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## can i do ODE2 problems with lsode ?

 From: John Utz Subject: can i do ODE2 problems with lsode ? Date: Thu, 30 Nov 1995 11:56:19 -0800 (PST)

```Hi gang;

I have been trying to do some neural-net and dynamical systems
stuff that i have been assigned as homework.

This means i need to solve ODE's and sytems of ODE's. Octave has
dassl and lsode for this purpose. I am not sure how i need to pre process
my equations to get them into a form that lsode or dassl would be willing
to digest.

The example in the manual for lsode is pretty good, the entry for
dassl does not have an example, but the description seems pretty complete.

Here is the function that i want to try and solve first, since i
think it is a "simple" example of what comes in the real stuff.

d^2 x                       dx
----- + lambda*( x^2 - 1 )* -- + x = 0
dt^2                        dt

so we can plunk 3 in for lambda, this is supposedly an equation from a
matlab demo, but i dont have matlab, so i dont know.

my problem is that this is a 2nd order eq and lsode looks like it only
wants 1rst order eq's.

Now, i *thought* that any nOrder ode can be represented as an
Nsystem of 1rst order diffeq's. I starting to think that i hallucinated
this fact because i cant seem to find any example of this in either
Boyce/DiPrima or Jordan/Smith, which are the two textbooks on the subject
of ode's that i have at my disposal.

So, did i hallucinate this? If not, can anybody provide any
suggestions as to how i might implement this?

tks folks, please feel free to tell me if u think this was an
inapropriate use of the list.

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