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Re: Maxwell's density function grinds Octave


From: Henry F. Mollet
Subject: Re: Maxwell's density function grinds Octave
Date: Sun, 22 Aug 2004 11:21:23 -0700
User-agent: Microsoft-Entourage/10.1.1.2418

The first posting, which I later found in the bulk box, included the
following code:

%To remove the grid lines within the graph surface
%To make the coloring more uniform
shading interp;

This must be the reason that Gnuplot and Matlab were running out of colors.
Henry

on 8/21/04 11:45 AM, Henry F. Mollet at address@hidden wrote:

> Why is a problem of running out of colors rather than only a problem of too
> fine a grid?  I only get two colors, red outside and green inside of what
> can be seen of the saddle.
> GNU Octave, version 2.1.46 (powerpc-apple-darwin6.6)
> G N U P L O T Version 3.8i patchlevel 0
> Henry
> 
> 
> on 8/21/04 4:40 AM, Paul Thomas at address@hidden wrote:
> 
>> Reduce the mesh dimensions by a factor 20x10!
>> 
>> ie.
>> 
>>> V = 0:20:2000;
>>> t = 273.15:10:1073.15;
>> 
>> octave did OK with the original but Gnuplot crashed!  Matlab R13 does not do
>> well with the original mesh either.  Both run out of colours for the plot.
>> 
>> Paul T
>> 
>> ----- Original Message -----
>> From: "Gad Abraham" <address@hidden>
>> To: <address@hidden>
>> Sent: Saturday, August 21, 2004 10:18 AM
>> Subject: Maxwell's density function grinds Octave
>> 
>> 
>>> Hi,
>>> 
>>> I've been trying to plot Maxwell's speed distribution equation for ideal
>>> gases on Octave, using the following code (adapted from a matlab script
>>> on http://chemistryresources.tripod.com/physical/maxwell.txt):
>>> 
>>> function surf(varargin) mesh(varargin{:}); endfunction
>>> 
>>> M = 32e-3;
>>> R = 8.31451;
>>> 
>>> V = 0:1:2000;
>>> t = 273.15:1:1073.15;
>>> 
>>> [v, T] = meshgrid(V, t);
>>> 
>>> f = 4*pi*((M./(2*pi*R.*T)).^(3/2)).*(v.^2).*exp(-M.*(v.^2)./(2*R*T));
>>> 
>>> surf(v,T,f);
>>> 
>>> xlabel('v');
>>> ylabel('T');
>>> zlabel('f');
>>> 
>>> 
>>> The problem is that on my rather fast machine (AthlonXP2800, 768MB RAM),
>>> this grinds away for almost 10 minutes, and the end result is a gnuplot
>>> window with a only few tiny lines in it.
>>> 
>>> I'm using Octave2.1, gnuplot 4.0, on Debian Linux.
>>> 
>>> 
>>> Any advice?
>>> 
>>> 
>>> Thanks,
>>> Gad
>>> 
>>> -- 
>>> http://chookies.homeunix.org
>>> 
>>> 
>>> 
>>> -------------------------------------------------------------
>>> Octave is freely available under the terms of the GNU GPL.
>>> 
>>> Octave's home on the web:  http://www.octave.org
>>> How to fund new projects:  http://www.octave.org/funding.html
>>> Subscription information:  http://www.octave.org/archive.html
>>> -------------------------------------------------------------
>>> 
>> 
>> 
>> 
>> -------------------------------------------------------------
>> Octave is freely available under the terms of the GNU GPL.
>> 
>> Octave's home on the web:  http://www.octave.org
>> How to fund new projects:  http://www.octave.org/funding.html
>> Subscription information:  http://www.octave.org/archive.html
>> -------------------------------------------------------------
>> 
> 
> 
> 
> -------------------------------------------------------------
> Octave is freely available under the terms of the GNU GPL.
> 
> Octave's home on the web:  http://www.octave.org
> How to fund new projects:  http://www.octave.org/funding.html
> Subscription information:  http://www.octave.org/archive.html
> -------------------------------------------------------------
> 



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Octave is freely available under the terms of the GNU GPL.

Octave's home on the web:  http://www.octave.org
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Subscription information:  http://www.octave.org/archive.html
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