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Re: octave and delay ode's
From: |
Carlo de Falco |
Subject: |
Re: octave and delay ode's |
Date: |
Mon, 2 Nov 2009 00:00:54 +0100 |
On 1 Nov 2009, at 20:08, franco basaglia wrote:
I must be missing something as in your file I see no time
derivatives...
sorry for my oversight. I attach again pdf with right system.
What exactly does "delta t" mean in your file?
function f = fun (t, y, yd)
f(1) =-y(1) + yd(2);
f(2) =-y(2) ;
endfunction
ode23d (@fun, [0 5], [1;1], .1, [1;1])
notice that in the example above only one equation includes a delay:
is this what you mean by system of ODEs and DDEs?
Yes,sure.
To be more precise I have a system like this:
d y1(t)/ dt = -y1(t)
d y2(t)/ dt = -y2(t) + y1(t-5)
d y3(t)/dt = -y3(t) + y2(t-10)*y1(t-10)
that I try to solve in this way:
function f = fun (t, y, yd)
f(1) =-y(1)
f(2) =-y(2) + yd(1)
f(3) =-y(3) + yd(2)*yd(1)
endfunction
t = [0:.5:20]
res = ode45d (@fun, t, [1;1;1], [5;10], ones (3,10))
I think this should rather be something like:
function f = fun (t, y, yd)
f(1) =-y(1); %% y1' = -y1(t)
f(2) =-y(2) + yd(1,1); %% y2' = -y2(t) + y1(t-lags(1))
f(3) =-y(3) + yd(2,2)*yd(1,2); %% y3' = -y3(t) + y2(t-lags(2))*y1(t-
lags(2))
endfunction
T = [0,20] %% only initlial
and final time
%% need to be
provided
res = ode45d (@fun, t, [1;1;1], [5, 10], ones (3,2)); %% number of
columns in HIST should
%% be the same
as the number of columns
%% in LAGS
I beleive Thomas Treichl, the author of odepkg is listening on the
list so maybe he can confirm whether this is correct?
It's run. But I don't think this is the right way.I don't know if
with this notation it applies a delay of 5 time units to f(2) and of
10 time units to f(3).
what do you mean by "time units"?
Note that in f(3) yd(1) comes again but with a different delay.
Infact for my script, that I attach here, is the same. It's runs but
with different results compare to Stella.
Any Idea?
From your pdf file and your script I get the feeling that you are
confusing the
time parameter in the continuos problem and the number of time-steps
in the discretized
system...
thanks a lot
f.t.
c.
P.S. please keep the list in CC as someone else may want to help with
your questions
or benefit from the answers.
equazioniPatu.pdf
Description: Adobe PDF document
scriptode45.m
Description: Text Data
- octave and delay ode's, franco basaglia, 2009/11/01
- Re: octave and delay ode's,
Carlo de Falco <=
- Re: octave and delay ode's, Thomas Treichl, 2009/11/02
- Re: octave and delay ode's, Carlo de Falco, 2009/11/05
- Re: octave and delay ode's, Thomas Treichl, 2009/11/05
- Re: octave and delay ode's, Carlo de Falco, 2009/11/05
- Re: octave and delay ode's, franco basaglia, 2009/11/07
- Re: octave and delay ode's, Carlo de Falco, 2009/11/07
- Re: octave and delay ode's, Carlo de Falco, 2009/11/07
- Re: octave and delay ode's, franco basaglia, 2009/11/13
Re: octave and delay ode's, franco basaglia, 2009/11/03