How to use Regular Expressions (Regex) in Microsoft Excel both in-cell and loops

ghz 1years ago ⋅ 2112 views

Question

How can I use regular expressions in Excel and take advantage of Excel's powerful grid-like setup for data manipulation?

  • In-cell function to return a matched pattern or replaced value in a string.
  • Sub to loop through a column of data and extract matches to adjacent cells.
  • What setup is necessary?
  • What are Excel's special characters for Regular expressions?

I understand Regex is not ideal for many situations (To use or not to use regular expressions?) since excel can use Left, Mid, Right, Instr type commands for similar manipulations.

Answer

Regular expressions are used for Pattern Matching.

To use in Excel follow these steps:

Step 1 : Add VBA reference to "Microsoft VBScript Regular Expressions 5.5"

  • Select "Developer" tab (I don't have this tab what do I do?)
  • Select "Visual Basic" icon from 'Code' ribbon section
  • In "Microsoft Visual Basic for Applications" window select "Tools" from the top menu.
  • Select "References"
  • Check the box next to "Microsoft VBScript Regular Expressions 5.5" to include in your workbook.
  • Click "OK"

Step 2 : Define your pattern

Basic definitions:

- Range.

  • E.g. a-z matches an lower case letters from a to z
  • E.g. 0-5 matches any number from 0 to 5

[] Match exactly one of the objects inside these brackets.

  • E.g. [a] matches the letter a
  • E.g. [abc] matches a single letter which can be a, b or c
  • E.g. [a-z] matches any single lower case letter of the alphabet.

() Groups different matches for return purposes. See examples below.

{} Multiplier for repeated copies of pattern defined before it.

  • E.g. [a]{2} matches two consecutive lower case letter a: aa
  • E.g. [a]{1,3} matches at least one and up to three lower case letter a, aa, aaa

+ Match at least one, or more, of the pattern defined before it.

  • E.g. a+ will match consecutive a's a, aa, aaa, and so on

? Match zero or one of the pattern defined before it.

  • E.g. Pattern may or may not be present but can only be matched one time.
  • E.g. [a-z]? matches empty string or any single lower case letter.

* Match zero or more of the pattern defined before it.

  • E.g. Wildcard for pattern that may or may not be present.
  • E.g. [a-z]* matches empty string or string of lower case letters.

. Matches any character except newline \n

  • E.g. a. Matches a two character string starting with a and ending with anything except \n

| OR operator

  • E.g. a|b means either a or b can be matched.
  • E.g. red|white|orange matches exactly one of the colors.

^ NOT operator

  • E.g. [^0-9] character can not contain a number
  • E.g. [^aA] character can not be lower case a or upper case A

\ Escapes special character that follows (overrides above behavior)

  • E.g. \., \\, \(, \?, \$, \^

Anchoring Patterns:

^ Match must occur at start of string

  • E.g. ^a First character must be lower case letter a
  • E.g. ^[0-9] First character must be a number.

$ Match must occur at end of string

  • E.g. a$ Last character must be lower case letter a

Precedence table:

Order  Name                Representation
1      Parentheses         ( )
2      Multipliers         ? + * {m,n} {m, n}?
3      Sequence & Anchors  abc ^ $
4      Alternation         |

Predefined Character Abbreviations:

abr    same as       meaning
\d     [0-9]         Any single digit
\D     [^0-9]        Any single character that's not a digit
\w     [a-zA-Z0-9_]  Any word character
\W     [^a-zA-Z0-9_] Any non-word character
\s     [ \r\t\n\f]   Any space character
\S     [^ \r\t\n\f]  Any non-space character
\n     [\n]          New line

Example 1 : Run as macro

The following example macro looks at the value in cell A1 to see if the first 1 or 2 characters are digits. If so, they are removed and the rest of the string is displayed. If not, then a box appears telling you that no match is found. Cell A1 values of 12abc will return abc, value of 1abc will return abc, value of abc123 will return "Not Matched" because the digits were not at the start of the string.

