I have been researching fuzzy match / search algorithms across the internet. I have tried a couple of solutions.
The only that gave somewhat accurate results was from Mr. Excel (http://www.mrexcel.com/pc07.shtml). The problem with this method is the order or relative position of characters in the words and the order of the words themselves had no effect on the results.
I would like to get better results based on the relative word position as well as the order of the letters per word.
Function FuzzyMatchByWord(ByVal lsPhrase1 As String, ByVal lsPhrase2 As String, Optional lbStripVowels As Boolean = False, Optional lbDiscardExtra As Boolean = False) As Double
'
' Compare two phrases and return a similarity value (between 0 and 100).
'
' Arguments:
'
' 1. Phrase1 String; any text string
' 2. Phrase2 String; any text string
' 3. StripVowels Optional to strip all vowels from the phrases
' 4. DiscardExtra Optional to discard any unmatched words
'
'local variables
Dim lsWord1() As String
Dim lsWord2() As String
Dim ldMatch() As Double
Dim ldCur As Double
Dim ldMax As Double
Dim liCnt1 As Integer
Dim liCnt2 As Integer
Dim liCnt3 As Integer
Dim lbMatched() As Boolean
Dim lsNew As String
Dim lsChr As String
Dim lsKeep As String
'set default value as failure
FuzzyMatchByWord = 0
'create list of characters to keep
lsKeep = "BCDFGHJKLMNPQRSTVWXYZ0123456789 "
If Not lbStripVowels Then
lsKeep = lsKeep & "AEIOU"
End If
'clean up phrases by stripping undesired characters
'phrase1
lsPhrase1 = Trim$(UCase$(lsPhrase1))
lsNew = ""
For liCnt1 = 1 To Len(lsPhrase1)
lsChr = Mid$(lsPhrase1, liCnt1, 1)
If InStr(lsKeep, lsChr) <> 0 Then
lsNew = lsNew & lsChr
End If
Next
lsPhrase1 = lsNew
lsPhrase1 = Replace(lsPhrase1, " ", " ")
lsWord1 = Split(lsPhrase1, " ")
If UBound(lsWord1) = -1 Then
Exit Function
End If
ReDim ldMatch(UBound(lsWord1))
'phrase2
lsPhrase2 = Trim$(UCase$(lsPhrase2))
lsNew = ""
For liCnt1 = 1 To Len(lsPhrase2)
lsChr = Mid$(lsPhrase2, liCnt1, 1)
If InStr(lsKeep, lsChr) <> 0 Then
lsNew = lsNew & lsChr
End If
Next
lsPhrase2 = lsNew
lsPhrase2 = Replace(lsPhrase2, " ", " ")
lsWord2 = Split(lsPhrase2, " ")
If UBound(lsWord2) = -1 Then
Exit Function
End If
ReDim lbMatched(UBound(lsWord2))
'exit if empty
If Trim$(lsPhrase1) = "" Or Trim$(lsPhrase2) = "" Then
Exit Function
End If
'compare words in each phrase
For liCnt1 = 0 To UBound(lsWord1)
ldMax = 0
For liCnt2 = 0 To UBound(lsWord2)
If Not lbMatched(liCnt2) Then
ldCur = FuzzyMatch(lsWord1(liCnt1), lsWord2(liCnt2))
If ldCur > ldMax Then
liCnt3 = liCnt2
ldMax = ldCur
End If
End If
Next
lbMatched(liCnt3) = True
ldMatch(liCnt1) = ldMax
Next
'discard extra words
ldMax = 0
For liCnt1 = 0 To UBound(ldMatch)
ldMax = ldMax + ldMatch(liCnt1)
Next
If lbDiscardExtra Then
liCnt2 = 0
For liCnt1 = 0 To UBound(lbMatched)
If lbMatched(liCnt1) Then
liCnt2 = liCnt2 + 1
End If
Next
Else
liCnt2 = UBound(lsWord2) + 1
End If
'return overall similarity
FuzzyMatchByWord = 100 * (ldMax / liCnt2)
End Function
Function FuzzyMatch(Fstr As String, Sstr As String) As Double
'
' Code sourced from: http://www.mrexcel.com/pc07.shtml
' Credited to: Ed Acosta
' Modified: Joe Stanton
'
Dim L, L1, L2, M, SC, T, R As Integer
L = 0
M = 0
SC = 1
L1 = Len(Fstr)
L2 = Len(Sstr)
Do While L < L1
L = L + 1
For T = SC To L1
If Mid$(Sstr, L, 1) = Mid$(Fstr, T, 1) Then
M = M + 1
SC = T
T = L1 + 1
End If
Next T
Loop
If L1 = 0 Then
FuzzyMatch = 0
Else
FuzzyMatch = M / L1
End If
End Function
I am trying to compare account descriptions from a trial balance to a list of 30,000 past account descriptions and I want to find the 5 top results per account.
