Fuzzy Matching - new version plus explanation

al_b_cnu

Well-known Member
Joined
Jul 18, 2003
Messages
4,546
It has been a while since I originally posted my Fuzzy matching UDF’s on the board, and several variants have appeared subsequently.

I thought it time to ‘put the record straight’ & post a definitive version which contains slightly more efficient code, and better matching algorithms, so here it is.

Firstly, I must state that the Fuzzy matching algorithms are very CPU hungry, and should be used sparingly. If for instance you require to lookup a match for a string which starts with, contains or ends with a specified value, this can be performed far more efficiently using the MATCH function:
Fuzzy Examples.xls
ABCDE
1Starts WithEndsContains
2BilljelenBill
3Mr Bill Jelen433
4Bill Jelen
5Joe Bloggs
6Fred Smith
MATCH Example


... Continued ...
 
Hi,

True, you dont.

Maybe we need a function "FuzzyCount" which returns the number of entries above the NFPercent Threshold- I'll write it tonight if you like.

One minor concern is that all this is going to use up an awful lot of processing power.
 
Upvote 0

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Wow, cheers Alan, that would be absolutely brilliant. As for the CPU intensive bit, given that I need to run this once a week and can run it over the weekend, this shouldn't be a big deal. I did look at your code and had no doubts that it would be CPU intensive to do the fuzzy match on every cell.
 
Upvote 0
Hi,

ok, here's the code with the additional (simple) UDF "FuzzyCount":
Code:
Option Explicit

Type RankInfo
    Offset As Long
    Percentage As Single
End Type

Dim mudRankData() As RankInfo
Dim mlBestMatchPtr As Long

Dim TopMatch         As Long
Dim strCompare       As String

Function FuzzyCount(ByVal LookupValue As String, _
                      ByVal TableArray As Range, _
                      Optional NFPercent As Single = 0.05, _
                      Optional Algorithm As Integer = 3) As Long
'**********************************************************************
'** Simple count of (Fuzzy) Matching strings >= NFPercent threshold  **
'**********************************************************************
Dim lMatchCount As Long

Dim rCur As Range

Dim sString1 As String
Dim sString2 As String

'** Normalise lookup value **
sString1 = LCase$(Application.Trim(LookupValue))

For Each rCur In Intersect(TableArray.Resize(, 1), Sheets(TableArray.Parent.Name).UsedRange)

    '** Normalise current Table entry **
    sString2 = LCase$(Application.Trim(CStr(rCur)))
    
    If sString2 <> "" Then
        If FuzzyPercent(String1:=sString1, _
                        String2:=sString2, _
                        Algorithm:=Algorithm, _
                        Normalised:=True) >= NFPercent Then
            lMatchCount = lMatchCount + 1
        End If
    End If
Next rCur

FuzzyCount = lMatchCount

End Function

Function FuzzyPercent(ByVal String1 As String, _
                      ByVal String2 As String, _
                      Optional Algorithm As Integer = 3, _
                      Optional Normalised As Boolean = False) As Single
'*************************************
'** Return a % match on two strings **
'*************************************
Dim intLen1 As Integer, intLen2 As Integer
Dim intCurLen As Integer
Dim intTo As Integer
Dim intPos As Integer
Dim intPtr As Integer
Dim intScore As Integer
Dim intTotScore As Integer
Dim intStartPos As Integer
Dim sngScore As Single
Dim strWork As String

'-------------------------------------------------------
'-- If strings havent been normalised, normalise them --
'-------------------------------------------------------
If Normalised = False Then
    String1 = LCase$(Application.Trim(String1))
    String2 = LCase$(Application.Trim(String2))
End If

'----------------------------------------------
'-- Give 100% match if strings exactly equal --
'----------------------------------------------
If String1 = String2 Then
    FuzzyPercent = 1
    Exit Function
End If

intLen1 = Len(String1)
intLen2 = Len(String2)

If intLen1 = 0 Or intLen2 = 0 Then
    FuzzyPercent = 0
    Exit Function
End If

'----------------------------------------
'-- Give 0% match if string length < 2 --
'----------------------------------------
If intLen1 < 2 Then
    FuzzyPercent = 0
    Exit Function
End If

intTotScore = 0                   'initialise total possible score
intScore = 0                      'initialise current score

'--------------------------------------------------------
'-- If Algorithm = 1 or 3, Search for single characters --
'--------------------------------------------------------
If (Algorithm And 1) <> 0 Then
    If intLen1 < intLen2 Then
        FuzzyAlg1 String1, String2, intScore, intTotScore
    Else
        FuzzyAlg1 String2, String1, intScore, intTotScore
    End If
End If

