String vs column - percent match - excel

Question

Trying to figure out a way to calculate the minimum percentage match when comparing a string to a column.
Example:
Column A Column B
Key Keylime
Key Chain Status
Serious
Extreme
Key
Where
Column A Column B Column C Column D
Key Temp 100% Key
Key Chain Status 66.7% Key Ch
Ten Key Ch 100% Tenure
Extreme
Key
Tenure
To expand on this:
Column A is the column with strings to individually match
Column B is the reference column
Column C provides the highest percent match the column A string has with any string in column B.
Column D provides the word from column B associated with the highest percent match
To expand on Column C - when looking at Key Chain - the highest match to any word it has in column B is for Key Ch where 6 out of the 9 characters (including space) of Key Chain match to give a percentage match of (6/9) = 66.7%
That being said, this isn't a deal breaker but it is something that sticks out. The logic above fails when there's no way to penalize for matches where you see an example like Ten occur. Where Ten has 3 out of 3 characters that match against Tenure giving it an inflated 100% match that I still can't think of a way to correct against.

Answer 1

This should work (i haven't tested it, currently on Linux). Call getStrMatch for each string.
Type StrMatch
Percent As Double
Word As String
End Type
Function getStrMatch(s As String, RefRange As Range) As StrMatch
Dim i As Long, ref_str As String
Dim BestMatch As StrMatch: BestMatch.Percent = -1
Dim match_pc As Double
With RefRange
For i = 1 to .Cells.Count
ref_str = .Cells(i).Value2
match_pc = getMatchPc(s, ref_str)
If match_pc > BestMatch.Percent Then
BestMatch.Percent = match_pc
BestMatch.Word = ref_str
End If
Next i
End With
getStrMatch = BestMatch
End Function
Function getMatchPc(s As String, ref_str As String) As Double
Dim s_len As Long: s_len = Len(s)
Dim ref_len As Long: ref_len = Len(ref_str)
Dim longer_len as Long
If s_len > ref_len Then longer_len = s_len Else longer_len = ref_len
Dim m As Long: m = 1
While m <= longer_len
If Mid(s, m, 1) <> Mid(ref_str, m, 1) Then Exit While
m = m + 1
Wend
getMatchPc = (m - 1.0) / longer_len
End Function
Note that you have to put this in a module or else declare Private Type and Private Function.
Also, if you're matching a lot of strings you probably should create a trie instead, as this is only doing naive string compares and each getStrMatch costs O(mn) where m is the size of the RefRange and n is the average ref_str length.