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Re: Unbearably slow plotting (v6)

  • To: mathgroup at smc.vnet.net
  • Subject: [mg79587] Re: Unbearably slow plotting (v6)
  • From: thomas <thomas.muench at gmail.com>
  • Date: Mon, 30 Jul 2007 06:44:41 -0400 (EDT)
  • References: <f8h450$6km$1@smc.vnet.net>

On Jul 29, 6:13 am, Bill Rowe <readnews... at sbcglobal.net> wrote:

> With 1E5 and 1E6 points, this results in a plot that is
> indistinguishable from a filled rectangle. That seems to be of
> very little use. So, while I might be a bit impatient waiting
> for Mathematica on my machine to plot 1E6 points, I don't see
> why I would want to do that in the first place. What I want from
> ListPlot is something to give me an idea of trends in my data.
> Given real limits on display resolution and size, plotting 1E6
> points typically will not provide a useful plot regardless of
> how fast it plots. So why do this?

It is of course true that it doesn't make any sense to plot a million
random numbers. It is easier to just plot a filled rectangle. But,
given my application, these types of plots are quite common. Imagine I
acquire data at a rate of 10 kHz, for 10 seconds (just as an example,
this is actually on the short side), that's 100,000 points. Repeat the
experiment 9 times, and plot the 9 traces together with their average,
and you have a million points to plot. More realistic, however, are
even longer traces and more repetitions.

I am aware that one could do some clever down-sampling to reduce the
number of points to plot. I've done that, and the plot looks
indistinguishable from the full plot. Given the screen resolution, one
needs to print about 1000 points per trace in order for it to look
good. If you have 100 or so traces, however, you again get into the
regime of slow plotting (100,000 points).

What I want is exactly what you mention in your post: I want to get an
idea about the trend in my data by plotting it real quickly, without
having to process the data. Once I know what's going on, I can go on
to do all the applicable data analysis steps.

What bothers me most about this is that plotting speed is so much
worse that in 5.2, especially considering the language that is used in
the documentation describing the capabilities of the new Mathematica:

Quote (from guide/NewIn60DataVisualization): "Building on
Mathematica's strengths in large-scale data handling, numerical
optimization, and geometric computation, Version 6.0 brings a new
level of automation to data visualization - with major new original
algorithms for graph layout, immediate surface reconstruction,
automated labeling, seamless handling of unstructured data,
geometrically driven interpolation, automatic date plotting - as well
as major innovations in automated aesthetics."

Note the words "large-scale" and "a new level of automation". If I
need to add a (manual) down-sampling step to plot my large scale data
in a reasonable amount of time, I would not call that "a new level of
automation".

Sorry if this has become more of a rant.
Thomas



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