Results 1 to 4 of 4

Thread: Thinking About Using VBA's IsNumeric Function? Read this first.

  1. #1
    Forum Guru Rick Rothstein's Avatar
    Join Date
    Feb 2012
    Posts
    662
    Rep Power
    13

    Thinking About Using VBA's IsNumeric Function? Read this first.

    I have posted the following many times over the last 10 years or so in responding to old newsgroup and current forum questions. I decided to post it here for all to see.

    I usually try and steer people away from using IsNumeric to "proof" supposedly numeric text. Consider this (also see note below):

    Code:
    ReturnValue = IsNumeric("($1,23,,3.4,,,5,,D56$)$$$$$$$")
    Most people would not expect THAT to return True. IsNumeric has some "flaws" in what it considers a proper number and what most programmers are looking for.

    I had a short tip published by Pinnacle Publishing in their Visual Basic Developer magazine that covered some of these flaws. Originally, the tip was free to view but is now viewable only by subscribers.. Basically, it said that IsNumeric returned True for things like -- currency symbols being located in front or in back of the number as shown in my example (also applies to plus, minus and blanks too); numbers surrounded by parentheses as shown in my example (some people use these to mark negative numbers); numbers containing any number of commas before a decimal point as shown in my example; numbers in scientific notation (a number followed by an upper or lower case "D" or "E", followed by a number equal to or less than 307 -- the maximum power of 10 in VB); and Octal/Hexadecimal numbers (&H for Hexadecimal, &O or just & in front of the number for Octal).

    NOTE:
    ======
    In the above example and in the referenced tip, I refer to $ signs and commas and dots -- these were meant to refer to your currency, thousands separator and decimal point symbols as defined in your local settings -- substitute your local regional symbols for these if appropriate.

    As for your question about checking numbers, here are two functions that I have posted in the past for similar questions..... one is for digits only and the other is for "regular" numbers (the code is simple enough that it can be pulled from the function "housing" and used directly inside your own code):

    Code:
    Function IsDigitsOnly(Value As String) As Boolean
        IsDigitsOnly = Len(Value) > 0 And Not Value Like "*[!0-9]*"
    End Function
    
    Function IsNumber(ByVal Value As String) As Boolean
        '   Leave the next statement out if you don't
        '   want to provide for plus/minus signs
        If Value Like "[+-]*" Then Value = Mid$(Value, 2)
        IsNumber = Not Value Like "*[!0-9.]*" And Not Value Like "*.*.*" And Len(Value) > 0 And Value <> "."
    End Function
    Here are revisions to the above functions that deal with the local settings for decimal points (and thousand's separators) that are different than used in the US (this code works in the US too, of course).

    Code:
    Function IsNumber(ByVal Value As String) As Boolean
      Dim DP As String
      '   Get local setting for decimal point
      DP = Format$(0, ".")
      '   Leave the next statement out if you don't
      '   want to provide for plus/minus signs
      If Value Like "[+-]*" Then Value = Mid$(Value, 2)
      IsNumber = Not Value Like "*[!0-9" & DP & "]*" And Not Value Like "*" & _
                 DP & "*" & DP & "*" And Len(Value) > 0 And Value <> DP
    End Function
    I'm not as concerned by the rejection of entries that include one or more thousand's separators, but we can handle this if we don't insist on the thousand's separator being located in the correct positions (in other words, we'll allow the user to include them for their own purposes... we'll just tolerate their presence).

    Code:
    Function IsNumber(ByVal Value As String) As Boolean
      Dim DP As String
      Dim TS As String
      '   Get local setting for decimal point
      DP = Format$(0, ".")
      '   Get local setting for thousand's separator
      '   and eliminate them. Remove the next two lines
      '   if you don't want your users being able to
      '   type in the thousands separator at all.
      TS = Mid$(Format$(1000, "#,###"), 2, 1)
      Value = Replace$(Value, TS, "")
      '   Leave the next statement out if you don't
      '   want to provide for plus/minus signs
      If Value Like "[+-]*" Then Value = Mid$(Value, 2)
      IsNumber = Not Value Like "*[!0-9" & DP & "]*" And Not Value Like "*" & _
                 DP & "*" & DP & "*" And Len(Value) > 0 And Value <> DP
    End Function
    Last edited by Rick Rothstein; 08-15-2021 at 08:04 AM.

