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## System of ODE's - Part II

 From: Dennis Bayrock Subject: System of ODE's - Part II Date: Fri, 28 Sep 2001 10:50:37 -0600 User-agent: Mozilla/5.0 (Windows; U; WinNT4.0; en-US; rv:0.9.4) Gecko/20010913

```Hello All!

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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.
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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.
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The hypothetical equations are:

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

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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.
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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.
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Dennis Bayrock, P.hD.

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