Excel Developer Tip

Identifying Unique Items in an Array or Range

Have you ever had to work with just the unique items in a range? If your data is in the form of a database, you can use the Advanced Filter command to extract the unique items from a single column. But if your data spans multiple columns, Advanced Filter won't work. And the Advanced Filter won't do you any good if your data is in a VBA array.

In this document I present a VBA function that accepts either a worksheet range object or a VBA array. The function returns either:

A variant array that consists of just the unique elements in the input array or range (or)
A single value: the number of unique elements in the input array or range.

Here's the syntax for the UniqueItems function (which is listed at the end of this document):

  UniqueItems(ArrayIn, Count)

```
ArrayIn: A range object, or an array
```
Count: (Optional) If True or omitted, the function returns a single value - the number of unique items in ArrayIn. If False, the function returns an array that consists of the unique items in ArrayIn.

Example 1

The subroutine below demonstrates UniqueItems. The routine generates 100 random integers and stores them in an array. This array is then passed to the UniqueItems function and a message box displays the number of unique integers in the array. The number will vary each time you run the subroutine.

Sub Test1()
    Dim z(1 To 100)
    For i = 1 To 100
        z(i) = Int(Rnd() * 100)
    Next i
    MsgBox UniqueItems(z, True)
End Sub

Example 2

The subroutine below counts the number of common elements in two worksheet ranges. It creates two arrays. Array1 consists of the unique items in A1:A16; Array2 consists of the unique items in B1:B16. A nested loop counts the number of items that are in both ranges.

Sub Test2()
    Set Range1 = Sheets("Sheet1").Range("A1:A16")
    Set Range2 = Sheets("Sheet1").Range("B1:B16")
    Array1 = UniqueItems(Range1, False)
    Array2 = UniqueItems(Range2, False)
    CommonCount = 0
    For i = LBound(Array1) To UBound(Array1)
        For j = LBound(Array2) To UBound(Array2)
            If Array1(i) = Array2(j) Then _
              CommonCount = CommonCount + 1
        Next j
    Next i
    MsgBox CommonCount
End Sub

Example 3

The UniqueItems function can also be used in worksheet formulas. The formula below returns the number of unique items in a range:

  =UniqueItems(A1:D21)

Example 4

To display the unique items in a range, you must array-enter the formula into a range of cells (use Ctrl+Shift+Enter). The result of the UniqueItems function is a horizontal array. If you would like to display the unique values in a column, you can use the TRANSPOSE function. The formula below (which is array-entered into a vertical range) returns the unique items in A1:D21.

  =TRANSPOSE(UniqueItems(A1:D21,FALSE))

Option Base 1

Function UniqueItems(ArrayIn, Optional Count As Variant) As Variant
'   Accepts an array or range as input
'   If Count = True or is missing, the function returns the number 
'   of unique elements
'   If Count = False, the function returns a variant array of unique 
'   elements
    
    Dim Unique() As Variant ' array that holds the unique items
    Dim Element As Variant
    Dim i As Integer
    Dim FoundMatch As Boolean
        
'   If 2nd argument is missing, assign default value
    If IsMissing(Count) Then Count = True
        
'   Counter for number of unique elements
    NumUnique = 0
        
'   Loop thru the input array
    For Each Element In ArrayIn
        FoundMatch = False

'       Has item been added yet?
        For i = 1 To NumUnique
            If Element = Unique(i) Then
                FoundMatch = True
                GoTo AddItem '(Exit For-Next loop)
            End If
        Next i
       
AddItem:
'       If not in list, add the item to unique list
        If Not FoundMatch Then
            NumUnique = NumUnique + 1
            ReDim Preserve Unique(NumUnique)
            Unique(NumUnique) = Element
        End If
    
    Next Element
    
'   Assign a value to the function
    If Count Then UniqueItems = NumUnique Else UniqueItems = Unique
End Function