plotting epoch time with nanoseconds

Hello:

I got two sets of data, both are epoch time with nano seconds, shown as below:

when I try to plot them, I got two exact same lines, as shown below:

How can I plot the difference in these two lines, i.e. bring up the precision including nano seconds, please?

Thank you in advance for any help.

Regards.

Answer 1

[Rik]

There are several ways you could plot this. Possibly the easiest is to simply plot the difference:

plot(T2-T1)

Other possibilities are to plot against the difference to the mean (like a Bland-Altman plot), or to fit a linear function to this data (with polyfit e.g.) and plot the time difference with that function.

[parhat remtulla]

Hi:

Thank you very much for your answer, it is easy to see the difference.

It is supposed to be something like:

[Rik]

Clearly the differences are not large enough to be seen in the plot you suggest. Why not try that plot(T2-T1) I suggested. You should also keep in mind the comment made by Peter Perkins.

If my answer helped you, please mark it as accepted answer. It will make it easier for other people with a similar question. If Peter Perkins's answer is more helpful, please mark that one.

Answer 2

[Peter Perkins]

You say, "with nanoseconds", but in fact what you show is not out to nanosecond precision, only to microsecond. Which is good, because double precision doesn't have enough bits to represent nanoseconds since 1970, and only just barely enough to represend microseconds since 1970.

>> t = 1500469584.003352 % 19-Jul-2017 13:06:24.003352, approximately
t =
     1.500469584003352e+09
>> eps(t)
ans =
     2.384185791015625e-07

So if you do have timestamps that go out to nanoseconds, and your differences are on the order of nanoseconds, you'll be plotting noise, not data.