Vba & Excel-mvo

7/28/2019 Vba & Excel-mvo

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VBA & Excel.ppt 1

Primer on VBA & Excel for

Discrete-Event Simulation

See also IOE574-startup.xls
http://www.engin.umich.edu/class/ioe574/IOE574-startup.xlshttp://www.engin.umich.edu/class/ioe574/IOE574-startup.xlshttp://www.engin.umich.edu/class/ioe574/IOE574-startup.xlshttp://www.engin.umich.edu/class/ioe574/IOE574-startup.xls


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VBA & Excel.ppt 2

Visual Basic for Applications

VBA a significant subset of the stand-alone Visual Basic programming language

It is integrated into Microsoft Office

applications (and others, like Arena) It is the macro language of Excel

You can add

Forms for dialog boxes with user input Classes for object definitions

Modules containing procedures


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VBA & Excel.ppt 3

VBA & Excel for Discrete-EventSimulation

Advantages VBA is a full-featured programming language

You have access to Excel functions for

computation and Excel for storing andanalyzing outputs including USERINTERACTION!

Disadvantages VBA is interpreted, not compiled, so execution

is slow (can be overcome by compiling VB)

Excel functions can be buggy


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VBA & Excel.ppt 4

Accessing VBA in Excel

Tools Macros Visual Basic Editor

Enter VBA through the navigation buttonsin the top toolbars

VBA DesignMode

Visual BasicEditor

Design mode is the time

during which no code fromthe project is running andevents from Excel or yourproject will not execute.


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VBA & Excel.ppt 5

VB Edit Window

Project

Explorer

PropertyInspector

Code Window


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VBA & Excel.ppt 6

Structure of VBA Project

Modules are collections of VBA code

Procedures (Subroutines - Subs) andFunctions

Declarations come before any Subs orFunctions that are global to the Module

UserForms are graphic objects for user

input and output; we will not have to workwith UserForms


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VBA & Excel.ppt 7

Variables

Declare byDim varname As Type

Better to use Data Types:Dim amount AsDouble note double precision is useful for us!

Dim yearAsIntegerDim name AsString

Other data types: Boolean, Byte, Currency,Date

Default (no type) is Variant Option Explicit forces all variables to be

declared


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VBA & Excel.ppt 8

Variables(contd.)

Can declare type by appending a symbol:% - integer & - long integer! - single # - double@ currency $ - string

Can modify scope (outside Subs & Fcns)

Private L AsInteger(only current module)

Public billsPaid AsCurrency(available to any module)


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VBA & Excel.ppt 9

Constants & Statics

[Public|Private] Const constantName [Astype] = expression Value cannot be changed

PublicConst PI = 3.1, NumPLANETS = 9 Oops, make that 8 as of August 2006!

Static causes variables in Subs and

Functions to retain their values (normallylost when you exit Sub or Function) Static yourName AsString


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VBA & Excel.ppt 10

Arrays

Dim vect(1 to 100) as IntegerDim Elf(0 to 5, 0 to 20) as String

You can also dynamically allocate andreallocate an array

Dim Calendar() as Integer

ReDim Calendar (1 to 31) as Integer


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VBA & Excel.ppt 11

Control Structures

Decisions

IfanyDate < Now Then

anyDate = NowEndIf

Next, consider If Then Else


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VBA & Excel.ppt 12

Decisions(contd.)

IfIndex = 0 ThenX = X + 1Y = VBA.Sqr(X)

ElseIfIndex = 1 ThenY = VBA.Sqr(X)

ElseIfIndex = 2 ThenY = X

ElseX = 0EndIf


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VBA & Excel.ppt 13

Decisions(contd.)

SelectCase IndexVariable

Case 0

statements

Case 1 to 10

statementsCase Is < 0

statements

CaseNumSteps

statementsCaseElse

statements

EndSelect

Notice that the cases

can be constants, ranges,conditions and variables;this is a powerful controlstructure that we will useto select events to execute


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VBA & Excel.ppt 14

Loops/Iterations

Do {While|Until}conditionstatements

Loop

-------------------------------------------

Do statementsLoop {While|Until}condition


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VBA & Excel.ppt 15

Loops(contd.)

