pls help newbie with my significant figures function

[James Bond]

Hello. I am having a little trouble with a simple little function I wrote
to handle significant figures in excel. I just created a VBA module with
this simeple code;

Function Sig(BaseNum, NumSigDig)

Sig = Round(BaseNum, NumSigDig - Len(Int(BaseNum)))

End Function

The intended functionality of this would be something like if R1C1=
42.0037 then =sig(a1,5) would return the number 42.004 (rounded to 5
significant digits).

Now this function mostly seems to work like a charm (there are some
limitations in this implementation but they are expected and not the
subject of this post)

What really has me stumped is the function seems to only work where
BaseNum (the number to rounded) is less than 10000 (so 9999.9999999 works
okay, but not 10000).

I am very new to VBA so I don't understand how data types are being
handled well enough to troubleshoot this problem. Any advice would be
greatly appreciated.

Thanks

James

 

[James Bond]

Hello. I am having a little trouble with a simple little function I
wrote to handle significant figures in excel. I just created a VBA
module with this simeple code;

Function Sig(BaseNum, NumSigDig)

Sig = Round(BaseNum, NumSigDig - Len(Int(BaseNum)))

End Function

The intended functionality of this would be something like if R1C1=
42.0037 then =sig(a1,5) would return the number 42.004 (rounded to 5
significant digits).

Now this function mostly seems to work like a charm (there are some
limitations in this implementation but they are expected and not the
subject of this post)

What really has me stumped is the function seems to only work where
BaseNum (the number to rounded) is less than 10000 (so 9999.9999999
works okay, but not 10000).

I am very new to VBA so I don't understand how data types are being
handled well enough to troubleshoot this problem. Any advice would be
greatly appreciated.

Thanks

James

Oh, I probably should have mentioned that when I say my function doesn't
work for values of 10000 or greater I mean that I get a #VALUE error in
the the spreadsheet.

Thanks again.
James

 

[Vasant Nanavati]

Have you tried this solution from Dana DeLouis?

Function SigDigits(n, d As Integer)
' = = = = = = = = = = = = = = = = = = = =
' Rounds a number(n) to (d) significant figures
' By: Dana DeLouis, (e-mail address removed)
' = = = = = = = = = = = = = = = = = = = =
SigDigits = Val(Format(n, String(d, "#") & "E+00"))
End Function

 

[Ron Rosenfeld]

Hello. I am having a little trouble with a simple little function I wrote
to handle significant figures in excel. I just created a VBA module with
this simeple code;

Function Sig(BaseNum, NumSigDig)

Sig = Round(BaseNum, NumSigDig - Len(Int(BaseNum)))

End Function

The intended functionality of this would be something like if R1C1=
42.0037 then =sig(a1,5) would return the number 42.004 (rounded to 5
significant digits).

Now this function mostly seems to work like a charm (there are some
limitations in this implementation but they are expected and not the
subject of this post)

What really has me stumped is the function seems to only work where
BaseNum (the number to rounded) is less than 10000 (so 9999.9999999 works
okay, but not 10000).

I am very new to VBA so I don't understand how data types are being
handled well enough to troubleshoot this problem. Any advice would be
greatly appreciated.

Thanks

James

Here are some routines to round to significant digits:


VBA
==============================
Function RoundSigDigits(N As Double, SigDigits As Integer) As Double
RoundSigDigits = Application.WorksheetFunction.Round _
(N, Fix(-Log(Abs(N)) / Log(10)) + SigDigits + (Abs(N) > 1))
End Function
========================

Various worksheet formulas:

=ROUND(F1,TRUNC(-LOG(ABS(F1)))+SigDigits-(ABS(F1)>1))

=ROUND(A1,SigDigits-1-INT(LOG10(ABS(A1)))) (Walkenbach)

=--TEXT(A1,"."&REPT("0",SigDigits)&"E+000") (Harlan)

============================
--ron

 

[Ron Rosenfeld]

Hello. I am having a little trouble with a simple little function I wrote
to handle significant figures in excel. I just created a VBA module with
this simeple code;

Function Sig(BaseNum, NumSigDig)

Sig = Round(BaseNum, NumSigDig - Len(Int(BaseNum)))

End Function

The intended functionality of this would be something like if R1C1=
42.0037 then =sig(a1,5) would return the number 42.004 (rounded to 5
significant digits).

Now this function mostly seems to work like a charm (there are some
limitations in this implementation but they are expected and not the
subject of this post)

What really has me stumped is the function seems to only work where
BaseNum (the number to rounded) is less than 10000 (so 9999.9999999 works
okay, but not 10000).

I am very new to VBA so I don't understand how data types are being
handled well enough to troubleshoot this problem. Any advice would be
greatly appreciated.

Thanks

James

I forgot to answer your question about why your routine didn't work.

In recent versions of VBA, the VBA Round function is different from the Excel
worksheet function. In the VBA Round function, I do not believe that
numdecimalplaces can be negative.

If you prefer your routine to the one's I provided, you could either restrict
numdecimalplaces to being not less than zero, or use worksheetfunction.round


--ron

 

[James Bond]

I forgot to answer your question about why your routine didn't work.

In recent versions of VBA, the VBA Round function is different from
the Excel worksheet function. In the VBA Round function, I do not
believe that numdecimalplaces can be negative.

If you prefer your routine to the one's I provided, you could either
restrict numdecimalplaces to being not less than zero, or use
worksheetfunction.round


--ron

Ahhh, that would certainly explain the problems I was having. Thank you
very much for that explanation as well as the info on other ways to
achive my goals.

James