreadsheet.Thesearealltoolsthatwillbeneededwithinthe courseofthewholebookandtoolsthatanyeconomistanalystshouldmaster withinacomputerlanguageframework.

Chapter1willreviewsomeVBAcodes,whosepriorknowledgewouldbe somehowrequiredfromthereader,inordertooptimallyutilizetheworksheetsthatwillbeimplementedwithinthebook.TheExcelmacrosused withinthebookarenotataveryadvancedlevel,butstill,theywillrequire (besidethemathematicalknowledge)acertaindegreeofVBAprogramming languagemastery.

Otheradvancedfeatures,liketheExcelSolver,the what-ifdatatableanalysis (thesetwowillbeusedalotinthebook), contourdiagrams, scattercharts,and trendlines willbeintroducedandthendevelopedindetailwithinthebook.

Chapters2 4willinsteadgivetheessentialelementsofthemathematical economicsappliedwithExcel.

Threeimportantareasofthemathematicaleconomicsarecoveredhere.

Chapter2willcovertheessentialelementsofthestandardcalculus (numericaldifferentiationandintegration)appliedwithinaspreadsheet.

Chapter3isdedicatedtotheessentialelementsofthelinearalgebra.

Chapter4isinsteaddevotedtothedynamicalmathematics(ordinary differentialanddifferenceequations,aswellasthesystemsofdifferential equations).Thisisachapterofparamountimportanceasmanyofthetechniqueswewilldevelopinthischapterwillbeusedwithinthedynamicoptimizationsectionandalsobecausethedifferentialanddifferenceequations representthekeyconstituentareaoftheeconomicdynamicmodeling.

Inallthesethreechapters,someeconomicapplicationsarealsoproposed.

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1 ExcelVBA,solver,andother advancedworksheettools

OUTLINE

1.1VBAintroductionandmain statements3

TheVBAEditorandthemodules3 1VisualBasicMacros6 UsingtheMacroRecorder9 MainVBAstatementsusedwithinthe book(theloopingstructures)10

EXAMPLE 1(CONSTRAINEDOPTIMIZATION IN <2 WITH LAGRANGEMULTIPLIERS USINGTHE VBA DO UNTIL)13 ForNextLooping16

EXAMPLE 2(HEATSHEETHIGHLIGHTING THEBESTPERFORMINGFUNDSWITHIN THEIRPEERGROUP)17

2UserDefinedFunctions(orfunction procedures)19

EXAMPLE 3(NUMERICAL INTEGRATION)19

1.2TheExcelSolver:simplexLP, GeneralizedReducedGradient,and evolutionary21 NonlinearGeneralizedReduced Gradient21 SimplexLinearProgramming26 Evolutionary27

1.3What-ifanalysis:scenariomanager, GoalSeek,DataTable,and contourlines29 EXAMPLE 1(WHAT-IFANALYSISON NPV AND IRR CALCULATION)31

1.4Scatterchartsandtrendlines40 .

1.1VBAintroductionandmainstatements

TheVBAEditorandthemodules

WhenwritingaVBAcode,the VBEditor needstobeusedinExcel.TheVBEditoristhe workingareawherewewillwritea Macro anditisaccessiblefromthetabDeveloperofthe Ribbonbar,asshownin Fig.1.1-1.Then, Fig.1.1-2 willappear.

1.ExcelVBA,solver,andotheradvancedworksheettools

Ontheleft-handsideof Fig.1.1-2,wehavethe ProjectExplorer (atthetop)andasecond panel(atthebottom)whichcontainsthe Properties (modifiablebytheuserwhennecessary) referredtoany ExcelObject weselectinthe VBAProject window:aworksheet,aworkbook, oramoduleitself.

Now,whatwehavetodoistoopentheactualworkingareawheretowriteourVBAcode, andthisisdonebyinsertinga Module,asin Fig.1.1-3

Amodulecanbeinserted,forexample,byclickingonInsertonthe MenuBar andthenselectingModule,and finallytheVBEditorwillbecompletedwiththeModuleinsertedasin Fig.1.14.Ifwewant,wecanrenameaModuleusingthepropertieswindowatthebottomofthescreen of Fig.1.1-4.Whenrenamingit,wejustneedtopayattentiontospaces,whicharenotaccepted, andtheunderscorecharactershouldbeusedinplaceofaspace.Nowthatwehaveamodule,we canbeginwritingacode.Thisiscalleda Macro (orprocedure,orroutine).

ExcelVBAalsoallowstocreatea UserDefinedFunction,whichwillenrichthelibraryof thebuilt-infunctions.

