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> Log Function
kvarnerexpress
post Sep 5 2005, 08:49 AM
Post #1


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Member No.: 2,696
Hi all.

I have some prob with log function.
The code below is not working, it returns a false value.
The value is not same with what I calculate using scientific calculator.

Using my program:
N=2
Na=1
log(N/Na)=0.6931

Using scientific calculator:
N=2
Na=1
log(N/Na)=0.30102999566

Code:

CODE
Na = 0
temp = 0
temp1 = 0
rs.MoveFirst
Do
   For column = 1 To rs.Fields.Count - 1
       'If rs.Fields(column) <> Null Then
       If Not IsNull(rs.Fields(column).Value) Then
           Na = Na + 1
       End If
   Next column
   N = rs.Fields.Count - 1
   temp = Log(N / Na)
   temp1 = Format(temp, "0.0000")
   rs2.AddNew
   rs2!Na = temp1
   rs2.Update
Na = 0
rs.MoveNext
Loop Until rs.EOF



kvarnerexpress

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Galahad
post Sep 6 2005, 07:25 AM
Post #2


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From: Novi Sad, Vojvodina
Member No.: 2,127
Yes, I had that same problem once...
In Visual Basic, LOG function is returning a value of natural logarithm (base2), whereas in math LOG specifies Base10 logarithm (or at least I think so). Now, in scientific calculator, you might have noticed LN button, just above the LOG button. If you do that function, you will get the value you want. So, in order to get the numbers you need, use this code or put it in a function:
CODE

Public Function MyLog(ByVal Number As Double) As Double
 MyLog = Log(Number) / Log(10)
End Function


This should give you the values you need, so your code might look something like this:
CODE

Na = 0
temp = 0
temp1 = 0
rs.MoveFirst
Do
  For column = 1 To rs.Fields.Count - 1
      'If rs.Fields(column) <> Null Then
      If Not IsNull(rs.Fields(column).Value) Then
          Na = Na + 1
      End If
  Next column
  N = rs.Fields.Count - 1
  temp = Log(N / Na) / Log(10)
  temp1 = Format(temp, "0.0000")
  rs2.AddNew
  rs2!Na = temp1
  rs2.Update
Na = 0
rs.MoveNext
Loop Until rs.EOF

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dul
post Oct 20 2005, 02:34 AM
Post #3


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Posts: 73
Joined: 21-September 05
Member No.: 12,113
Hi. It is must be a same result. Because mathemathics didn't change. Check your code.

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