References. Arrays. Default array bounds. Array example. Array usage. Shepherd, pp (Arrays) Shepherd, Chapters 12, 13

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1 ENGG1811 UNSW, CRICOS Provider No: 00098G W7 slide 1 References ENGG1811 Computing for Engineers Week 7 Arrays, Objects and Collections; Using the Macro Recorder Shepherd, pp (Arrays) Shepherd, Chapters 12, 13 ENGG1811 UNSW, CRICOS Provider No: 00098G W7 slide 2 Arrays Default array bounds Arrays are groups of variables of the same type Each element of an array has a unique index, representing its position in the array, usually starting at 0 or 1 Declaration specifies type and bounds: Const MAX_SAMPLES = 10 Const ALPHA_SIZE = 26 Const MONTHS_PER_YEAR = 12 Dim dblsamples(1 To MAX_SAMPLES) As Double Dim freq(0 To ALPHA_SIZE-1) As Integer ' letter frequencies Dim daysin(1 To MONTHS_PER_YEAR) As Integer ' days in each month If the lower bound is omitted, a default value is used The default value is normally 0 Can be changed with Option Base directive at top of module Option Base 1 ' omitted lower bounds now = 1 Const MAX_SAMPLES = 200 Dim dblsamples(max_samples) As Double ' valid index 1..MAX_SAMPLES Recommended approach: specify both bounds ENGG1811 UNSW, CRICOS Provider No: 00098G W7 slide 3 ENGG1811 UNSW, CRICOS Provider No: 00098G W7 slide 4 Array usage Array example Arrays are often visualised as a line of variables: daysin index Access a particular element using the array name and an index expression in parentheses Dim idx As Integer Dim dblsample(1 To MAX_SAMPLE) As Double ' load array from first column of worksheet For idx = 1 To MAX_SAMPLE dblsample(idx) = ActiveSheet.Cells(idx,1).Value Next idx For statement mimics array declaration For any date, calculate the day of the year (1 Jan = day 1, 31 Dec = day 365 or 366) as used in business and financial systems Analysis: the day of the year = the number of days in all the previous months, plus the day of the month. For example, in a non-leap year, Anzac Day (25 April) is day ( ) + 25 = 115. Leap year adjustment: add 1 to day if past February in a leap year. That's all. Programming: use an array to hold the days in each month (constants), accumulate sums ENGG1811 UNSW, CRICOS Provider No: 00098G W7 slide 5 ENGG1811 UNSW, CRICOS Provider No: 00098G W7 slide 6

2 ENGG1811 UNSW, CRICOS Provider No: 00098G W7 slide 7 Pseudocode Given variables day, month, year: Initialise daysin array Set sum to the sum of the days in all months < month Add day to sum If year is a leap year And month > February Add 1 to sum result is stored in sum The step Set sum is a substantial subtask with its own pseudocode (written as a function) Set s to 0 For each m from 1 to month-1 add daysin(m) to s return the value in s Initialising the daysin array Unfortunately VBA doesn't support constant arrays, or allow direct assignment of arrays. However, it does have a function that constructs an array and returns it as a Variant, which can be indexed Private Sub InitDaysIn() Dim constlist as Variant Dim m As Integer You don't need to know this, it's just to make the demo work constlist = Array(31, 28, 31, 30, 31, 30, _ 31, 31, 30, 31, 30, 31) For m = 1 To MONTHS_PER_YEAR daysin(m) = constlist(m) Next m End Sub ENGG1811 UNSW, CRICOS Provider No: 00098G W7 slide 8 Partial solution Arrays and Cells Function DaysToEndOf(month As Integer) As Integer Dim m As Integer ' a month number Dim s As Integer ' sum of days in 1..m s = 0 For m = To s = Next m DaysToEndOf = s End Function ' return answer Complete solution left as an exercise. Use a leap-year function and a named constant for February. The Excel model allows access to worksheet cells as a two-dimensional array ActiveSheet.Cells(row,col).Value = 42 Arrays are a more general programming structure, independent of the application's user-accessible data like worksheets and documents Arrays are not visible like cells, can be used for intermediate storage Like other variables, can be local to a module or to a procedure. ENGG1811 UNSW, CRICOS Provider No: 00098G W7 slide 9 ENGG1811 UNSW, CRICOS Provider No: 00098G W7 slide 10 Resizing Arrays Arrays can be dynamically sized if needed with this statement (not