  2. #2
    Fuhrer, Vierte Reich DocAElstein's Avatar
    Join Date
    Aug 2014
    Posts
    9,422
    Rep Power
    10

    Application.IsNumber( ) is an alternative to IsNumeric( ))

    Thanks for these ideas, Rick. - I just thought I would mention that, as I passed this Blog post on just now, I saw in that Thread something that might be worth mentioning here in passing, which is that Hans offered an Excel Worksheet function alternative, Application.IsNumber( ) , which seems more likely to give results closer to what most people would expect.
    If I understand correctly the main difference between the two functions can be thought of approximately as
    IsNumeric( ) is True if it thinks it can convert the given text into a number, whereas
    Application.IsNumber( ) is more likely to be True only if the passed thing looks like a number, ( it won't , for example . convert a text into a number, even anything simple like "2" )

    That is just an approximate conclusion as I have not investigated thoroughly both functions yet…

    The intelligence behind IsNumeric( ) is perhaps a different one to ours, and perhaps as a compromise for efficiency does not thoroughly check for correctness, but rather looks for some allowed characters that might be used in some number formats,
    ( and it allows a text that has a number format,
    ( whereas Application.IsNumber( ) doesn’t: For example Application.IsNumber("1") is false because "1" is text )
    IsNumeric("1") is True)

    Alan

    ( Edit P.S. I geuss you will need to be in Excel or else load the Excel library in order to use Application.IsNumber( ) )
    Last edited by DocAElstein; 03-25-2021 at 11:26 PM. Reason: Edit P.S. I geuss you will need to be in Excel or else load the Excel library in order to use Application.IsNumber( )
    ….If you are my competitor, I will try all I can to beat you. But if I do, I will not belittle you. I will Salute you, because without you, I am nothing.
    If you are my enemy, we will try to kick the fucking shit out of you…..
    Winston Churchill, 1939
    Save your Forum..._
    _...KILL A MODERATOR!!

  3. #3
    Forum Guru Rick Rothstein's Avatar
    Join Date
    Feb 2012
    Posts
    662
    Rep Power
    13
    Since you are doing this in VBA, the question of how you convert the text to a number becomes important. Consider these...

    MsgBox Application.IsNumber(Val("OCT1"))

    MsgBox Application.IsNumber(Val("12E34"))

    I still like crafting (customizing) a solution using the Like operator myself.


