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MathGroup Archive 2001

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Behaviour of Plot/ListPlot & Export

  • To: mathgroup at smc.vnet.net
  • Subject: [mg31722] Behaviour of Plot/ListPlot & Export
  • From: SteveC <steve at fractalus.com>
  • Date: Thu, 29 Nov 2001 00:13:41 -0500 (EST)
  • Sender: owner-wri-mathgroup at wolfram.com

Mathematica 4.1.1.0 on Linux

If I try

Plot[Sqrt[Prime[n]/Prime[n + 1]], {n, 1, 100}]

I get:

Prime::"intpp": "Positive integer argument expected in \
\!\(Prime[1.000004125`]\)."
Prime::"intpp": "Positive integer argument expected in \
\!\(Prime[1.000004125`]\)."
Prime::"intpp": "Positive integer argument expected in \
Prime[2.0000041250000002`]."

And a bunch more errors, however if I try

ListPlot[Table[Sqrt[Prime[n]/Prime[n + 1]], {n, 1, 100}]]

Then it works fine. Presumably Table[x,{x,1,100}] steps through integers 
while Plot does not. This is surprising, I expected the same behaviour of 
them. Is this a bug? Is this documented (I did look around)?

I have been doing a lot of work with Export[]ing single cells and animated
Gifs. I find Mathematica on something like
Export["somefile.gif",Table[<big list of graphics>]] will produce the
graphics and then export individual frames to /tmp/m<some number> as PNM 
files *incredibly* slowly. It will take 3 minutes per image and they are 
not complex images.

The CPU is not utilised during that time, only in small bursts, wait a few 
minutes then do the next. For 100 cell animations this is frustrating. The 
process tree has PNM.exe and GIF.exe running but doing nothing. Perhaps 
they are timing out on some operation? I could run traces for the truely 
interested...

Once it has exported all the images it appears to then keep them all in
memory before creating the GIF. I recently had a 600 frame animation [I
appreciate this should be in an mpeg, and I did so] where mathematica used
1 Gigabyte of memory plus 128 meg of swap before the kernel VM killed it
for eating all available resources. I respectfully suggest this
architecture is flawed. I am now using ImageMagick for all of these
operations. :-/

Also, Mathematica has a bug that I submitted where it crashes on changing 
some prefs which was confirmed.

As an aside is there a version release > than mine and if so am I able to 
obtain it?

tia

SteveC steve at fractalus.com fractalus.com/steve


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