From help-octave-request at bevo dot che dot wisc dot edu Sun Nov 23 20:29:54 2003
Subject: Re: Passing parameters to ODEs
From: Geordie McBain <geordie dot mcbain at aeromech dot usyd dot edu dot au>
To: eiffleduarte at petrobras dot com dot br
CC: help-octave at bevo dot che dot wisc dot edu
Date: Mon, 24 Nov 2003 13:25:50 +1100

> I am new to Octave and been trying to run my Matlab code under it.
> Can I pass parameters to ODEs without using globals? I tried this
> with ode45, but it didn't work. I looked the help for lsode and it
> also does not give me such an option. Is there a way to do it?
> Also, are there any optimization routines that allow me to pass
> parameters to the objective functions without using globals?

> Sincerely,

> Marcus Vinicius Eiffle Duarte

Here are two ways to pass parameters to ODEs.

1) Say the ODE depends on a parameter p.  Append p as a dependent
   variable and give it the evolution equation dp/dt=0 and the
   appropriate initial condition.

2) Try Octave's odessa function instead of lsode.  Call is 

       [X, SX, ISTATE, MSG] odessa (FCN, X_0, P, SX_0, T, T_CRIT)

   where P is a vector of parameters; see under `Differential
   Equations/Ordinary Differential Equations' in the manual for more
   information.



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