Excel: Copy cells within a column based on duplicates from another column

Question

I'd like to copy data from Column A based on duplicates in Column B and past them in Column C either separated by comma or listed horizontally. Please see example below:

Column A   Column B   Column C (Output)
1          A          1,2
2          A          
3          B          3,4,5
4          B
5          B
6          C          6
7          D          7

Answer 1

Sub CopyCells()
Application.ScreenUpdating = False
Dim i As Long, v As Variant, fVisRow As Long, rng As Range, Val As String
v = Range("B2", Range("B" & Rows.Count).End(xlUp)).Value
With CreateObject("Scripting.Dictionary")
    For i = 1 To UBound(v, 1)
        If Not .Exists(v(i, 1)) Then
            .Add v(i, 1), Nothing
            With Range("A1").CurrentRegion
                .AutoFilter 2, v(i, 1)
                fVisRow = .Range("A2", Range("A" & Rows.Count).End(xlUp)).SpecialCells(xlCellTypeVisible).Cells(1, 1).Row
                For Each rng In Range("A2", Range("A" & Rows.Count).End(xlUp)).SpecialCells(xlCellTypeVisible)
                    If Val = "" Then Val = rng Else Val = Val & ", " & rng
                Next rng
                Range("C" & fVisRow) = Val
                Val = ""
            End With
        End If
    Next i
End With
Range("A1").AutoFilter
Application.ScreenUpdating = True
End Sub

Answer 2

Try this if you have excel 365.

=TEXTJOIN(",",TRUE,FILTER($E$16:$E$22,$F$16:$F$22=G16))