declaration): Redim Preserve dblsample(1 To 10*MAX_SAMPLE) Preserve retain elements up to new limit Current array bounds are returned by the built-in functions LBound(arr) and UBound(arr): For idx = LBound(dblSample) To UBound(dblSample) dblsample(idx) = dblsample(idx) / 2 Next idx Objects VBA is a mixture of conventional procedural notation process dataobject or evaluate(dataobject) and object oriented programming dataobject.method Excel data is represented by objects that have properties and to which methods are applied: Methods are procedures that are associated with a type of object and are applied to objects of that kind ActiveSheet.Cells(row,col).Formula = "=B3/4" applies the ActiveSheet.Hide Hide method to the active sheet ActiveSheet.Rows(2).Clear assigns to the Formula property of the cell array representing all rows second element (= row 2) applies the Clear method to the object (row 2 of the active sheet) ENGG1811 UNSW, CRICOS Provider No: 00098G W7 slide 11 ENGG1811 UNSW, CRICOS Provider No: 00098G W7 slide 12

3 ENGG1811 UNSW, CRICOS Provider No: 00098G W7 slide 13 Objects, continued Most important object types are Application one instance representing the Excel state, provides methods to create dialogue boxes and other window objects Workbook Worksheet Range any single cell or group of cells The on-line manual describes their properties and methods, but the Macro Recorder (later slide) allows us to see what object manipulation corresponds to particular user interaction Collections Array concept relies on strict ordering of elements If elements can be named, get more general way of describing the group A Collection is an array-type object indexed either by number or by name Properties include: Count (number of elements) Methods include: Add (a named element, relatively positioned) Item (retrieve "current" element) ENGG1811 UNSW, CRICOS Provider No: 00098G W7 slide 14 Collections, continued Some Excel objects are collections Application.Workbooks ' (base type: Workbook) Application.ActiveWorkbook.WorkSheets' (Worksheet) ActiveWorkbook.Sheets ' (Chart or Worksheet) ActiveSheet.Charts ' Displayed charts ActiveSheet.Shapes ' Drawing objects: later slide Examples Sheets.Add Name:="New sheet", After:=Sheets(3) Debug.Print Sheets(1).Name (in full: Debug.Print Application.ActiveWorkbook.Sheets(1).Name) Debug.Print Workbooks.Count Manipulating Collections Declare variable to reference elements Dim wks As Worksheet Object assignment uses the Set keyword Set wks = Sheets(1) this is easy to forget Access object properties and methods: wks.columns(col).clear ' prop/method wks.unhide ' method wks.cells(row,col).formula = "=A1+1" ENGG1811 UNSW, CRICOS Provider No: 00098G W7 slide 15 ENGG1811 UNSW, CRICOS Provider No: 00098G W7 slide 16 Iterating over a Collection Special notation to iterate over elements: For Each wks In ActiveWorkbook.Sheets Debug.Print wks.name Next wks Equivalent (but preferable) to: For idx = 1 To ActiveWorkbook.Sheets.Count Set wks = Sheets(idx) Debug.Print wks.name Next idx With Statement Sometimes the same object needs to be referenced several times in succession ActiveSheet.Cells(row,col) = intval1 ActiveSheet.Cells(row+1,col) = intval2 ActiveSheet.Cells(row+2,col) = intval3 Use a With statement for the common prefix: With ActiveSheet.Cells(row,col) = intval1.cells(row+1,col) = intval2.cells(row+2,col) = intval3 note dot is retained in the shortened reference ENGG1811 UNSW, CRICOS Provider No: 00098G W7 slide 17 ENGG1811 UNSW, CRICOS Provider No: 00098G W7 slide 18

4 ENGG1811 UNSW, CRICOS Provider No: 00098G W7 slide 19 Note Ranges The following topics contain a lot of detail Most of the detail can be found in Help screens or reference books You don't have to learn the detail, but you must understand the way that these structures are put together Lab work will guide you through the essential skills needed to manipulate objects, including referencing ranges using the macro recorder creating and manipulating drawings but you need to follow what s presented here! The Range type represents a rectangular group of (one or more) cells on a worksheet Can be referred to in many ways Single cell, separate indexes:.cells(row,col) Single