Private Sub simpleRegex()
    Dim strPattern As String: strPattern = "^[0-9]{1,2}"
    Dim strReplace As String: strReplace = ""
    Dim regEx As New RegExp
    Dim strInput As String
    Dim Myrange As Range
    
    Set Myrange = ActiveSheet.Range("A1")
    
    If strPattern <> "" Then
        strInput = Myrange.Value
        
        With regEx
            .Global = True
            .MultiLine = True
            .IgnoreCase = False
            .Pattern = strPattern
        End With
        
        If regEx.Test(strInput) Then
            MsgBox (regEx.Replace(strInput, strReplace))
        Else
            MsgBox ("Not matched")
        End If
    End If
End Sub

Example 2 : Run as an in-cell function

This example is the same as example 1 but is setup to run as an in-cell function. To use, change the code to this:

Function simpleCellRegex(Myrange As Range) As String
    Dim regEx As New RegExp
    Dim strPattern As String
    Dim strInput As String
    Dim strReplace As String
    Dim strOutput As String
    
    
    strPattern = "^[0-9]{1,3}"
    
    If strPattern <> "" Then
        strInput = Myrange.Value
        strReplace = ""
        
        With regEx
            .Global = True
            .MultiLine = True
            .IgnoreCase = False
            .Pattern = strPattern
        End With
        
        If regEx.test(strInput) Then
            simpleCellRegex = regEx.Replace(strInput, strReplace)
        Else
            simpleCellRegex = "Not matched"
        End If
    End If
End Function

Place your strings ("12abc") in cell A1. Enter this formula =simpleCellRegex(A1) in cell B1 and the result will be "abc".

results image

Example 3 : Loop Through Range

This example is the same as example 1 but loops through a range of cells.

Private Sub simpleRegex()
    Dim strPattern As String: strPattern = "^[0-9]{1,2}"
    Dim strReplace As String: strReplace = ""
    Dim regEx As New RegExp
    Dim strInput As String
    Dim Myrange As Range
    
    Set Myrange = ActiveSheet.Range("A1:A5")
    
    For Each cell In Myrange
        If strPattern <> "" Then
            strInput = cell.Value
            
            With regEx
                .Global = True
                .MultiLine = True
                .IgnoreCase = False
                .Pattern = strPattern
            End With
            
            If regEx.Test(strInput) Then
                MsgBox (regEx.Replace(strInput, strReplace))
            Else
                MsgBox ("Not matched")
            End If
        End If
    Next
End Sub

Example 4 : Splitting apart different patterns

This example loops through a range (A1, A2 & A3) and looks for a string starting with three digits followed by a single alpha character and then 4 numeric digits. The output splits apart the pattern matches into adjacent cells by using the (). $1 represents the first pattern matched within the first set of ().

Private Sub splitUpRegexPattern()
    Dim regEx As New RegExp
    Dim strPattern As String
    Dim strInput As String
    Dim Myrange As Range
    
    Set Myrange = ActiveSheet.Range("A1:A3")
    
    For Each C In Myrange
        strPattern = "(^[0-9]{3})([a-zA-Z])([0-9]{4})"
        
        If strPattern <> "" Then
            strInput = C.Value
            
            With regEx
                .Global = True
                .MultiLine = True
                .IgnoreCase = False
                .Pattern = strPattern
            End With
            
            If regEx.test(strInput) Then
                C.Offset(0, 1) = regEx.Replace(strInput, "$1")
                C.Offset(0, 2) = regEx.Replace(strInput, "$2")
                C.Offset(0, 3) = regEx.Replace(strInput, "$3")
            Else
                C.Offset(0, 1) = "(Not matched)"
            End If
        End If
    Next
End Sub

Results:

results image

Additional Pattern Examples

String   Regex Pattern                  Explanation
a1aaa    [a-zA-Z][0-9][a-zA-Z]{3}       Single alpha, single digit, three alpha characters
a1aaa    [a-zA-Z]?[0-9][a-zA-Z]{3}      May or may not have preceding alpha character
a1aaa    [a-zA-Z][0-9][a-zA-Z]{0,3}     Single alpha, single digit, 0 to 3 alpha characters
a1aaa    [a-zA-Z][0-9][a-zA-Z]*         Single alpha, single digit, followed by any number of alpha characters

</i8>    \<\/[a-zA-Z][0-9]\>            Exact non-word character except any single alpha followed by any single digit
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