How to compare two arrays and write the uniue elements of one on a third array on VBA

Posted on 2009-04-02
Last Modified: 2013-11-25
The attached workbook contains two lists of customers:last year purchasers company last and this year purchasers

I want to write a sub that captures the existing lists in two arrays and then creates three new arrays:

1) One with customers who purchased last year only
2) One with customers who purchased this year only    
3) One with customers who purchased in both years.

After these new arrays have been filled, need to write their contents in columns D, E and F of the worksheet.
Question by:ksarafi1
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LVL 45

Accepted Solution

aikimark earned 500 total points
ID: 24074086
For some reason, the command button I found on your worksheet didn't behave like a regular control.  I added another command button and added the following code to its click event:
Private Sub CommandButton1_Click()
  Dim colLastYearOnly As New Collection
  Dim colThisYearOnly As New Collection
  Dim colBothYears As New Collection
  Dim rngThing As Range
  Dim rngFound As Range
  Dim varItem As Variant
  Dim lngRowOffset As Long
  'This code assumes that the two ranges are named LastYear and ThisYear
  For Each rngThing In Range("LastYear").Cells
    Set rngFound = Range("ThisYear").Find(rngThing.Text)
    If rngFound Is Nothing Then
      colLastYearOnly.Add rngThing.Text
      colBothYears.Add rngThing.Text
    End If
  For Each rngThing In Range("ThisYear").Cells
    Set rngFound = Range("LastYear").Find(rngThing.Text)
    If rngFound Is Nothing Then
      colThisYearOnly.Add rngThing.Text
    End If
  Application.ScreenUpdating = False
  'Populate the three columns
  Set rngThing = Range("D3")
  For Each varItem In colLastYearOnly
    lngRowOffset = lngRowOffset + 1
    rngThing.Offset(lngRowOffset, 0).Value = varItem
  Set rngThing = Range("E3")
  lngRowOffset = 0
  For Each varItem In colThisYearOnly
    lngRowOffset = lngRowOffset + 1
    rngThing.Offset(lngRowOffset, 0).Value = varItem
  Set rngThing = Range("F3")
  lngRowOffset = 0
  For Each varItem In colBothYears
    lngRowOffset = lngRowOffset + 1
    rngThing.Offset(lngRowOffset, 0).Value = varItem
  Application.ScreenUpdating = False
End Sub

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LVL 45

Expert Comment

ID: 24098620

How did this work for you?  

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Author Closing Comment

ID: 31566110
Thank you very much for your help. You solution was accurate and efficient.
LVL 45

Expert Comment

ID: 24099721

Glad I could help.

If you run this when either of the three lists shrinks, you might find some cells populated from the prior run.  To prevent this, add the following statement after the
    Application.ScreenUpdating = False


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