To give you an example:
Debug.Print FuzzyMatchByWord("Cash and Cash Equivalents", "Bank and Cash")
Debug.Print FuzzyMatchByWord("Cash and Cash Equivalents", "Cash and Bank")
Debug.Print FuzzyMatchByWord("Cash and Cash Equivalents", "Shack sequential")
Debug.Print FuzzyMatchByWord("Cash and Cash Equivalents", "Sequential shack")
Returns:
75
75
37.5
37.5
I would want the relative placement of a word in a phrase to count more towards the score and I would also prefer the order of the letters have a bigger impact. Sequential shack should not have scored that high compared to Cash and Cash Equivalents.
When comparing Strings I usually use the Levenshtein-Distance. You can find an implementation of the algorithm here. You can extend the function by the Ratio, which is a pretty good indicator for measuring how "close" two strings are.
Function levenshtein(a As String, b As String, Optional ratio As Boolean) As Double
Dim i As Long, j As Long, cost As Long
Dim d() As Long
Dim min1 As Long, min2 As Long, min3 As Long
If Len(a) = 0 Then
levenshtein = Len(b)
Exit Function
End If
If Len(b) = 0 Then
levenshtein = Len(a)
Exit Function
End If
ReDim d(Len(a), Len(b))
For i = 0 To Len(a)
d(i, 0) = i
Next
For j = 0 To Len(b)
d(0, j) = j
Next
For i = 1 To Len(a)
For j = 1 To Len(b)
If Mid(a, i, 1) = Mid(b, j, 1) Then
cost = 0
Else
cost = 1
End If
min1 = (d(i - 1, j) + 1)
min2 = (d(i, j - 1) + 1)
min3 = (d(i - 1, j - 1) + cost)
d(i, j) = Application.WorksheetFunction.Min(min1, min2, min3)
Next
Next
If ratio Then
levenshtein = (Len(a) + Len(b) - d(Len(a), Len(b))) / (Len(a) + Len(b))
Else
levenshtein = d(Len(a), Len(b))
End If
End Function
For your examples:
Debug.Print levenshtein("Cash and Cash Equivalents", "Bank and Cash", True)
Debug.Print levenshtein("Cash and Cash Equivalents", "Cash and Bank", True)
Debug.Print levenshtein("Cash and Cash Equivalents", "Shack sequential", True)
Debug.Print levenshtein("Cash and Cash Equivalents", "Sequential shack", True)
Returns:
0.605263157894737
0.631578947368421
0.560975609756098
0.48780487804878
EDIT
I guess the String-Comparisons are slowing things down a lot. One way to speed this up, is to convert the String into a Byte-Array and compare numeric values. This could be done like this:
Function levenshtein(a As String, b As String, Optional ratio As Boolean) As Double
Dim i As Long, j As Long
Dim k As Long, l As Long
Dim cost As Long
Dim d() As Long
Dim min1 As Long, min2 As Long, min3 As Long
Dim aByte1() As Byte, aByte2() As Byte
If Len(a) = 0 Then
levenshtein = Len(b)
Exit Function
End If
If Len(b) = 0 Then
levenshtein = Len(a)
Exit Function
End If
ReDim d(Len(a), Len(b))
For i = 0 To Len(a)
d(i, 0) = i
Next
For j = 0 To Len(b)
d(0, j) = j
Next
aByte1 = a
aByte2 = b
For i = 0 To UBound(aByte1, 1) Step 2
k = Int(i / 2) + 1
For j = 0 To UBound(aByte2, 1) Step 2
If aByte1(i) = aByte2(j) Then
cost = 0
Else
cost = 1
End If
l = Int(j / 2) + 1
min1 = (d(k - 1, l) + 1)
min2 = (d(k, l - 1) + 1)
min3 = (d(k - 1, l - 1) + cost)
d(k, l) = Application.WorksheetFunction.Min(min1, min2, min3)
Next
Next
If ratio Then
levenshtein = (Len(a) + Len(b) - d(Len(a), Len(b))) / (Len(a) + Len(b))
Else
levenshtein = d(Len(a), Len(b))
End If
End Function