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Topic: Plotting data with microsecond accuracy
Replies: 3   Last Post: Apr 17, 2013 10:05 AM

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 dpb Posts: 9,850 Registered: 6/7/07
Re: Plotting data with microsecond accuracy
Posted: Apr 16, 2013 1:46 PM
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On 4/16/2013 12:08 PM, Kevin wrote:
> I am trying to plot voltage values that have been sampled at 50 us
> intervals. Each of these samples have been timestamped so that they can
> be compared with other measurements. I've converted the timestamps to
> datenum values but when I use the PLOT function, the x-axis is scaled in
> such a way that all of my data is compressed to the centre of the plot.
> I have tried manipulating the axis using xlim and datetick but nothing
> changes. What I really need to be able to is zoom in on specific areas
> of the plot while safegaurding the timestamps and scaling the axis
> accordingly. Any advice would be much appreciated.
>

If you're coding in the absolute clock time to the us the problem is
that the resolution of DATENUM is being stretched to its limits. I just
tried here and the best I can get w/ xlim on the x-axis w/ a current
year datenum magnitude is roughly 10E-4 sec whereas the resolution of 1
ms on a datenum is otoo 10E0-8. Thus, while I could get a wider
vertical line than the default single pixel, it is still essentially a
vertical line.

If you need to also know the real time associated w/ that record I think
you'll have to keep that separate of the actual time record--I'd
probably just count the time series itself in us from wherever sample
starts in the record and then if need to date it write that as a text
string.

--

Date Subject Author
4/16/13 Kevin
4/16/13 dpb
4/17/13 Kevin
4/17/13 dpb

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