Re: determinent of undefined matrix?

[Geraint Paul Bevan]

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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 octave-forge. 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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