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MathGroup Archive 2001

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Re: Behaviour of Plot/ListPlot & Export

  • To: mathgroup at smc.vnet.net
  • Subject: [mg31750] Re: Behaviour of Plot/ListPlot & Export
  • From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
  • Date: Sat, 1 Dec 2001 02:43:43 -0500 (EST)
  • Organization: Universitaet Leipzig
  • References: <9u4gb3$loh$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Hi,

> 
> 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)?

It is a feature, because Plot[] try to adjust the ploting steps for
functions like Sin[1/x]. This adjustment need real numbers
and this cause the error.

> 
> 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.

AFAIK this is a known bug. It will be fixed in the next version ...

> 
> 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?

version 4.1.2 ?

Regards
  Jens


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