Finding and counting number of duplicates

Question

I have a spreadsheet with a column called NumberID that has about 50k records. I am aware that there are duplicates however with scrolling up/down it takes forever to find anything plus often times excel is being somewhat slow. I'm trying to write a quick snippet of code to be able to find and count the number of duplicates.

I'm trying to write a quick way of doing it, basically my data is from rows 20 to 48210 and I'm trying to find a number total duplicate records.

Dim lastRow As Long
Dim matchFoundIndex As Long
Dim iCntr As Long
Dim count As Long
count = 0
lastRow = Range("B48210").End(xlUp).Row
For iCntr = 1 To lastRow
    If Cells(iCntr, 1) <> "" Then
       matchFoundIndex = WorksheetFunction.Match(Cells(iCntr, 1), Range("B20:B" & lastRow), 0)
        If iCntr <> matchFoundIndex Then
            count = count + 1
        End If
     End If
Next

MsgBox count

Here im getting an error on = WorkSheetFunction.Match - i found that this property can be used to accomplish what I'm trying to do. The error says

Unable to get the match property for the worksheetfunction class.

Someone have an idea? My vba has been rusty

Answer 1

since you want to "count the number of duplicates", a very fast way of doing that is exploiting RemoveDuplicates() method of Range object, like follows:

Option Explicit

Sub main()
    Dim helperCol As Range
    Dim count As Long

    With Worksheets("IDs") '<--| reference your relevant sheet (change "IDs" to youtr actual sheet name)
        Set helperCol = .UsedRange.Resize(, 1).Offset(, .UsedRange.Columns.count) '<--| set a "helper" range where to store unique identifiers
        With .Range("A1", .Cells(.Rows.count, 1).End(xlUp)) '<-- reference "IDs" column from row 1 (header) to last not empty cell
            helperCol.Value = .Value '<--| copy identifiers to "helper" range
            helperCol.RemoveDuplicates Columns:=1, Header:=xlYes '<--| remove duplicates in copied identifiers
            count = .SpecialCells(xlCellTypeConstants).count - helperCol.SpecialCells(xlCellTypeConstants).count '<--| count duplicates as the difference between original IDs number and unique ones
        End With
        helperCol.ClearContents '<--| clear "helper" range
    End With
    MsgBox count & " duplicates"
End Sub