Selecting Random Names

A common task for many people is to pick a number of random names from a large list. For instance, you may be running a contest for your community, and you have 1,000 people that have entered. With their names in each row of a table, you may be wondering how to select a certain number of the names randomly.

As is often the case with Excel, there are a number of different approaches you can take. Each approach examined in this tip assumes that the names you need to select from are listed in cells A1 through A1000. Of course, your range of names could be shorter or longer, but the point is that they are in contiguous cells in column A. The examples also assume that you need to select 15 names at random from the list.

The first approach is to use the INDEX function. Enter the following formula in cells B1:B15:

=INDEX(A:A,INT((RAND()*1000)+1),1)

A similar formula uses the OFFSET function:

=OFFSET($A$1,ROUNDUP(RAND()*1000,0),0,1,1)

It is possible, but not probable, that you will get the same name twice in the resulting list. (The improbability comes because of the size of the original list. The larger the list, the less probable there will be duplicates in the extracted list.) If you do get a duplicate name, then simply force a recalculation of your worksheet by pressing F9. Each time your recalculate, the list of extracted names is regenerated.

Another potential approach requires the use of multiple columns. Simply follow these steps:

1. Enter =RAND() in cell B1.
2. Enter the following formula in cell C1:

     =RANK(B1,$B$1:$B$1000)

3. Select the range B1:C1, and fill down to row 1000.
4. Select the range B1:C1000.
5. Press Ctrl+C to copy the range to the Clipboard.
6. Choose Paste Special from the Edit menu. Excel displays the Paste Special dialog box. (See Figure 1.)



Figure 1. The Paste Special dialog box.

7. Make sure the Values radio button is selected.
8. Click on OK. You now have static values in B1:C1000, which means they won't change every time the worksheet is recalculated.
9. Select a cell in column C.
10. Choose Sort from the Data menu. Excel displays the Sort dialog box. (See Figure 2.)



Figure 2. The Sort dialog box.

11. Click on OK. The table (range A1:C1000) is sorted according to the values in column C.

The result is that column C now contains a ranking of all the random numbers in column B. The first 15 rows contain your random names.

In this approach you could also have left out column C completely and simply sorted your list based on the static random values in column B. Again, the top 15 would be your random names.

Of course, there are any number of macro solutions you could use for this problem. The coding of any macro will be similar, relying on VBA's RND function to generate random numbers. Of all the possible macro solutions, perhaps the following is the most unique and offers some advantages not available with the workbook solutions discussed so far:

Sub GetRandom()
    Dim iRows As Integer
    Dim iCols As Integer
    Dim iBegRow As Integer
    Dim iBegCol As Integer
    Dim J As Integer
    Dim sCells As String
    
    Set TempDO = New DataObject
    
    iRows = Selection.Rows.Count
    iCols = Selection.Columns.Count
    iBegRow = Selection.Row
    iBegCol = Selection.Column
    
    If iRows < 16 Or iCols > 1 Then
        MsgBox "Too few rows or too many columns"
    Else
        Randomize Timer
        sCells = ""
        For J = 1 To 15
            iWantRow = Int(Rnd() * iRows) + iBegRow
            sCells = sCells & Cells(iWantRow, iBegCol) & vbCrLf
        Next J
        TempDO.SetText sCells
        TempDO.PutInClipboard
    End If
End Sub

To use this macro, just select the names from which you want to select the 15 random names. In the examples thus far, you would select the range A1:A1000. The macro then pulls 15 names at random from the cells, and puts them in the Clipboard. When you run the macro, you can then paste the contents of the Clipboard where ever you want. Every time the macro is run, a different group of 15 is selected.

ExcelTips is your source for cost-effective Microsoft Excel training. This tip (2811) applies to Microsoft Excel 97, 2000, 2002, and 2003. You can find a version of this tip for the ribbon interface of Excel (Excel 2007 and later) here: Selecting Random Names.