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




3 Answers

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".


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:


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 preceeding 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
extract vba

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 matched pattern or replaced value in 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.




Expanding on patszim's answer for those in a rush.

  1. Open Excel workbook.
  2. Alt+F11 to open VBA/Macros window.
  3. Add reference to regex under Tools then References
  4. and selecting Microsoft VBScript Regular Expression 5.5
  5. Insert a new module (code needs to reside in the module otherwise it doesn't work).
  6. In the newly inserted module,
  7. add the following code:

    Function RegxFunc(strInput As String, regexPattern As String) As String
        Dim regEx As New RegExp
        With regEx
            .Global = True
            .MultiLine = True
            .IgnoreCase = False
            .pattern = regexPattern
        End With
    
        If regEx.Test(strInput) Then
            Set matches = regEx.Execute(strInput)
            RegxFunc = matches(0).Value
        Else
            RegxFunc = "not matched"
        End If
    End Function
    
  8. The regex pattern is placed in one of the cells and absolute referencing is used on it. Function will be tied to workbook that its created in.
    If there's a need for it to be used in different workbooks, store the function in Personal.XLSB




Here is a regex_subst() function. Examples:

=regex_subst("watermellon", "[aeiou]", "")
---> wtrmlln
=regex_subst("watermellon", "[^aeiou]", "")
---> aeeo

Here is the simplified code (simpler for me, anyway). I couldn't figure out how to build a suitable output pattern using the above to work like my examples:

Function regex_subst( _
     strInput As String _
   , matchPattern As String _
   , Optional ByVal replacePattern As String = "" _
) As Variant
    Dim inputRegexObj As New VBScript_RegExp_55.RegExp

    With inputRegexObj
        .Global = True
        .MultiLine = True
        .IgnoreCase = False
        .Pattern = matchPattern
    End With

    regex_subst = inputRegexObj.Replace(strInput, replacePattern)
End Function



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