'-----------------------------------------------------------
'-- If Algorithm = 2 or 3, Search for pairs, triplets etc. --
'-----------------------------------------------------------
If (Algorithm And 2) <> 0 Then
    If intLen1 < intLen2 Then
        FuzzyAlg2 String1, String2, intScore, intTotScore
    Else
        FuzzyAlg2 String2, String1, intScore, intTotScore
    End If
End If

'------------------------------------------------------
'-- If Algorithm = 4,5,6,7, use Dan Ostander's code. --
'------------------------------------------------------
If (Algorithm And 4) <> 0 Then
    If intLen1 < intLen2 Then
        sngScore = FuzzyAlg4(String1, String1)
    Else
        sngScore = FuzzyAlg4(String2, String1)
    End If
    intScore = intScore + (sngScore * 100)
    intTotScore = intTotScore + 100
End If

FuzzyPercent = intScore / intTotScore

End Function

Private Sub FuzzyAlg1(ByVal String1 As String, _
                      ByVal String2 As String, _
                      ByRef Score As Integer, _
                      ByRef TotScore As Integer)
Dim intLen1 As Integer, intPos As Integer, intPtr As Integer, intStartPos As Integer

intLen1 = Len(String1)
TotScore = TotScore + intLen1              'update total possible score
intPos = 0
For intPtr = 1 To intLen1
    intStartPos = intPos + 1
    intPos = InStr(intStartPos, String2, Mid$(String1, intPtr, 1))
    If intPos > 0 Then
        If intPos > intStartPos + 3 Then     'No match if char is > 3 bytes away
            intPos = intStartPos
        Else
            Score = Score + 1          'Update current score
        End If
    Else
        intPos = intStartPos
    End If
Next intPtr
End Sub
Private Sub FuzzyAlg2(ByVal String1 As String, _
                        ByVal String2 As String, _
                        ByRef Score As Integer, _
                        ByRef TotScore As Integer)
Dim intCurLen As Integer, intLen1 As Integer, intTo As Integer, intPtr As Integer, intPos As Integer
Dim strWork As String

intLen1 = Len(String1)
For intCurLen = 1 To intLen1
    strWork = String2                          'Get a copy of String2
    intTo = intLen1 - intCurLen + 1
    TotScore = TotScore + Int(intLen1 / intCurLen)  'Update total possible score
    For intPtr = 1 To intTo Step intCurLen
        intPos = InStr(strWork, Mid$(String1, intPtr, intCurLen))
        If intPos > 0 Then
            Mid$(strWork, intPos, intCurLen) = String$(intCurLen, &H0) 'corrupt found string
            Score = Score + 1     'Update current score
        End If
    Next intPtr
Next intCurLen

End Sub
Private Function FuzzyAlg4(strIn1 As String, strIn2 As String) As Single

Dim L1               As Integer
Dim In1Mask(1 To 24) As Long     'strIn1 is 24 characters max
Dim iCh              As Integer
Dim N                As Long
Dim strTry           As String
Dim strTest          As String

TopMatch = 0
L1 = Len(strIn1)
strTest = UCase(strIn1)
strCompare = UCase(strIn2)
For iCh = 1 To L1
    In1Mask(iCh) = 2 ^ iCh
Next iCh      'Loop thru all ordered combinations of characters in strIn1
For N = 2 ^ (L1 + 1) - 1 To 1 Step -1
    strTry = ""
    For iCh = 1 To L1
        If In1Mask(iCh) And N Then
            strTry = strTry & Mid(strTest, iCh, 1)
        End If
    Next iCh
    If Len(strTry) > TopMatch Then FuzzyAlg4Test strTry
Next N
FuzzyAlg4 = TopMatch / CSng(L1)
End Function
Sub FuzzyAlg4Test(strIn As String)

Dim l          As Integer
Dim strTry   As String
Dim iCh        As Integer

l = Len(strIn)
If l <= TopMatch Then Exit Sub
strTry = "*"
For iCh = 1 To l
    strTry = strTry & Mid(strIn, iCh, 1) & "*"
Next iCh
If strCompare Like strTry Then
    If l > TopMatch Then TopMatch = l
End If
End Sub