Forcounter = start To end [Step increment]statements

Next counter

--------------------------------

ForEach element In groupstatements

Next element


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VBA & Excel.ppt 16

Exiting Control Structures

ForJ = 1 To 10 Step 2[statement block]ExitFor[statement block]

Next J-----------------------Do

[statement block]ExitDo[statement block]

Loop Until Check = False

Optional statements to

allow early exit from theloop before thetermination condition


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VBA & Excel.ppt 17

Exit Command Details

Exit Do Provides a way to exit a Do...Loop statement. It can be used onlyinside a Do...Loop statement. Exit Do transfers control to the statementfollowing the Loop statement. When used within nested Do...Loopstatements, Exit Do transfers control to the loop that is one nested levelabove the loop where ExitDo occurs.

Exit ForProvides a way to exit a Forloop. It can be used only in a For...NextorForEach...Next loop. Exit Fortransfers control to the statementfollowing the Next statement. When used within nested Forloops, Exit Fortransfers control to the loop that is one nested level above the loop whereExit Foroccurs.

Exit Function Immediately exits the Functionprocedure in which it

appears. Execution continues with the statement following the statementthat called the Function.

Exit Sub Immediately exits the Sub procedure in which it appears.Execution continues with the statement following the statement that calledthe Sub procedure.
http://hhobj_4.click%28%29/http://hhobj_5.click%28%29/http://hhobj_5.click%28%29/http://hhobj_4.click%28%29/


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VBA & Excel.ppt 18

Code Modules

Excel Objects (ThisWorkbook, Sheet#)

Modules

Typically we put our code here

A Module is a collection of Subs andFunctions

Insert Module

More: Class Modules (see master used for simlib)

User Forms


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VBA & Excel.ppt 19

Procedures

Sub name(arguments) (i.e., subroutine) no value returned in the sense of a function, but

variables are modified.

Called as needed via

Call mySub(param1, param2)

Function name(arguments) AS type (i.e., function)

value returned assign return value to function name: e.g.,

X = myFunction(2, 7, Z)


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VBA & Excel.ppt 20

Subs can also have Public or Private scope(default is Public)Public Sub MM1_main() this is a common way to begin

a sub that is public and all variables to becommunicated to the routine calling it are public.

Basic syntax{Public|Private} Sub name(arguments)

[statements]

Exit Sub[statements]End Sub

Subs

Optional way to leave the Subbefore reaching the End statement


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VBA & Excel.ppt 21

Functions

Functions can also have Public or Privatescope (default is Public)Public Function Timer() As String e.g., Timer returned

as Failure

Basic syntax

{Public|Private} Function fname(arguments) AS type[statements]fname = valuExit Function[statements]

End Function Optional way to leave the Functionbefore reaching the End statement

Fname returned to modulewith value valu


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VBA & Excel.ppt 22

Pass by Reference (default) means thatchanges to the value of the variable will bereturned

Sub stuff(item As String, price as Integer)

Pass by Value means only the value is

passed so the original variable is unchanged

Sub stuff(ByVal item As String, ByVal priceas Integer)

Arguments for Procedures


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VBA & Excel.ppt 23

Some Useful Code for Interactingwith Excel

The following are some pieces of codethat are useful for doing VBA with Excel.

See the code on the course web site forother examples.

Basic_Simulation_Modeling.xls

IOE574-startup.xls

others yet to come.
http://www.engin.umich.edu/class/ioe574/r/Basic_Simulation_Modeling.xlshttp://www.engin.umich.edu/class/ioe574/IOE574-startup.xlshttp://www.engin.umich.edu/class/ioe574/IOE574-startup.xlshttp://www.engin.umich.edu/class/ioe574/IOE574-startup.xlshttp://www.engin.umich.edu/class/ioe574/IOE574-startup.xlshttp://www.engin.umich.edu/class/ioe574/r/Basic_Simulation_Modeling.xls


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VBA & Excel.ppt 24

This is how you addressVBA intrinsic functions

Writing to a Sheet

Put the absolute value of the variableFudge in row 2 (or I), column 20 (or J) ofthe Worksheet named mySheet.

