[R-sig-dyn-mod] Damped oscillator with deSolve

[Felix Schönbrodt]

Perfect - thanks a lot to both of you!
Felix


Am 07.12.2012 um 08:38 schrieb Thomas Petzoldt <Thomas.Petzoldt at TU-Dresden.de>:

> On 12/6/2012 8:02 PM, Suzen, Mehmet wrote:
>> Hello Felix,
>> 
>> You need to introduce new variable y=dx/dt  and your equation reads
>> dy/dt= eta*x + zeta*y.  So solution
>> will be for states (x, y) and paramaters (eta, zeta). Remember that
>> any higher order ODE can be expressed as first order.
> 
> Yes, right, cf. page 3+4 in:
> 
> http://journal.r-project.org/archive/2010-2/RJournal_2010-2_Soetaert~et~al.pdf
> 
> 
> so you may get something like:
> 
> library(deSolve)
> 
> osci <- function (t, states, parms) {
>  with(as.list(c(states,  parms)), {
>    dx <- y
>    dy <- -eta * x - zeta * y
>    list(c(dx, dy))
>  })
> }
> 
> states <- c(x = 1, y = 0)
> out <- ode(states, osci, times = 0:100,
>  parms = c(eta = 0.2, zeta = 0.1))
> plot(out)
> 
> 
> 
> Have fun!
> 
> Thomas P.
>