FIGURE1.1-2 VBAProjectExplorer(withExcelObjects)andthePanelPropertiesatthebottom.

FIGURE1.1-1 TheVBEditorintheExcel2019.

FIGURE1.1-3 InsertingaModulefromtheMenubar.

FIGURE1.1-4 ModuleInsertedwheretowriteaVBAprogram.

1.ExcelVBA,solver,andotheradvancedworksheettools

1VisualBasicMacros

InExcel,theroleofaMacroisessentiallythatofgettinganactionautomated,without manualinterventionontheExcelsheet.ItisacommandwegivetoExcel,suchthatitperformssomethingwewanttodo(e.g.,arepeatedcalculationuntilaspecifiedcellisequal tozero).Thewaytodothatistocreatea Sub procedureintheModule.

Theprocedureisinthefollowingform:

VBAStatements

Supposewewanttoincrementthevaluein CellA1ofaworksheetby1.Thecodewouldbe asin Fig.1.1-5.Nowaquestionarises.Howcanwegetthecodeactivatedintheworksheet? Inotherwords,howcanwemakethemacrorun?Thisisnormallydoneinsertinga Button in theworksheet,whichisthenassociatedtothespecificcodewehavecreated.Thebuttonwe arereferringtoisthe FormControl,asshownin Fig.1.1-6

FIGURE1.1-5 IncrementingthevalueofaCell.
FIGURE1.1-6 FormControlButtontorunaSub.

FIGURE1.1-7 InsertingaButton(formControl)inaworksheet.

UsingtheAlt-KeytofacilitatetheButtonpositioningonthesheet,wedecidetoposition theButtonasin Fig.1.1-7

Releasingthemouse,ExcelwillaskustoassociateaMacrotothisButton,andwechoose theonlyMacroavailablesofar,whichisthe SubIncrement Value asin Figs.1.1-8.Then,the

FIGURE1.1-8 AssigningamacrotoaButton.

1.ExcelVBA,solver,andotheradvancedworksheettools

FIGURE1.1-9 NamingtheButtonforthemacro “Increment_Value”

macroisavailabletoberunthroughtheButton “IncrementValue,” asin Fig.1.1-9.Wecan createasecondMacrocalled “Reduce_Value ” asin Fig.1.1-10,insertingasecondButtonasin Fig.1.1-11

FIGURE1.1-10 Secondmacro “Reduce_Value.”

UsingtheMacroRecorder

TheMacrocanbealsorecordedinExcelusingthe RecordMacro optionunderthe DeveloperTab.

Forexample,supposewewanttoaddnew sheetstoaworkbook;wecansimplyrecordamacrotodothat.Whatwedoisjustclickingonthe RecordMacro optionaddinganewsheet;then,whenwe fi nishrecording,weclickonthelittlesquare Stop Recording shownin Fig.1.1-12 .Themacrowillbeavailableinanewmoduleofthe ProjectExplorer.

Recordingamacroisusefulwhenwearenotsureabouttheexactcodetouseandwe lookforsomehintssuggestedbyExcelregardingaspecificoperationwewanttoperform. Wecanrecordasimilaroperation,thenmodifyitobtainingthe finalinstructionwewere lookingfor.

Theresultingmacro(tobefoundintheVBEditor)wouldbeasfollows:

SubAdd New SheetsðÞ

Sheets AddAfter : ¼ ActiveSheet

FIGURE1.1-11 SecondButtonforthemacro “Reduce_Value.”

StopRecording. 1.ExcelVBA,solver,andotheradvancedworksheettools

Ifwewanttoaddfoursheetsinoneshotthemacrowouldbemodifiedasfollows:

SubAdd 4 New SheetsðÞ

Sheets:AddAfter : ¼ ActiveSheet; Count : ¼ 4

EndSub

MainVBAstatementsusedwithinthebook(theloopingstructures)

ManyoftheVBAsubproceduresneedtobeenteredmanuallyintheVBEditor,andwe willshowherethemainstatementsusedwithinthebook.

Thesearethe Looping structures,whichareVBASubsthatare finalizedat:

1. repeatingasetofinstructions,untilaspeci ficgoalisreached,forexample,untilthe Excelsetsaspeci ficcellequaltozero,oruntilaspecifictargetcellislessthanadesired ε (theSteepestDescentVBAcodeshowninSection5.4isanexample)or

2. finalizedatrepeatingasetofinstructionsforacertainnumberoftimes.