Worksheets(mySheet).Cells(2,20) = VBA.Abs(Fudge)

Worksheets(mySheet).Cells(I,J) = VBA.Abs(Fudge)

Worksheets(mySheet).Range(T2)=VBA.Abs(Fudge)

Range is general see next page


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VBA & Excel.ppt 25

Ways to use .Range Method

Range("A1") Cell A1

Range("A1:B5") Cells A1 through B5

Range("C5:D9,G9:H16") A multiple-area selection

Range("A:A") Column A

Range("1:1") Row 1

Range("A:C") Columns A through C

Range("1:5") Rows 1 through 5Range("1:1,3:3,8:8") Rows 1, 3, and 8

Range("A:A,C:C,F:F") Columns A, C, and F


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VBA & Excel.ppt 26

Reading from a Worksheet

To read in a value, use the .Value method,applying the same ideas used for writing:

X = Worksheets(mySheet).Range(T2).Value

note: T = column 20, so T2 is col. 20, row2

Excel likes the (column, row) order ratherthan (row, column) when using Range


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VBA & Excel.ppt 27

Use an Excel Function

VBA has a limited number of built-infunctions, but you can access the plethoraof Excel worksheet functions.

This example uses the Excel Max function

W = WorksheetFunction.Max(0, W + S - a)


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VBA & Excel.ppt 28

Running the Code

Your modules will as appear as Macrosthat can be run from Excel under

Tools Macro Macros dialogue-box Perhaps the easiest way to run the code is

to place your cursor in the module youwant to run and press theRun Sub/UserForm button. (there is agreen play button on the toolbar, too)


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VBA & Excel.ppt 29

DebuggingUseful tools in theDebug menu

Setting break pointscauses code to stopwhen the point is reached(F5 to continue)

Passing the cursor

over variablesshows their currentvalue


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VBA & Excel.ppt 30

Dim Clock As Double ' simulation clockDim NextFailure As Double ' time of next failure eventDim NextRepair As Double ' time of next repair eventDim S As Double ' system stateDim Tlast As Double ' time of previous eventDim Area As Double ' area under S curve

Public Function Timer() As String

' Determine the next event and advance timeIf NextFailure < NextRepair ThenTimer = "Failure"Clock = NextFailureNextFailure = 1000000

Else

Timer = "Repair"Clock = NextRepairNextRepair = 1000000

End IfEnd Function

These variablesare global since

they are declaredbefore any Subor Function

Notice that Function must

be typed

Value "Failure" is returnedas Timer, the name of the

function.

An apostrophe indicates a commentDiscrete TTF EXAMPLE


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VBA & Excel.ppt 31

Public Sub MainProgram()' Program to generate a sample path for the reliability example

Dim NextEvent As String

S = 2Clock = 0Tlast = 0

Area = 0NextFailure = WorksheetFunction.Floor(6 * Rnd(), 1) + 1NextRepair = 1000000

Do Until S = 0NextEvent = TimerSelect Case NextEventCase "Failure"

Call FailureCase "Repair"

Call RepairEnd Select

LoopMsgBox ("System failure at time " _

& Clock & " with average # components " & Area / Clock)End Sub

NextEvent is local to this Sub since itis declared within the Sub

Note use of an Excel function

A Do Until loop and a Select Casestatement


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VBA & Excel.ppt 32

Public Sub Failure()'Failure event

Area = Area + (Clock - Tlast) * STlast = Clock

S = S - 1If S = 1 ThenNextFailure = Clock +

WorksheetFunction.Floor(6 * Rnd(), 1) + 1

NextRepair = Clock + 2.5End If

End Sub

P bli S b R i ()


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VBA & Excel.ppt 33

Public Sub Repair()'Repair event

Area = Area + (Clock - Tlast) * S

Tlast = Clock

S = S + 1If S = 1 Then

NextRepair = Clock + 2.5NextFailure = Clock +

WorksheetFunction.Floor(6 * Rnd(), 1) + 1End If

End Sub


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VBA & Excel.ppt 34

Finishing Up

Exercise: Write a Sub that inserts aworksheet named Count into the

Workbook, then writes the numbers

1,2,,10 in the first row, the first tencolumns. Use a loop to do this.


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VBA & Excel ppt 35

Finding/Creating a SheetDim found As Boolean

Dim sheetNext As Worksheet' Set up mySheet sheet for output

found = FalseFor Each sheetNext In Worksheets

If sheetNext.Name = mySheet" Then

found = TrueExit ForEnd If

Next sheetNext

If found = True ThenWorksheets(mySheet").Select

ActiveSheet.UsedRange.ClearElse

Worksheets.AddActiveSheet.Name = mySheet"

End If

FYIuseful sol. To exercise

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Vba & Excel-mvo