    https://www.youtube.com/channel/UCnxwq2aGJRbjOo_MO54oaHA
    https://www.youtube.com/watch?v=jTmVtPHtiTg&lc=Ugy_RiNN_kAqUvZ8W994AaABAg
    https://www.youtube.com/watch?v=QjEWAJ3d-jw&lc=UgxJLVpwY8fIla7G-pN4AaABAg.9BLeCWVhxdG9wgNsaS3Lp1
    https://www.youtube.com/watch?v=QjEWAJ3d-jw&lc=UgxJLVpwY8fIla7G-pN4AaABAg.9BLeCWVhxdG9wgR1EPUkhw
    https://www.youtube.com/watch?v=QjEWAJ3d-jw&lc=UgxJLVpwY8fIla7G-pN4AaABAg.9BLeCWVhxdG9wgNe_XC-jK
    https://www.youtube.com/watch?v=QjEWAJ3d-jw&lc=UgxJLVpwY8fIla7G-pN4AaABAg.9BLeCWVhxdG9wgNPOdiDuv
    https://www.youtube.com/watch?v=QjEWAJ3d-jw&lc=UgxJLVpwY8fIla7G-pN4AaABAg.9BLeCWVhxdG9wgN7AC7wAc
    https://www.youtube.com/watch?v=bs-urI_o8jo&lc=UgyBACXgNY4j_cHgH5J4AaABAg.9oTkVdzfqfm 9wlhQrYJP3M
    https://www.youtube.com/watch?v=bs-urI_o8jo&lc=UgxYgiEZuS9I3xkjJv54AaABAg
    https://www.youtube.com/watch?v=DVFFApHzYVk&lc=Ugyi578yhj9zShmhuPl4AaABAg
    https://www.youtube.com/watch?v=GqzeFYWjTxI&lc=UgxvxlnuTRWiV6MUZB14AaABAg
    https://www.youtube.com/watch?v=_8i1fVEi5WY&lc=Ugz0ptwE5J-2CpX4Lzh4AaABAg
    https://www.youtube.com/watch?v=0ltJS7uHfK4&lc=UgxoHAw8RwR7VmyVBUt4AaABAg. 9C-br0lEl8V9xI0_6pCaR9
    https://www.youtube.com/watch?v=0ltJS7uHfK4&lc=Ugz5DDCMqmHLeEjUU8t4AaABAg. 9bl7m03Onql9xI-ar3Z0ME
    https://www.youtube.com/watch?v=0ltJS7uHfK4&lc=UgxYnpd9leriPmc8rPd4AaABAg. 9gdrYDocLIm9xI-2ZpVF-q
    https://www.youtube.com/watch?v=0ltJS7uHfK4&lc=UgyjoPLjNeIAOMVH_u94AaABAg. 9id_Q3FO8Lp9xHyeYSuv1I
    https://www.reddit.com/r/windowsxp/comments/pexq9q/comment/k81ybvj/?utm_source=reddit&utm_medium=web2x&context=3
    https://www.youtube.com/watch?v=bs-urI_o8jo&lc=UgxYgiEZuS9I3xkjJv54AaABAg
    https://www.youtube.com/watch?v=bs-urI_o8jo&lc=UgyBACXgNY4j_cHgH5J4AaABAg.9oTkVdzfqfm 9wlhQrYJP3M
    ttps://www.youtube.com/watch?v=LP9fz2DCMBE
    https://www.youtube.com/watch?v=LP9fz2DCMBE&lc=UgzbPgJUMCztIOQDym14AaABAg
    https://www.youtube.com/watch?v=LP9fz2DCMBE&lc=UgzbPgJUMCztIOQDym14AaABAg. 9wdo_rWgxSH9wdpcYqrvp8
    ttps://www.youtube.com/watch?v=bFxnXH4-L1A
    https://www.youtube.com/watch?v=bFxnXH4-L1A&lc=UgxuODisjo6cvom7O-B4AaABAg.9w_AeS3JiK09wdi2XviwLG
    https://www.youtube.com/watch?v=bFxnXH4-L1A&lc=UgxBU39bTptFznDC1PJ4AaABAg
    ttps://www.youtube.com/watch?v=GqzeFYWjTxI
    https://www.youtube.com/watch?v=GqzeFYWjTxI&lc=UgwJnJDJ5JT8hFvibt14AaABAg
    https://www.youtube.com/channel/UCnxwq2aGJRbjOo_MO54oaHA
    Last edited by DocAElstein; 11-30-2023 at 03:12 PM.

  4. #4
    Fuhrer, Vierte Reich DocAElstein's Avatar
    Join Date
    Aug 2014
    Posts
    9,422
    Rep Power
    10
    Hello Rick

    I personally generally prefer to use some basic VBA and/or VB string manipulation stuff in a User Defined Function, although I suppose, theoretically at least, an in built function might be more efficient sometimes, assuming the person who developed it knew what he was doing.
    ( A UDF I would also prefer to develop in an older Office version, using more fundamental things, as it’s a good chance then of always working also in newer office versions.
    I am personally rather annoyed by Microsoft thinking that development is introducing new Functions, which then give backward compatibility problems, or coding no longer works sometimes as it did
    …. )