cell, RC format:.range("b5") Single row, index:.rows(row) Single column, index:.column(col) Row/column block:.rows("4:6").columns("a:c") Any block, RC format:.range("b4:h7") Named range:.range("polynomial") Derived from another range: ActiveCell.EntireRow Whole sheet:.cells ENGG1811 UNSW, CRICOS Provider No: 00098G W7 slide 20 Some Range Properties Borders Object representing outline Comment Comment text Font Text font Formula Formula as a string (such as "=A$1/24") Height, Width Height or width in screen units HorizontalAlignment xlleft/xlcenter/xlright Interior Object representing cell background Left, Top Position of range on sheet, in screen units Locked True Cells can't be changed by the user Name Name if defined NumberFormat Name or specification of display format Value Stored value Note: Properties of a multi-cell range are undefined if the cell properties are not consistent Some Range Methods AutoFilter Apply column filters Calculate Re-evaluate formulae Clear, ClearComments Remove cell contents or comments Copy, Cut Copy to clipboard, Cut=remove after pasting Delete Remove cells and shift in FillDown, FillRight Apply fill operations Find Search for cell contents matching value Offset Generate reference to nearby cell GoalSeek Apply Excel's Goal Seek (range must be one cell) Merge Merge cells, retaining value from top left cell PasteSpecial Paste from Clipboard with optional transforms Replace Replace cell contents Select Make range the current selection (available as the Selection object) Sort Reorder rows (has many parameters) ENGG1811 UNSW, CRICOS Provider No: 00098G W7 slide 21 ENGG1811 UNSW, CRICOS Provider No: 00098G W7 slide 22 Range as a Collection Macro Recorder ' From an example at ' use in worksheet: =sumifcoloured(a1:c6) Function SumIfColoured(rngCells As Range) As Double Dim cell As Object Dim sum As Double sum = 0 For Each cell In rngcells If cell.interior.colorindex <> xlnone Then sum = sum + Cell.Value End If Next cell SumIfColoured = sum End Function Almost everything the user can do with Excel can be tracked as a Macro and replayed* Macros are stored as VBA procedures Macros can be edited (or cannibalised!) to adapt or generalise their purpose Effective way to find out how to achieve a particular effect (especially as VBA Help is poor) * unfortunately, Excel 2007 does not record drawing operations, whereas Excel 2003, 2002, 2000 and 97 did. ENGG1811 UNSW, CRICOS Provider No: 00098G W7 slide 23 ENGG1811 UNSW, CRICOS Provider No: 00098G W7 slide 24

5 ENGG1811 UNSW, CRICOS Provider No: 00098G W7 slide 25 Using the Macro Recorder Macro Recording examples Menu path Tools Macro Record New Macro Name, location and optional shortcut key can be set: Creates new Module if necessary Tracks all menu functions and relevant mouse activity (cell selections, dialogue responses, etc) When finished, Tools Macro Stop Recording View/edit macro with VBE Demonstration includes Changing appearance: set the background of cells, border appearance etc Resize cells, autofit etc Move data around (via Selection) Create and modify a chart Invoke Goal Seek or Solver Create drawings (explored in the lab) ENGG1811 UNSW, CRICOS Provider No: 00098G W7 slide 26 Example: Cell operations Apply the following to a two-column table such as the solution to Lab 8 Part C: 1. Adjust the indent of column B; 2. Change the background of the header cells 3. Change the font and colour of the header cells VBA Created by Recorder Columns("B:B").Select With Selection.HorizontalAlignment = xlleft.verticalalignment = xlbottom.wraptext = False.Orientation = 0.AddIndent = False.IndentLevel = 1.ShrinkToFit = False.ReadingOrder = xlcontext.mergecells = False Range("A1:B1").Select With Selection.Interior.ColorIndex = 9.Pattern = xlsolid Selection.Font.ColorIndex = 6 With Selection.Font ' other font changes Change properties using the Selection object Colour index values range from 1 to 56 Shows all properties, even though we only changed IndentLevel Colour picker is not in index order! For information about colour indexes, see ENGG1811 UNSW, CRICOS Provider No: 00098G W7 slide 27 ENGG1811 UNSW, CRICOS Provider No: 00098G W7 slide 28 Recorder vs Human The