Comments on: Summing the Digits of a Number

By: Rick Rothstein (MVP - Excel)

Rick Rothstein (MVP - Excel) — Mon, 16 Nov 2009 17:30:00 +0000

I wrote my original function more as an interesting case because it was a one-liner solution. If you want to go to multiple lines and, especially, a loop solution, then I would use the code Charles Williams posted earlier… the Byte array method would be among the fastest possible loop solutions that could be constructed.

By: hans schraven

hans schraven — Mon, 16 Nov 2009 17:13:00 +0000

Rick,

to avoid limits and 'impossible' tests:

Function SumDigits2(S As Variant) As Long
c1 = Replace(String(29, "+"), "+", "+0")
For j = 1 To Len(Replace(S, ".", "")) Step 29
SumDigits2 = SumDigits2 + Evaluate(Format(Mid(Replace(S, ".", ""), j, 29), c1))
Next
End Function

By: Rick Rothstein (MVP - Excel)

Rick Rothstein (MVP - Excel) — Mon, 16 Nov 2009 16:17:00 +0000

What! I did it again!! Okay, I changed the test so that I can't screw it up again ;-)

Function SumDigits2(S As Variant) As Long
If Len(S) Then SumDigits2 = Evaluate(Format(Replace(S, ".", ""), Replace(String(29, "x"), "x", "+0")))
End Function

By: Rick Rothstein (MVP - Excel)

Rick Rothstein (MVP - Excel) — Mon, 16 Nov 2009 16:14:00 +0000

Arrgh! I did it again... I forgot about the "not equal" sign problem...

Function SumDigits2(S As Variant) As Long
If S "" Then SumDigits2 = Evaluate(Format(Replace(S, ".", ""), Replace(String(29, "x"), "x", "+0")))
End Function

By: Rick Rothstein (MVP - Excel)

Rick Rothstein (MVP - Excel) — Mon, 16 Nov 2009 16:12:00 +0000

Hans,

Your function will not be able to handle more than 29 total (text) digits because of a limitation in the Format function... it appears to use the Decimal sub-type of the Variant data type to process its first argument and the Decimal sub-type is limited to a maximum of 29 digits total digits providing there is no decimal point (which is the reason for the first Replace function call). For example, try this macro out with your function and you will see the problem (displayed in the Immediate Window)...

Sub test()
Dim X As Long, TestNumber As String
For X = 1 To 3
TestNumber = "123456789012345678901234567" & Mid("890", 1, X)
Debug.Print "Sum " & TestNumber & " digits is " & SumDigits2(TestNumber)
Next
End Sub

The first two digit sums will be correct but the third one (where only a zero is being affixed to the end of the second one) will be obviously incorrect. However, I do note your elimination of the concatenation of the leading zero in favor of including it inside the second Replace function call is a good way to simplify the function further...

Function SumDigits2(S As Variant) As Long
If S "" Then SumDigits2 = Evaluate(Format(Replace(S, ".", ""), Replace(String(29, "x"), "x", "+0")))
End Function

By: hans schraven

hans schraven — Mon, 16 Nov 2009 12:12:00 +0000

Function SumDigits2(S As Variant) As Long
If S NEQ "" Then SumDigits2 = Evaluate(Format(Replace(S, ".", ""), Replace(string(len(s),"x"), "x", "+0")))
End Function

By: Rick Rothstein (MVP - Excel)

Rick Rothstein (MVP - Excel) — Sun, 15 Nov 2009 22:59:00 +0000

Let’s try that formula again, this time using .ne. in place of the “not equal” sign (less than symbol followed by greater than symbol) that the Comment Processor “ate” (so if copy/pasting this, make the substition back to the “not equal” sign)…

Function SumDigits2(S As Variant) As Long
If S .ne. “” Then SumDigits2 = Evaluate(Format(Replace(S, “.”, “”), “0? & Replace(String(28, “x”), “x”, “+0?)))
End Function

By: Rick Rothstein (MVP - Excel)

Rick Rothstein (MVP - Excel) — Sun, 15 Nov 2009 22:55:00 +0000

If you are willing to accept an error being generated if a cell does not contain a real number (whether as text or as an actual number), 12AB34 as an example, and if you textual numbers are no more than 29 significant digits long, then this one-liner UDF should work...

Function SumDigits2(S As Variant) As Long
If S "" Then SumDigits2 = Evaluate(Format(Replace(S, ".", ""), "0? & Replace(String(28, "x"), "x", "+0?)))
End Function

By: Tushar Mehta

Tushar Mehta — Sat, 10 Oct 2009 18:06:00 +0000

Lori: That’s slick. It works with positive and negative numbers, with an empty cell, and with decimal numbers. It evens adds the numbers in a string that contains non-numeric characters. Of course, whether that’s good or bad is not clear…

By: Lori

Lori — Mon, 05 Oct 2009 14:32:00 +0000

one more: =SUM(LEN(SUBSTITUTE(A1,{1,2,3,4,5,6,7,8,9,""},""))*-{1,2,3,4,5,6,7,8,9,-45})

don't know how it compares in speed, but is efficient in that it doesn't depend on other ranges so only recalculates when A1 changes. lhm