    I also like that use of the Like operator. I have not used that Like much. I should get clued up on it. It looks like a useful extra tool to have when doing string manipulation and analysis.
    ( Often in the past I have got rather confused with other “Wild” card thing syntaxes , like in Find and Replace strings, Reg Ex and co. etc.
    But a quick google just now on the Like operator reveals that its not so complicated, and should not take long to learn. ( Maybe a post on the Like operator could be a useful addition at excelfox tips for one of us to do sometime
    ) )




    I see that the Val function is not without its "gotchas" either….
    Application.IsNumber(Val("OCT1")) is perhaps showing us another Val "gotcha" , - Val when it doesn’t manage to return as a number, .. actually does return as a number - the number 0
    Clearly that might be inconvenient some times !!!
    In that specific example you gave, people might have thought that the Val had returned the date number. That would have been my initial guess, after seeing that MsgBox Application.IsNumber(Val("OCT1")) gave True
    I see now that its doing that because Val("OCT1") is giving me the number 0 !!! - its doing that because it did not manage to return a number from the string "OCT1"
    ValReturns0.JPG

    Alan

    https://www.youtube.com/channel/UCnxwq2aGJRbjOo_MO54oaHA
    https://www.youtube.com/@alanelston2330
    https://www.youtube.com/watch?v=yXaYszT11CA&lc=UgxEjo0Di9-9cnl8UnZ4AaABAg.9XYLEH1OwDIA35HNIei0z-
    https://eileenslounge.com/viewtopic.php?p=316154#p316154
    https://www.youtube.com/watch?v=TW3l7PkSPD4&lc=UgwAL_Jrv7yg7WWC8x14AaABAg
    https://teylyn.com/2017/03/21/dollarsigns/#comment-191
    https://eileenslounge.com/viewtopic.php?p=317050#p317050
    https://eileenslounge.com/viewtopic.php?f=27&t=40953&p=316854#p316854
    https://www.eileenslounge.com/viewtopic.php?v=27&t=40953&p=316875#p316875
    https://eileenslounge.com/viewtopic.php?p=316057#p316057
    https://eileenslounge.com/viewtopic.php?p=316705#p316705
    https://eileenslounge.com/viewtopic.php?p=316704#p316704
    https://eileenslounge.com/viewtopic.php?p=176255#p176255
    https://eileenslounge.com/viewtopic.php?f=27&t=40919&p=316597#p316597
    https://eileenslounge.com/viewtopic.php?p=316412#p316412
    https://eileenslounge.com/viewtopic.php?p=316254#p316254
    https://eileenslounge.com/viewtopic.php?p=316280#p316280
    https://eileenslounge.com/viewtopic.php?p=315915#p315915
    https://eileenslounge.com/viewtopic.php?p=315512#p315512
    https://eileenslounge.com/viewtopic.php?p=315744#p315744
    https://www.youtube.com/channel/UCnxwq2aGJRbjOo_MO54oaHA
    Last edited by DocAElstein; 05-08-2024 at 02:29 AM.
    ….If you are my competitor, I will try all I can to beat you. But if I do, I will not belittle you. I will Salute you, because without you, I am nothing.
    If you are my enemy, we will try to kick the fucking shit out of you…..
    Winston Churchill, 1939
    Save your Forum..._
    _...KILL A MODERATOR!!

Similar Threads

  1. UDF (user defined function) replacement for Excel's DATEDIF function
    By Rick Rothstein in forum Rick Rothstein's Corner
    Replies: 21
    Last Post: 03-07-2015, 09:47 PM
  2. Excel 2010 hide Read Only messages
    By DAUPVVO in forum Excel Help
    Replies: 1
    Last Post: 03-19-2014, 07:51 AM
  3. How To Make A Workbook Read-Only
    By Transformer in forum Tips, Tricks & Downloads (No Questions)
    Replies: 0
    Last Post: 07-16-2013, 07:28 AM
  4. Read/write very large xl2007 files
    By Rasm in forum Excel Help
    Replies: 3
    Last Post: 04-07-2012, 05:28 AM
  5. Replies: 2
    Last Post: 12-12-2011, 01:51 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •