From: Stephen Leake <stephen_leake@stephe-leake.org>
Subject: Re: how to analyze clock drift
Date: Thu, 20 Nov 2014 10:27:34 -0600
Date: 2014-11-20T10:27:34-06:00 [thread overview]
Message-ID: <85a93lon0p.fsf@stephe-leake.org> (raw)
In-Reply-To: 87fvdeet0q.fsf@debian.uxu
Emanuel Berg <embe8573@student.uu.se> writes:
> Jacob Sparre Andersen <jacob@jacob-sparre.dk> writes:
>
>> Try to subtract a linear fit and plot the result.
>> There may be a short-term systematic pattern, but
>> over longer time, it looks like you have a slowly,
>> randomly drifting function.
>
> You mean, I should make a figure (graph) and then
> learn from it by inspecting it?
>
> By "subtract a linear fit", do you mean I should
> broadly visualize this as a linear function by some
> smoothing-out filter even though the data of course
> isn't a straight line?
Just use a standard "linear fit" algorithm
(http://en.wikipedia.org/wiki/Linear_regression,
http://stephe-leake.org/ada/sal.html sal-math_double-linear_fit.ads) to
fit the data to y_fit = mx + b, then plot y - y_fit.
That will show the short term sawtooth, plus any longer term drift.
The short term sawtooth is probably due to the way the software is using
a hardware clock; the clock period doesn't quite divide the desired
software period.
--
-- Stephe
next prev parent reply other threads:[~2014-11-20 16:27 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-11-18 22:12 how to analyze clock drift Emanuel Berg
2014-11-19 1:41 ` tmoran
2014-11-19 2:10 ` Emanuel Berg
2014-11-19 10:30 ` Jacob Sparre Andersen
2014-11-19 22:15 ` Emanuel Berg
2014-11-20 16:27 ` Stephen Leake [this message]
2014-11-20 1:10 ` Emanuel Berg
2014-11-20 14:11 ` Dennis Lee Bieber
2014-11-19 13:08 ` Brian Drummond
2014-11-19 2:10 ` Simon Clubley
2014-11-19 2:37 ` Emanuel Berg
2014-11-19 2:28 ` Dennis Lee Bieber
2014-11-19 2:44 ` tmoran
2014-11-19 2:51 ` Emanuel Berg
2014-11-19 9:01 ` Dmitry A. Kazakov
2014-11-19 22:12 ` Emanuel Berg
2014-11-20 9:42 ` Dmitry A. Kazakov
2014-11-20 20:41 ` Emanuel Berg
2014-11-20 21:27 ` Dmitry A. Kazakov
2014-11-20 21:54 ` Emanuel Berg
2014-11-20 21:57 ` Emanuel Berg
2014-11-21 2:27 ` Dennis Lee Bieber
2014-11-21 3:02 ` Emanuel Berg
2014-11-21 16:49 ` Dennis Lee Bieber
2014-11-21 21:06 ` Emanuel Berg
2014-11-22 18:18 ` Dennis Lee Bieber
2014-11-23 20:15 ` Emanuel Berg
2014-11-24 1:15 ` Dennis Lee Bieber
2014-11-24 1:34 ` Emanuel Berg
2014-11-24 9:22 ` Jacob Sparre Andersen
2014-11-24 17:30 ` Dennis Lee Bieber
2014-11-24 8:44 ` Dmitry A. Kazakov
2014-11-24 17:24 ` Dennis Lee Bieber
2014-11-24 18:28 ` Dmitry A. Kazakov
2014-11-24 20:30 ` brbarkstrom
2014-11-24 21:03 ` Dmitry A. Kazakov
2014-11-24 21:34 ` brbarkstrom
2014-11-25 14:04 ` brbarkstrom
2014-11-25 18:16 ` Dennis Lee Bieber
2014-11-25 20:50 ` brbarkstrom
2014-11-21 21:15 ` Emanuel Berg
2014-11-21 22:31 ` Emanuel Berg
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