A looping structurebelongingtothe firstcategoryisthe DoUntil statement,sometimes usedinconjunctionwiththe ExcelSolver,tooptimizeaspecificobjectivefunction.

Supposewehavealistof10numberslikein Fig.1.1-13,wherethelastoneineffectcontainsaformula.Inthiscase,itisjustaformulathataddsthevalue1tothepreviouscell. Theobjectiveistoaddautomaticallyanewrowinanewupdatingsheetround,including thecountingformulaandremovingtheformulafromthepenultimatecell(whichwasthelast cellinthepreviousupdatinground).

Todothatusingthe DoUntil statementcanbeaperfectsolution.Thefollowingwouldbe thestatementwhichmakesExcelselectthe CellA1asa firststepandthenmoveforwarduntil thecellisempty:

Rangeð}A1}Þ:Select

DoUntil IsEmptyðActiveCellÞ

FIGURE1.1-12

ActiveCell:Offsetð1; 0Þ:Select Loop

Excelmovesforwardfrom CellA1alongthesamecolumnusingtheinstruction:

ActiveCell Offsetð1; 0Þ Select

insertedbetween DoUntil and Loop (thisisalwaysinsertedbelowtheinstructionwewantto repeat).

Thecompletecodeofwhatwewanttoachieveisshownin Fig.1.1-14.Wecanfollowstep bystepthemacrobypressing F8onthekeyboard.Thisisuseful,especiallywhensomething doesnotworkasplannedandwewanttostudythemacroindetail,investigatingatwhich lineofthecodethemistakecouldbelocated.Thiscanbedonealsousingthe Debug option fromtheMenuBarasshownin Fig.1.1-15.

Therearesomeotheralternativestotestforablankcell,notonlyusingthe DoUntil Is Empty(ActiveCell);forexample,wemayalsousethefollowing: DoUntil ActiveCell Value ¼ }}

Also,averyslightlydifferentcodewouldbethe LoopUntil statement,asdescribedas follows

FIGURE1.1-13 Listofnumbersfrom1to10.

1.ExcelVBA,solver,andotheradvancedworksheettools

FIGURE1.1-14 AddinganewRowtoanArray.

FIGURE1.1-15 SteppingthroughaVBAcode.

I.Excelandfundamentalmathematicsforeconomics

ActiveCell:Offsetð1; 0Þ:Select

LoopUntil IsEmptyðActiveCellÞ

wherewehavemovedthe Until,withtheconditiontobemet,after Loop.

Anothersimilarstatement,the DoWhile statement,wouldalsoreachthesamesolution withthecodeexpressedasfollows:

Rangeð}A1}Þ:Select

DoWhile ActiveCell:Value <> }}

ActiveCell:Offsetð1; 0Þ:Select Loop

Inthiscase,wehavereplacedthetestingconditionoftheemptycell,toexittheloop, testingwhetherthecellisdifferentfromzero.

Anotheralternativeistousethe if statementinsidethe Loop asfollows: Do If ActiveCell:Value ¼ }} ThenExit Do

ActiveCell Offsetð1; 0Þ Select Loop

EXAMPLE 1(CONSTRAINEDOPTIMIZATIONIN <2 WITH LAGRANGEMULTIPLIERS USINGTHE VBA DO UNTIL)

LetustrytosetupaVBAcodeusingthe DoUntil Loopingstatement,fortheapproximate solutionofthefollowingconstrainedoptimizationproblem(thesameexampleinsolvedusingtheExcelSolverinSection5.5):

TheLagrangianfunctionis:

1.ExcelVBA,solver,andotheradvancedworksheettools

FIGURE1.1-16 Example1:constrainedoptimizationexcelsetup.

fromwhichweobtainthesystemof(3) first-ordercondition equations:

Fromthethirdequation,weobtain l1 ¼ 5andthestationarypoint x*(4.5,5.5).

Thewaywecansolvetheproblemis firstsettingupinExceltheequations Lðx1 ; x2 ; l1 Þ;

vLðx;lÞ vx1 ,and vLðx;lÞ vx2 asin Fig.1.1-16,where:

CellA2 CellB2 ¼ x1 and x2,respectively,linkedtotheoptimizationresultsof Fig.1.1-17.

CellB3 ¼ ObjectiveFunction

CellB4 ¼ Constraint

CellE1 ¼ LagrangeMultiplier l1

(Itisthisvaluethatwillbeincrementedordecremented via theVBAcodeof Fig.1.1-18, untilthesolutionisfound)

FIGURE1.1-17 TestConditionfortheoptimization.

