# [Maxima] plot2d failed to plot too many discrete points

Richard Fateman fateman at eecs.berkeley.edu
Sun May 13 19:11:21 CDT 2012

```Another idea

On 5/13/2012 2:09 PM, Richard Fateman wrote:
> On 5/13/2012 7:43 AM, XeCycle wrote:
>> Richard Fateman<fateman at eecs.berkeley.edu>  writes:
>>
>> [...]
>>
>>> I have  fairly nice computer display, and it has about 1.6
>>> million discrete pixels.
>>> Plotting 2 million discrete non-overlapping points on it would
>>> not be possible.
>>> Perhaps you would find difficulties regardless of the plotting program.
>>> RJF
>> You're missing the point.  This many numbers are needed for my
>> computation, and will be further processed; now I want to have an
>> impression on how it looks like, so I tried to plot it.

If you want to know what it looks like, how about plotting only every
1000th point.
That still gives you several thousand points plotted, and that may give
you an impression.
Or you could take points that are some random number between 1 and 2000
apart.
Do it several times.
If the plot looks the same each time, you have some info to go on.

It cannot be that each of the millions of points has something to
contribute, for the
reason I gave previously.

I have frequently found that persons approach solving a problem by computer
with insufficient consideration for the limitations of computing,
requiring huge
amounts of work for negligible payoff, or involving long sequences of
arithmetic
without considering that the result may have lost all significant digits
to essentially
random bits of round-off.

Sometimes this doesn't matter because the computation is supposed to mirror
some physical phenomenon which cannot ever be exhibited in reality and whose
further exploration by computer simulation is essentially irrelevant
except as an
academic exercise.  Computer algebra systems can sometimes be used for
such pointless exercises where usual numerical computation can't be used.
You haven't told us anything much about your exercise and whether there
is some reason you are using Maxima instead of (say) Matlab.

The fact that something is not in a system (or is not documented...) or
"doesn't seem to work" is occasionally a useful hint that maybe it is
not a sensible thing to do.

RJF

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