ACC2000: How to Change the Colors of a Chart Dynamically

You can change the colors of a chart dynamically to correspond with the data in the current record of a form or a report, or to reflect special conditions of the data. During the Current, Format, and Print events, the data displayed in a chart is not normally synchronized with the data in the current record of the form or the report. Because you must use a Visual Basic for Applications procedure to clear and reload the data of a chart every time that one of these events occurs, you can use the same procedure to change the colors of each data point on the graph.

The following example demonstrates how to create a chart whose colors are dynamic. Microsoft provides programming examples for illustration only, without warranty either expressed or implied. This includes, but is not limited to, the implied warranties of merchantability or fitness for a particular purpose. This article assumes that you are familiar with the programming language that is being demonstrated and with the tools that are used to create and to debug procedures. Microsoft support engineers can help explain the functionality of a particular procedure, but they will not modify these examples to provide added functionality or construct procedures to meet your specific requirements.

Modify the Query Product Sales for 1997

1. Start Microsoft Access and open the Product Sales for 1997 query in the sample database Northwind.mdb.
2. Add the Shippers table to the query. Microsoft Access automatically creates a join between the ShipVia field in the Orders table and the ShipperID field in the Shippers table.
3. Drag the CompanyName field from the Shippers table to the first empty column on the query design grid. Leave the Total row for this field set to the default value of Group By.
4. Save and close the query.

Create the Chart

1. Create a new form based on the Categories table. Include only the CategoryID and CategoryName fields in the detail section of the form.
2. On the Insert menu, click Chart to create a chart in the detail section of the form.
3. On the first screen of the Chart Wizard, click Queries and select Product Sales for 1997. Click Next.
4. Move the CompanyName field from the Available Fields list to the Fields for Chart list. Then move the ProductSales field from the Available Fields list to the Fields for Chart list. Click Next.
5. Click Next in the chart type screen to select the default type of Column Chart.
6. On the layout screen of the Chart Wizard, click Next.
7. Click OK if you receive the following message:
   You must add field CategoryID to your record source if you want to use this link.
8. In the Form Fields list, click CategoryName; in the Chart Fields list, click CategoryName, and then click Finish.
9. On the View menu, click Properties and change the Name property of the chart to chtColorChart.
10. Save the form as frmChartColors and switch to Form view. Note that the columns corresponding to each of the three shippers are all the same color.

Create the Event Procedure

1. Open frmChartColors in Design view, and on the View menu, click Code.
2. Type the following lines in the Declarations section of the class module if they are not already there:

    Option Compare Database
    Option Explicit
    Option Base 1
   					

3. On the Tools menu, click References.
4. In the References dialog box, scroll down the Available References list and select the Microsoft Graph 9.0 Object Library. Click OK, and then click Close and Return to Microsoft Access on the File menu.
5. On the Edit menu, click Select Form; then, Click Properties on the View menu to open the property sheet of the form.
6. Click the OnCurrent property box, and then click the Build (...) button. In the Choose Builder dialog box, click Code Builder, and then click OK.
7. Set the form's OnCurrent property to the following event procedure:

   Private Sub Form_Current()
   
      Dim chtObj As Object, strRowSource As String
      Dim rsRowSourceFiltered As Recordset
      Dim intMaxShippers As Integer
      Dim i As Integer, j As Integer
      Dim strArrShipperNames() As String
      Dim intArrShipperColors() As Integer
   
      ' The color integers are those that are used
      ' by the QBColor function to assign point colors.
   
      Const cFederal_Blue = 1
      Const cSpeedy_Green = 2
      Const cUnited_Red = 4
   
      intMaxShippers = 3
      ' Place all the shipper name values
      ' into an array.
      ReDim strArrShipperNames(intMaxShippers)
      strArrShipperNames(1) = "Federal Shipping"
      strArrShipperNames(2) = "Speedy Express"
      strArrShipperNames(3) = "United Package"
      ' Place the shipper color values
      ' into an array.
      ReDim intArrShipperColors(intMaxShippers)
      intArrShipperColors(1) = cFederal_Blue
      intArrShipperColors(2) = cSpeedy_Green
      intArrShipperColors(3) = cUnited_Red
   
      Set chtObj = Me!chtColorChart.Object
   
      ' In the chart's RowSource, insert a WHERE
      ' clause based on the value of the form
      ' field contained in the chart control's
      ' LinkMasterFields property.
      strRowSource = Left(Me!chtColorChart.RowSource, _
         InStr(Me!chtColorChart.RowSource, "GROUP BY") - 1) _ 
         & "WHERE " & Me!chtColorChart.LinkChildFields & _ 
         " = '" & Me(Me!chtColorChart.LinkMasterFields) & _
         "'" & " " & Right(Me!chtColorChart.RowSource, _
         Len(Me!chtColorChart.RowSource) _
         - InStr(Me!chtColorChart.RowSource, "GROUP BY") + 1)
      Set rsRowSourceFiltered = CurrentDb. _
         OpenRecordset(strRowSource, dbOpenSnapshot)
   
      ' Check to see if the filtered recordset has any records.
      If rsRowSourceFiltered.BOF And _
         rsRowSourceFiltered.EOF Then
            MsgBox "There are no records to chart."
            Exit Sub
      End If
   
      ' Clear the rows required for the maximum number of
      ' data rows. The first row contains the column
      ' headers. Data rows being at the second row.
      With chtObj.Application.DataSheet
         For i = 1 To intMaxShippers
            .Rows(i + 1).Include = False
         Next
      End With
   
      ' Ensure the RecordCount value is updated.
      rsRowSourceFiltered.MoveLast
      ' Populate the chart's datasheet with the
      ' filtered recordset, starting with the
      ' datasheet's second row.
      rsRowSourceFiltered.MoveFirst
      For i = 1 To rsRowSourceFiltered.RecordCount
         For j = 0 To rsRowSourceFiltered.Fields.Count - 1
            ' Assign data to the datasheet cells starting
            ' at row 2, column 1.
            chtObj.Application.DataSheet. _
               Cells(i + 1, j + 1).Value = _
               rsRowSourceFiltered.Fields(j).Value
         Next
         rsRowSourceFiltered.MoveNext
      Next
   
      ' Loop through the recordset containing
      ' the chart's filtered RowSource.
      rsRowSourceFiltered.MoveFirst
      i = 0
      While Not rsRowSourceFiltered.EOF
         ' Index i synchronizes the Points collection
         ' index with the current recordset row.
         i = i + 1
         ' Loop through the shipper names array and look
         ' for a match with the field names of the chart's
         ' filtered RowSource.
         For j = 1 To UBound(strArrShipperNames) ' 1-based
            ' The first field in the recordset contains
            ' the shipper name. Some shippers may not
            ' be in the filtered recordset.
            If rsRowSourceFiltered.Fields(0).Value _
               = strArrShipperNames(j) Then
                  ' Because every shipper has a corresponding color, the
                  ' arrays strArrShipperNames and intArrShipperColors
                  ' always contain the same number of elements.
                  ' Assign the color of the chart column, bar,
                  ' slice etc.
                  chtObj.SeriesCollection(1).Points(i). _
                     Interior.Color = _
                     QBColor(intArrShipperColors(j))
            End If
         Next
         rsRowSourceFiltered.MoveNext
      Wend
   
   End Sub
   					

8. Click Close and Return to Microsoft Access on the File menu.
9. Save the form and switch to Form view.
   
   Note that the three data points in the chart have different colors.