Vipul Gupta wrote:
> I'm interested in using Simile timeplot for plotting data values
> collected from a wireless environmental sensor (that measures light,
> temperature etc) at periodic intervals. On some occasions, sample data
> is lost (e.g. due to the unreliable nature of the wireless link) and
> I'd like to indicate this as a gap in my plot. For example, see these
> plots drawn using Gnuplot:
> 
> http://blogs.sun.com/vipul/entry/one_and_a_half_million
> 
> The same plots drawn using the Simile timeplot widget are at:
> 
> http://blogs.sun.com/vipul/resource/SolarSPOT2/similetimeplot.html

Very cool!

> While I can highlight missing samples by using the "events" feature,
> it seems more intuitive to represent missing data as gaps. Is there an
> easy way to accomplish this? I tried inserting a blank line in the
> datasource whenever a sample was missing. While this works for
> Gnuplot, it doesn't seem to work for  timeplot. I'm new to the SIMILE
> Widget set so it's possible I've overlooked an FAQ that answers this
> question.
> 
> thanks for your time,

Unfortunately, this feature is not there... but it's something several 
people have asked.

It's a tough one, though, counter-intuitively: on one hand, I always 
wanted Timeplot to just "cope" with whatever data you throw at it. This 
'whatever data' includes both gaps in sampling *and* non-uniform sampling.

Unfortunately, implementing a way to plot that can deal with both at the 
same time is not trivial... mostly because we need to establish a way to 
differentiate between gaps and non-uniform sampling periods.

The simplest way is something crude like "if the sampling period is 
greater than x, consider it a gap", where x is a variable that you can 
define when you import the data (and you can tune based on your own data 
sampling process).

A more complicated one would be to have timeplot 're-sample' the data at 
uniform intervals... but I'm afraid of the aliasing artifacts that this 
would generate.

Thoughts?

-- 
Stefano Mazzocchi                              Application Catalyst
Metaweb Technologies, Inc.                      [email protected]
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