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Possible Combinations
I have a group of 20 different numbers that I'm trying to determine all
possible combinations for. The trick is that I need something that will allow me to define the number of items in the combination pair. For example, I need to be able to pull all possible combinations of 2 numbers within a group of 20 items. Only I need to be able to do this from 2 numbers up to 20. I believe excel has the ability to do this, I am just unsure how to write it. I do not need all permutations such as (1,2) and (2,1). Since I will be taking the possible combinations and running a "sum" column down the side, these two combinations would yield the same result and are, therefore, unnecessary. |
#2
Posted to microsoft.public.excel.misc
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Possible Combinations
Copy everything below into a codemodule in a new workbook, and then follow the instructions. You'll
want to do C for Combinations, which will return the 190 combinations of 20 things taken 2 at a time.... If you can't get it to work, contact me privately, and I will send you a workbook. HTH, Bernie MS Excel MVP Option Explicit Dim vAllItems As Variant Dim Buffer() As String Dim BufferPtr As Long Dim Results As Worksheet ' ' Posted by Myrna Larson ' July 25, 2000 ' Microsoft.Public.Excel.Misc ' Subject: Combin ' ' 'Since you asked, here it is. It is generic, i.e. it isn't written specifically 'for a given population and set size, as yours it. It will do permutations or 'combinations. It uses a recursive routine to generate the subsets, one routine 'for combinations, a different one for permutations. 'To use it, you put the letter C or P (for combinations or permutations) in a 'cell. The cell below that contains the number of items in a subset. The Cells 'below are a list of the items that make up the population. They could be 'numbers, letters and symbols, or words, etc. 'You select the top cell, or the entire range and run the sub. The subsets are 'written to a new sheet in the workbook. ' ' Sub ListPermutationsOrCombinations() Dim Rng As Range Dim PopSize As Integer Dim SetSize As Integer Dim Which As String Dim N As Double Const BufferSize As Long = 4096 Worksheets("Sheet1").Range("A1").Select Set Rng = Selection.Columns(1).Cells If Rng.Cells.Count = 1 Then Set Rng = Range(Rng, Rng.End(xlDown)) End If PopSize = Rng.Cells.Count - 2 If PopSize < 2 Then GoTo DataError SetSize = Rng.Cells(2).Value If SetSize PopSize Then GoTo DataError Which = UCase$(Rng.Cells(1).Value) Select Case Which Case "C" N = Application.WorksheetFunction.Combin(PopSize, SetSize) Case "P" N = Application.WorksheetFunction.Permut(PopSize, SetSize) Case Else GoTo DataError End Select If N Cells.Count Then GoTo DataError Application.ScreenUpdating = False Set Results = Worksheets.Add vAllItems = Rng.Offset(2, 0).Resize(PopSize).Value ReDim Buffer(1 To BufferSize) As String BufferPtr = 0 If Which = "C" Then AddCombination PopSize, SetSize Else AddPermutation PopSize, SetSize End If vAllItems = 0 Application.ScreenUpdating = True Exit Sub DataError: If N = 0 Then Which = "Enter your data in a vertical range of at least 4 cells. " _ & String$(2, 10) _ & "Top cell must contain the letter C or P, 2nd cell is the number " _ & "of items in a subset, the cells below are the values from which " _ & "the subset is to be chosen." Else Which = "This requires " & Format$(N, "#,##0") & _ " cells, more than are available on the worksheet!" End If MsgBox Which, vbOKOnly, "DATA ERROR" Exit Sub End Sub Private Sub AddPermutation(Optional PopSize As Integer = 0, _ Optional SetSize As Integer = 0, _ Optional NextMember As Integer = 0) Static iPopSize As Integer Static iSetSize As Integer Static SetMembers() As Integer Static Used() As Integer Dim i As Integer If PopSize < 0 Then iPopSize = PopSize iSetSize = SetSize ReDim SetMembers(1 To iSetSize) As Integer ReDim Used(1 To iPopSize) As Integer NextMember = 1 End If For i = 1 To iPopSize If Used(i) = 0 Then SetMembers(NextMember) = i If NextMember < iSetSize Then Used(i) = True AddPermutation , , NextMember + 1 Used(i) = False Else SavePermutation SetMembers() End If End If Next i If NextMember = 1 Then SavePermutation SetMembers(), True Erase SetMembers Erase Used End If End Sub 'AddPermutation Private Sub AddCombination(Optional PopSize As Integer = 0, _ Optional SetSize As Integer = 0, _ Optional NextMember As Integer = 0, _ Optional NextItem As Integer = 0) Static iPopSize As Integer Static iSetSize As Integer Static SetMembers() As Integer Dim i As Integer If PopSize < 0 Then iPopSize = PopSize iSetSize = SetSize ReDim SetMembers(1 To iSetSize) As Integer NextMember = 1 NextItem = 1 End If For i = NextItem To iPopSize SetMembers(NextMember) = i If NextMember < iSetSize Then AddCombination , , NextMember + 1, i + 1 Else SavePermutation SetMembers() End If Next i If NextMember = 1 Then SavePermutation SetMembers(), True Erase SetMembers End If End Sub 'AddCombination Private Sub SavePermutation(ItemsChosen() As Integer, _ Optional FlushBuffer As Boolean = False) Dim i As Integer, sValue As String Static RowNum As Long, ColNum As Long If RowNum = 0 Then RowNum = 1 If ColNum = 0 Then ColNum = 1 If FlushBuffer = True Or BufferPtr = UBound(Buffer()) Then If BufferPtr 0 Then If (RowNum + BufferPtr - 1) Rows.Count Then RowNum = 1 ColNum = ColNum + 1 If ColNum 256 Then Exit Sub End If Results.Cells(RowNum, ColNum).Resize(BufferPtr, 1).Value _ = Application.WorksheetFunction.Transpose(Buffer()) RowNum = RowNum + BufferPtr End If BufferPtr = 0 If FlushBuffer = True Then Erase Buffer RowNum = 0 ColNum = 0 Exit Sub Else ReDim Buffer(1 To UBound(Buffer)) End If End If 'construct the next set For i = 1 To UBound(ItemsChosen) sValue = sValue & ", " & vAllItems(ItemsChosen(i), 1) Next i 'and save it in the buffer BufferPtr = BufferPtr + 1 Buffer(BufferPtr) = Mid$(sValue, 3) End Sub 'SavePermutation "Please HELP!!!" <Please wrote in message ... I have a group of 20 different numbers that I'm trying to determine all possible combinations for. The trick is that I need something that will allow me to define the number of items in the combination pair. For example, I need to be able to pull all possible combinations of 2 numbers within a group of 20 items. Only I need to be able to do this from 2 numbers up to 20. I believe excel has the ability to do this, I am just unsure how to write it. I do not need all permutations such as (1,2) and (2,1). Since I will be taking the possible combinations and running a "sum" column down the side, these two combinations would yield the same result and are, therefore, unnecessary. |
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