Re: lsode twice problem

[Robert Durkacz]

On 18 January 2014 13:40, Montgomery-Smith, Stephen
<address@hidden> wrote:
    On 01/17/2014 02:17 PM, marciopfrs wrote:
    > I'm using the following commands to solve the ODE:
    ...
    > I tried a lot but was not able to use the solution "y" of this ODE in
    > another ODE
    > How can I do this?

    The easiest thing is to solve for y and w simultaneously:
    ...

I am interested in the question raised by marciopfrs, and the answer
given by Stephen Montgomery-Smith. The answer is to use the lsode call
more intensively rather than use Octave and I think this is because
Octave cannot offer any help in this case.

M-S's answer may be entirely satisfactory in the context that the
question was asked, but it is not intended to answer for the general
situation. In the general situation we would like to define a function
using differential equations and then use that function whenever.
Octave gives you no support for that as far as I can tell. I think you
have to come up with your own solution of generating a large enough
tabulation from the solutions of the differential equations and then
define the function, which is implemented to look up the tables,
interpolating as necessary.

My answer is based on the limited knowledge of what I found I had to
do in a similar situation.

Another thing by the way is that the choice of variable names in the
question makes it hard to understand what lsode is doing and which are
the dependent and independent variables. Better is how the manual
expresses it, in terms of xdot, x and t (no y).