Macro Recorder makes extensive use of the Selection object (since the user must select elements before using them) Humans can refer directly to the affected object: Const COL_DATA = 2 With Columns(COL_DATA) ' = Columns("B:B").HorizontalAlignment = xlleft Humans can code iteration, Recorder can't Humans can use local variables, Recorder can't Humans can use Const definitions and meaningful names, Recorder can't Shapes The Office family supports drawing operations, including lines, filled polygons, predefined shapes Represented by Shape objects, thus can be manipulated by VBA To create a drawing with Excel: Tools Options View and deselect Gridlines Make sure Drawing toolbar is enabled Select AutoShape, click to position and drag to set size Lines, rectangles, circles, stroke and fill etc on toolbar Connectors are especially useful as they snap to vertices Use Macro Recorder to create sample code Not certified with Excel2007 ENGG1811 UNSW, CRICOS Provider No: 00098G W7 slide 29 ENGG1811 UNSW, CRICOS Provider No: 00098G W7 slide 30

6 ENGG1811 UNSW, CRICOS Provider No: 00098G W7 slide 31 Shapes in VBA Recorder shows that Coordinate system is Cartesian (which way is Y?) Units are points (1/72 inch, approx 28 pts per cm) Drawing elements are members of the Shapes collection belonging to the active sheet New shapes are created using the AddShape method (built-in procedure) with distinctive args for shape type and characteristics Many shape types (type AutoShapeType to Help, then click on msoautoshapetype for list) Changes to properties with user interface is via Selection object (though not required in VBA) Identifying Shapes Create most shapes with Dim shp As Shape Set shp = ActiveSheet.Shapes.AddShape(type, _ left, top, width, height) Set shp = ActiveSheet.Shapes.AddTextbox( ) ' then use shp to set properties Each shape is given a name and number according to its type ("Rectangle 1", "AutoShape 5"), and each has an index, equal to the collection size after Add lastshape = ActiveSheet.Shapes.Count Can later use the index to reference the shape: ActiveSheet.Shapes(lastShape) Keeping track of all shapes this way can be tricky (but arrays help) ENGG1811 UNSW, CRICOS Provider No: 00098G W7 slide 32 Shape Operations Applying stroke (outline) With object.line.weight = 1.5 ' in points.style = msolinesingle ' default.dashstyle = msolinesquaredot.forecolor.scheme = 12 ' dark blue stroke Also BeginArrowheadStyle; Width (Wide/Medium/Narrow) as well as Length (Long/Medium/Short).EndArrowheadStyle = msoarrowheadtriangle.endendarrowheadlength = msoarrowheadlengthmedium Applying fills.fill.forecolor.rgb = RGB(red, blue, green) ' Fill.Transparency = 0# ' 0# = 0.0 (VB idiom).fill.visible = False ' to hide (also.line) Text Boxes Text is held in boxes (with stroke and fill) object.characters.text = "Power Station" With object.characters.font.name = "Arial Narrow".FontStyle = "Bold".Size = 11 Font properties of substrings object.characters(start:=3, Length:=2) _.Font.Subscript = True Remove box:.fill.visible = False.Line.Visible = False ENGG1811 UNSW, CRICOS Provider No: 00098G W7 slide 33 ENGG1811 UNSW, CRICOS Provider No: 00098G W7 slide 34 Example: Venn Diagram Summary Algorithm is trivial (but calcs are fiddly) Draw canvas Calculate geometry Draw first set Draw second set Draw labels (4 sub calls) Draw pointer Sub DrawSet(dblRadius As Double, dblx As Double, dbly As Double, _ lngcolour As Long, dbltrans As Double) Dim shpset As Shape Set shpset = ActiveSheet.Shapes.AddShape(msoShapeOval, dblx - dblradius, _ dbly - dblradius, 2 * dblradius, 2 * dblradius) shpset.line.weight = 1.5 With shpset.fill.forecolor.rgb = lngcolour.transparency = dbltrans End Sub Arrays store a sequence of multiple values Array elements are indexed by a small integer Collections store a set or sequence of objects, referenced by either name or index Objects enable access to complex data managed by the application A Range object represents part of a worksheet, can also be viewed as a collection of cells Macro recorder creates editable VBA from user interaction with the application ENGG1811 UNSW, CRICOS Provider No: 00098G W7 slide 35 ENGG1811 UNSW, CRICOS Provider No: 00098G W7 slide 36