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Re: determinent of undefined matrix?
From: 
Geraint Paul Bevan 
Subject: 
Re: determinent of undefined matrix? 
Date: 
Sat, 11 Sep 2004 00:59:05 +0100 
Useragent: 
Mozilla Thunderbird 0.5 (X11/20040306) 
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NZG wrote:
 I want to solve the determinent of a matrix containing an unknown s
such as

 det[s 1;1 s]

 ans
 s^2  1

 in Matlab I just define
 s = sym('s')
 beforehand.

 This doesn't work in Octave, what's an equivalent method?
 Does one exist?

The sym function is part of octaveforge. I don't use it often (I
usually use symbolic algebra tools for symbolic work) but using a recent
version (2004.07.07, on Debian), it does seem to be broken.
octave> s = sym('s');
octave> [s,0]
error: octave_base_value::array_value(): wrong type argument `ex'
I don't know what the cause of this is, but if you must do symbolic work
in Octave, you could try using gino:
http://sourceforge.net/projects/mtt
octave> g_determinant ("[[s,1],[1,s]]")
ans = 1+s^2
If you have a lot of symbolic work to do, there is a list of several
computer algebra systems which you might find useful on the Octave wiki:
http://wiki.octave.org/wiki.pl?CategorySymbolic
 
Geraint Bevan
http://homepage.ntlworld.com/geraint.bevan
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