Modeling using VBA

Covered materials

- Userforms- Controls- Module- Procedures & Functions- Variables- Scope

Variant “Data Type”

• In VB you don’t have to declare variable before its usage– Then, VB will by itself declare such variable as “Variant”

• You can also declare variable as “Variant”– Dim myVar as Variant

• Variant – means that the variable may contain any data type

Variables Assignment

• To assign a value to a Numeric or String type Variable, you simply use your Variable name, followed by the equals sign (=) and then the String or Numeric

• To assign an Object to an Object type variable you must use the key word "Set"

Variables Assignment – cont.Sub ParseValue()

Dim varName as String varName = “Cuong Do”

Dim varAge as Integer varAge = “28”

Dim varCell as Range Set varCell = Range("A1")

varCell.Value = “123”End Sub

VBA Variables Scope & LifecycleThe scope & lifecycle of a variable defines the code where the variable can be accessed and time when the stored data is kept inside the variable

• Procedure-Level– Variables defined inside procedures– Can be accessed only inside the procedure and keep their data until the

End statement of the procedure• Module-Level

– Defined in the top of a Module– Any procedure inside the Module can access the variable– The variable retains the values unless the Workbook closes

• Project-Level, Workbook Level, or Public Module-Level– Defined as “Public” in the top of a Module– Can be accesses by any procedure in any module– The variable retains the values unless the Workbook closes

VBA Variables Scope & Lifecycle – cont.

• Sub scopeExample()Dim x as Integerx = 5

End Sub• Dim y as Integer

‘all the module procedures are here…• Public z as Integer

‘all the module procedures are here…

Procedure level variables

Module level variables

Project level variables

Which variable?Module1

Userform8

How to address public variables?

Userform8

Module1

Basic Excel Classes

• Workbook: the class represents an Excel file• Worksheet: represents a single worksheet• Cell: represents a single cell

Excel Containers

• Workbooks: a collection of objects of class “Workbook”

• Worksheets: a collection of objects of class “Worksheet”

• Range: a range of objects of class Cell

Referring to Cells by Using a Range Object

Sub Random() Dim myRange As Range Set myRange =

Worksheets("Sheet1").Range("A1:D5") myRange.Formula = "=RAND()" myRange.Font.Bold = True

End Sub

Referring to Cells by Using a Range Object

Sub Test1()Range("A10").Value = "123"End Sub

Sub Test2()Set varRange = Range("A10")varRange.Value = "123"End Sub

Sub Test3()Worksheets(1).Range("A10") = "123"End Sub

Sub Test4()Worksheets("Sheet1").Range("A10") = "123"End Sub

Same outcome

here

Referring to Multiple Ranges

Sub ClearRanges() Worksheets("Sheet1")._ Range("C5:D9,G9:H16,B14:D18").ClearContents

End Sub

Referring to Cells by Using Index Numbers

• Cells indexing format:– Cells(row, column), where both row and column are given

as integers (starting from 1)

– Cells(index)

Sub EnterValue() Worksheets("Sheet1").Cells(6, 1).Value = 10End Sub

Sub EnterValue() Worksheets(1).Range("A1:D3").Cells(7) .Value = "Here it is"End Sub

Referencing Cells Relative to Other Cells

ActiveCell.Offset(1, 2).Value = "Here it is"

Some useful methods/properties of Excel Classes

• Workbooks.Close – closes the active workbook• Workbooks.Count – returns the number of currently

open workbooks• Range(“A1”) is the same as Range(“A1”).Value• Cells(1,1) is the same as Cells(1,1).Value• Worksheets(1).Column(“A:B”).AutoFit • Worksheets(1).Range(“A1:A10”).Sort_• Workbooks.Open fileName:=“test.xls”

ArraysDim Students(1 to 5) As StringStudents(1) = “Jack” Students(2) = “Nick”

Multidimensional Arrays

Dim Grades(1 to 5,1 to 2) Grades(1,1)=“Jack”Grades(1,2)=“A”Grades(2,1)=“Nick”Grades(2,2)=“B”For i=1 to 2

MsgBox Grades(i,1) & “ got ” & Grades(i,2)NextMsgBox Grades(1, 1) & " got " & Grades(1, 2) & vbCrLf & _ Grades(2, 1) & " got " & Grades(2, 2)

Resizing the Arrays

Dim Grades(1 to 5,1 to 2) Grades(1,1)=“Jack”Grades(1,2)=“A”Grades(2,1)=“Nick”Grades(2,2)=“B”‘ Now ReDim the arrayReDim Grades(1 to 10,1 to 2) ‘previous values won’t be keptReDim Preserve Grades(1 to 10,1 to 2) ‘preserve previous values

Only the first dimension can be changed!

Upper & Lower Index Bounds of an Array

• Dim A(3): index from 0 to 3• Dim A(1 to 3): index from 1 to 3• Dim A(1 To 100, 0 To 3, -3 To 4)

– UBound(A, 1) – will return “100”– UBound(A, 2) – will return “3”– UBound(A, 3) – will return “4”– LBound(A, 1) – will return “1”– LBound(A, 2) – will return “0”– LBound(A, 3) – will return “-3”

VBA Control Structures - If• If Grade >= 90 Then MsgBox "You got an A"

ElseIf Grade >= 80 Then MsgBox "You got a B" ElseIf Grade >= 70 Then MsgBox "You got a C" Else

MsgBox "You are out of scope”End If Need to capture the rest of cases

VBA Control Structures – Select

• Select Case Grade        Case Is >= 90            MsgBox "You got an A         Case Is >= 80            MsgBox "You got an B”        Case Is >= 70            MsgBox "You got a C”         Case Else            MsgBox "You out of scope”End Select Need to capture the rest of cases

VBA Control Structures – LoopsSub factorial1()Dim NN = 10Cells(1, 1) = 1For i = N To 1 Step -1 Cells(1, 1) = Cells(1, 1) * iNextEnd Sub

Sub factorial3()Dim NN = 10i = NCells(1, 3) = 1Do Cells(1, 3) = Cells(1, 3) * i i = i - 1Loop While i >= 1End Sub

Sub factorial2()Dim NN = 10i = NCells(1, 2) = 1Do While i >= 1 Cells(1, 2) = Cells(1, 2) * i i = i - 1LoopEnd Sub

N!

Loop at least once

Loops for Collection Objects

Sub WorkSheetsLoop() Dim mySheet As Worksheet For Each mySheet In Worksheets MsgBox mySheet.Name Next mySheet

End Sub

Nested Loops Example

Sub NestedLoopExample() For i = 1 To 5 For j = 1 To 5 Cells(i, j) = "Row " & i & "   Col " & j Next j Next i

End Sub

Worksheet functions

Sub FuncExample()Range("D6") = Application. WorksheetFunction. Sum(Range("D1:D5"))‘ Can also use Application. Sum for shortEnd Sub

‘ Another way to get the sumRange("D6").Formula = "=SUM(D1:D5)"

Other Issues in VBA programming

• What if need to pass an array of arguments without knowing the number of arguments

Graphs

GraphsPrivate Sub cmdGenerate_Click()Range("B2:E13").Formula = "=RAND()*100"End Sub

Private Sub cmdPlot_Click() Create_Chart_SheetEnd Sub

Sub Create_Chart_Sheet() Charts.Add With ActiveChart .ChartType = xlColumnClustered .SetSourceData Source:=Sheets("Sheet4").Range("B1:E13") End WithEnd Sub

Graphs (Columnclusted)

Graphs (BarStacked)