[R-sig-dyn-mod] Modify times parameter in lsoda at runtime

[Faelens Ruben]

Hello,

I have a dynamic model where I do not know my observation times
beforehand. I only have a single event declared at t=10, and this event
determines the next observation time for the model.

I currently have implemented this as follows:

IV <- c(15, 20, 30)
t <- 0
next_t <- 15
while( ! is.na(next_t) ) {
    out <- lsoda(
      y=IV,
      model=MyModel,
      times=c(t, next_t),
      parms=NA
    )
    IV <- out[2, 2:5]
    t <- next_t
    next_t <- if( IV[1] < 10 ) { t + 1 * IV[1] } else { t + 30 * IV[1] }
}

Unfortunately, this is very slow, because LSODA needs to initialize the
stepsize each time.
I can fire an event using the 'events' functionality of LSODA, but I
cannot modify the times parameter or the events array once the ODE
integration is running. Preferably, I would do something like this:

FireEvent <- function(t, y, parms) {
    events$func <<- FireEvent
    events$time <<- if( IV[1] < 10 ) {
	t + 1 * IV[1]
    } else {
      t + 30 * IV[1]
    }
}
IV <- c(15, 20, 30)
events <- as.data.frame(list(func=FireEvent, time=10))
out <- lsoda(
  y=IV,
  model=MyModel,
  times=c(0, Inf),
  parms=NA,
  events=events
)    

Is it at all possible to modify the 'times' or 'events' parameter for
LSODA while it is running?

/ Ruben Faelens