System of ODE's - Part II

[Dennis Bayrock]

Hello All!

   First off, I would like to thank everyone for their quick reply to 
my posting - it is nice to see such a fast turnaround to a help question!
   Although everyone's input helped me and I have re-read the manual, I 
am still having problems understanding Octave's syntax in integrating 
ODE's. I am not an engineer or a mathematician but rather a fermentation 
microbiologist. Despite this shortcoming ( :)  ) I can construct ODE's 
and see the value in integrating them.

   OK now on to my ongoing question. I see that my posting last time 
did not quite emphasize what I was trying to get help on (my fault) so I 
will try again. I will not use my model in this example but rather a 
hypothetical example so that: 1. People don't feel I am trying to elicit 
an answer from them (i.e. you doing my work), 2. I hope that someone 
will give me an explicit answer on how to actually enter the equations 
into Octave, and 3. My models are confidential.

The hypothetical equations are:

dX/dt = X * S * dP/dt
dS/dt = X * P * dX/dt
dP/dt = X + dS/dt + dX/dt


Ignore initial conditions for now. Notice first that X,S, and P on the 
right side of the equations are not constants. Also some of the 
differential equations are part of (nested within) other differential 
equations. Could someone please show me how they would actually enter 
these differential equations into Octave so that it can integrate them? 
I can then apply the correct syntax from this example to my actual model.

On a side note. Is there a way to symbolically enter these equations 
into Octave? If not then I would strongly suggest this to be explored 
and put into the next version of Octave so that people like me can more 
easily use it.

   Thank's all in advance!

       Dennis Bayrock, P.hD.




-------------------------------------------------------------
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
-------------------------------------------------------------