Function FuzzyVLookup(ByVal LookupValue As String, _
                      ByVal TableArray As Range, _
                      ByVal IndexNum As Integer, _
                      Optional NFPercent As Single = 0.05, _
                      Optional Rank As Integer = 1, _
                      Optional Algorithm As Integer = 3, _
                      Optional AdditionalCols As Integer = 0, _
                      Optional LookupColOffset As Integer = 0, _
                      Optional GroupColOffset As Integer = 0, _
                      Optional GroupValue As Variant = "") As Variant
'********************************************************************************
'** Function to Fuzzy match LookupValue with entries in                        **
'** column 1 of table specified by TableArray.                                 **
'** TableArray must specify the top left cell of the range to be searched      **
'** The function stops scanning the table when an empty cell in column 1       **
'** is found.                                                                  **
'** For each entry in column 1 of the table, FuzzyPercent is called to match   **
'** LookupValue with the Table entry.                                          **
'** 'Rank' is an optional parameter which may take any value > 0               **
'**        (default 1) and causes the function to return the 'nth' best        **
'**         match (where 'n' is defined by 'Rank' parameter)                   **
'** If the 'Rank' match percentage < NFPercent (Default 5%), #N/A is returned. **
'** IndexNum is the column number of the entry in TableArray required to be    **
'** returned, as follows:                                                      **
'** If IndexNum > 0 and the 'Rank' percentage match is >= NFPercent            **
'**                 (Default 5%) the column entry indicated by IndexNum is     **
'**                 returned.                                                  **
'** if IndexNum = 0 and the 'Rank' percentage match is >= NFPercent            **
'**                 (Default 5%) the offset row (starting at 1) is returned.   **
'**                 This value can be used directly in the 'Index' function.   **
'**                                                                            **
'** Algorithm can take one of the following values:                            **
'** Algorithm = 1:                                                             **
'**     This algorithm is best suited for matching mis-spellings.              **
'**     For each character in 'String1', a search is performed on 'String2'.   **
'**     The search is deemed successful if a character is found in 'String2'   **
'**     within 3 characters of the current position.                           **
'**     A score is kept of matching characters which is returned as a          **
'**     percentage of the total possible score.                                **
'** Algorithm = 2:                                                             **
'**     This algorithm is best suited for matching sentences, or               **
'**     'firstname lastname' compared with 'lastname firstname' combinations   **
'**     A count of matching pairs, triplets, quadruplets etc. in 'String1' and **
'**     'String2' is returned as a percentage of the total possible.           **
'** Algorithm = 3: Both Algorithms 1 and 2 are performed.                      **
'** Algorithm = 4: Dan Ostrander's algorithm                                   **
'**                                                                            **
'** The following parameters allow matching by group, and only those values    **
'** which are in the group specified will be considered for matching.          **                  **
'** GroupColOffset                                                             **
'** This parameter specifies the offset column which contains the group values **
'** To trigger group matching, this must be a non-zero integer                 **
'** GroupValue                                                                 **
'** This parameter specifies the Group to be considered for matching           **
'********************************************************************************
Dim bWanted As Boolean
Dim lEndRow As Long

Dim rCur As Range
Dim rSearchRange As Range

Dim sngMinPercent As Single


Dim vCurValue As Variant
Dim wsTable As Worksheet

'--------------------------------------------------------------
'--    Validation                                            --
'--------------------------------------------------------------

LookupValue = LCase$(Application.Trim(LookupValue))

If IsMissing(NFPercent) Then
    sngMinPercent = 0.05
Else
    If (NFPercent <= 0) Or (NFPercent > 1) Then
        FuzzyVLookup = "*** 'NFPercent' must be a percentage > zero ***"
        Exit Function
    End If
    sngMinPercent = NFPercent
End If

If Rank < 1 Then
    FuzzyVLookup = "*** 'Rank' must be an integer > 0 ***"
    Exit Function
End If

Set wsTable = Sheets(TableArray.Parent.Name)

ReDim mudRankData(1 To Rank)

lEndRow = TableArray.Rows.Count
If VarType(TableArray.Cells(lEndRow, 1).Value) = vbEmpty Then
    lEndRow = TableArray.Cells(lEndRow, 1).End(xlUp).Row
End If
Set rSearchRange = Intersect(TableArray.Resize(, 1), wsTable.UsedRange)
If rSearchRange Is Nothing Then

    FuzzyVLookup = CVErr(xlErrNA)
    
