[time-nuts] Excel logarithmic function (was Thermal impact on OCXO)

Lars Walenius lars.walenius at hotmail.com
Fri Nov 18 13:26:44 EST 2016

Bob wrote:
>As mentioned earlier in this thread. The function that has been used in several posts
>isn’t the right log function. The proper fit is to ln(bt+1)

You are absolutely right. It was my mistake to use the ln(t) in the graph. As that was what I know in Excel and I don´t have Stable32 or MatLab. In Excel I actually double checked that (a*ln(bt+1)) with b 5 to 1000 gave about the same as (a*ln(t)) for my data set (only the offset was largely different).

Hopefully someone can find the correct a and b for a*ln(bt+1) with stable32 or matlab for this data set:
Days ppb
2       2
4       3.5
7       4.65
8       5.05
9       5.22
12     6.11
13     6.19
25     7.26
32     7.92

It would also be interesting if I could get the drift after 10 years to see if it is about 6E-13/day as with the ln(t).

Peter wrote:
>> I'm not very good with Excel, but this curve-fitting function sounds very
>> useful.  Could you please tell me how it's done?

In the graph I only right-clicked the curve and selected ”add trendline” here I checked the logarithmic and show equation.


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