FIGURE1.1-18 VBALoopingstructureforthenonlinearconstrainedoptimization(withLagrangemultipliers).

SincebeforetheoptimizationwedonotknowwhichsigntheLagrangemultiplierwilltake on,wewilljusttryapositivevalue(thismustallowachangeinthesignofthepartialdifferentialunder ColumnD and ColumnI).

IftheMacrostopswithout findingthesolution,thenwetrywithanegativevalueinthe Lagrangemultiplier(again,thismustallowachangeinthesignofthepartialdifferentialunder ColumnD and ColumnI).

Theworksheetlimitsthechoiceuptoamaximumvalueof3fromaminimumvalue of 10,usingadrop-downlist.

Thesolutionwillbefoundwhen CellN18isequaltozero.See Fig.1.1-17 and Table1.1-1.

ColumnA ¼ ifstatementthatreturnsx1

TABLE1.1-1

ColumnB ¼ x1

ColumnC ¼ Lagrangianasafunctionofx1 holdingx2 constant

ColumnD ¼ partialdifferential vLðx; lÞ vx1

Whenthedifferentialchangessign,thevalueof2isreturned.Atthesamerowthestationarypointwillbefound.

ColumnF ¼ ifstatementthatreturnsx2

ColumnG ¼ x2

ColumnH ¼ Lagrangianasafunctionofx2 holdingx1 constant

ColumnI ¼ partialdifferential vLðx; lÞ vx2

ColumnJ ¼ testconditiononthesignof vLðx; lÞ vx2 :

Whenthedifferentialchangessignthevalueof2isreturned.Atthesamerowthestationarypointwillbefound.

Beginningwithapositivevaluein CellE1ofLagrangemultipliertheVBALoopof Fig.1.118 reducesthisvaluerepeatedly(thisisbecauseoftheVBA DoUntil)by0.5untiltheoptimizationisreached;i.e.,when CellN18 ¼ 0(andconstraint x1 þ x2 ¼ 10issatisfied);when optimizationisreached CellN20s0mustalsoresult,whichmeansthatthetwopartialdifferentialshavechangedsignsomewherealongtherangeoftheindependentvariables.

Otherwise,ifthe CellE1reachesthevalueofzerowithoutanyoptimization(namely, Cell N18isstilldifferentfromzero)theVBAexitstheLoopandreturnsa MessageBox.Therefore, weneedtoreoptimizeinputtingin CellE1anegativevalue,makingthemacroincreasethis valueuntiltheoptimizationisreached.

Table1.1-1 isthe finaloptimizationresult.Inthiscase,theoptimizingLagrangemultiplier turnsouttobenegative(i.e., l1 ¼ 5)ascalculatedbythetheoreticalsolution.

ForNextLooping

Anotherloopingstructureisthe ForNext. InVBA,thisloopingstructurerepeatsasetof instructionsacertainnumberoftimes.

Whatweneedhereisa variable whichallowstocountthroughtheloop.Thisisthe Loop Counter,anditisnormallydenotedwithaletter.

InVBA,itisdefinedasanintegerasfollows:

DimiAsInteger

The ForNext statementthenbegins,recallingthe LoopCounteri andstatinghowmany times(e.g.,100)weneedtorepeatasetofinstructions:

Fori [ 1 to 100 whichmeansthatthe loop willcount100times.

Whatmakestheloopgoforwardistheword Next.Between For and Next wehavethereforetoinsertthesetofinstructionstoberepeated.

EXAMPLE 2(HEATSHEETHIGHLIGHTINGTHEBESTPERFORMINGFUNDSWITHINTHEIR PEERGROUP)

Letusconsideraninvestmenthousethathasgatheredthedataof Table1.1-2 onthefunds theymanage,where:

% Change ¼ performanceoftheperiod ðOneweek ; OneMonth; etc Þ

Rank ¼ RankpositionwithinthePeer Group

Count ¼ NumberofFundswithinthePeer Group

Qrtl ¼ InwhichQuartile ðfrom 1 to 4Þ thefundispositionedwithinthePeer Group

Forexample,Fund1hasaperformanceof 3.79%overamonth,withinitspeergroup (e.g.,EuroEquity)madeof55funds(Count)anditappearstobeinthe firstquartile,as it’sbeenrankedintheeighthposition.

Now,usingtheVBA ForNext statement,wewanttoperformaconditionalformatting changingthecolortotheFundsforeachperformanceperiod(OneWeek,OneMonth,Three

TABLE1.1-2 PerformanceandRankingforeachfundwithineachPeerGroup.

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