Else


    '---------------
    '-- Main loop --
    '---------------
    
    If Len(GroupValue) <> 0 Then
        With rSearchRange.Offset(, GroupColOffset)
            For Each rCur In rSearchRange.Offset(, GroupColOffset)
                vCurValue = rCur.Value
                If VarType(vCurValue) = vbString Then
                    bWanted = LCase$(CStr(vCurValue)) = LCase$(CStr(GroupValue))
                Else
                    bWanted = Val(vCurValue) = Val(GroupValue)
                End If
                If bWanted Then
                    FuzzyVlookupMain LookupValue:=LookupValue, _
                                    TableArray:=rCur.Offset(, GroupColOffset * -1), _
                                    IndexNum:=IndexNum, _
                                    NFPercent:=NFPercent, _
                                    Rank:=Rank, _
                                    Algorithm:=Algorithm, _
                                    AdditionalCols:=AdditionalCols, _
                                    LookupColOffset:=LookupColOffset
                End If
            Next rCur
        End With
    Else
        For Each rCur In rSearchRange
            FuzzyVlookupMain LookupValue:=LookupValue, _
                            TableArray:=rCur, _
                            IndexNum:=IndexNum, _
                            NFPercent:=NFPercent, _
                            Rank:=Rank, _
                            Algorithm:=Algorithm, _
                            AdditionalCols:=AdditionalCols, _
                            LookupColOffset:=LookupColOffset
        Next rCur
    End If
    
    If mudRankData(Rank).Percentage < sngMinPercent Then
        '--------------------------------------
        '-- Return '#N/A' if below NFPercent --
        '--------------------------------------
        FuzzyVLookup = CVErr(xlErrNA)
    Else
        mlBestMatchPtr = mudRankData(Rank).Offset - TableArray.Cells(1, 1).Row + 1
        If IndexNum > 0 Then
            '-----------------------------------
            '-- Return column entry specified --
            '-----------------------------------
            FuzzyVLookup = TableArray.Cells(mlBestMatchPtr, IndexNum)
        Else
            '-----------------------
            '-- Return offset row --
            '-----------------------
            FuzzyVLookup = mlBestMatchPtr
        End If
    End If
    
End If          'If rSearchRange Is Nothing Then
End Function
Private Sub FuzzyVlookupMain(ByVal LookupValue As String, _
                                    ByVal TableArray As Range, _
                                    ByVal IndexNum As Integer, _
                                    Optional NFPercent As Single = 0.05, _
                                    Optional Rank As Integer = 1, _
                                    Optional Algorithm As Integer = 3, _
                                    Optional AdditionalCols As Integer = 0, _
                                    Optional LookupColOffset As Integer = 0)
Dim I As Integer
Dim intRankPtr As Integer
Dim intRankPtr1 As Integer
Dim strListString As String
Dim sngCurPercent As Single
Dim sngMinPercent As Single
Dim vCurValue As Variant

vCurValue = ""
For I = 0 To AdditionalCols
    vCurValue = vCurValue & CStr(TableArray.Offset(0, I + LookupColOffset).Value)
Next I
If VarType(vCurValue) = vbString Then
    strListString = LCase$(Application.Trim(vCurValue))
    
    '------------------------------------------------
    '-- Fuzzy match strings & get percentage match --
    '------------------------------------------------
    sngCurPercent = FuzzyPercent(String1:=LookupValue, _
                                 String2:=strListString, _
                                 Algorithm:=Algorithm, _
                                 Normalised:=True)
    
    If sngCurPercent >= sngMinPercent Then
        '---------------------------
        '-- Store in ranked array --
        '---------------------------
        For intRankPtr = 1 To Rank
            If sngCurPercent > mudRankData(intRankPtr).Percentage Then
                For intRankPtr1 = Rank To intRankPtr + 1 Step -1
                    With mudRankData(intRankPtr1)
                        .Offset = mudRankData(intRankPtr1 - 1).Offset
                        .Percentage = mudRankData(intRankPtr1 - 1).Percentage
                    End With
                Next intRankPtr1
                With mudRankData(intRankPtr)
                    .Offset = TableArray.Row
                    .Percentage = sngCurPercent
                End With
                Exit Sub
            End If
        Next intRankPtr
    End If
    
End If
End Sub

Parameters are: Lookupvalue, TableArray and NFPercent, all of which should match the FuzzyVLookup parameter values.
 
Upvote 0
Alan --- thanks for the help.
I've tried using your new code and came across a runtime error.

Set wsTable = Sheets(TableArray.Parent.Name)

I have two workbooks open, one with data to be matched and the other with data to be looked-up. I'm running your original macro on the sheets right now so I'm locked up.

The project we're working on is matching names and addresses, where the zip is exact. When I do find a match, I am interested in pulling more than one cell from the result ---- even the cell address. Is this possible?

thank you immensely for your code.
 
Upvote 0
Hi,welcome to the board!

The reason for the error is that the code does not work across workbooks.

Setting the 3rd parameter (IndexNum ) to zero will return the best match row. You can then use that in offset / index to obtain the required value without having to call the FuzzyVLookup function more than once.
 
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