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Re: Unbearably slow plotting (v6)David Bailey,

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  • Subject: [mg79649] Re: Unbearably slow plotting (v6)David Bailey,
  • From: Bill Rowe <readnewsciv at>
  • Date: Wed, 1 Aug 2007 04:58:33 -0400 (EDT)

On 7/30/07 at 6:39 AM, dave at (David Bailey)

>Bill Rowe 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

>The main reason people do this, is that they have experimental data
>which they want to visualise without having to filter it in some way
>to remove redundant data points.

I certainly understand the need to visualize experimental data
since that is one of the things I do most frequently with
Mathematica. And I also understand the desire to do this as
easily and efficiently as possible.

But Mathematica is not a substitute for thinking about your
data. If you ask Mathematica to plot a million points it will do
so in whatever time is required. But such plots are almost never
a good way to visualize data given typical sized displays and
their resolution.

In fact, one of the nice things about version 6 is it makes
simple filtering such as taking every nth point very easy. For
example, if I had 1E6 data points, I likely would initially plot
every 100th point or every 1000th point to get a reasonable
plot. As I am sure you are aware doing:

ListPlot[datra[[;; ;;100]]]

in version 6 will plot every 100th point.

Yes, there is always a risk in using such simple filtering
schemes important aspects of the data will be missed. But that
same risk exists if all data points in such a large set are
plotted. If there are only a few important points, plotting all
of the points will almost certainly obscure the few important points.
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