Craig O'Connell-2 wrote:
>
> Dear R-users,
>
> I am currently modifying a previously developed predator prey model and
> was curious if there was a way to add in a disturbance to the model (let's
> say at time t=100). The disturbance can be the introduction of 40 prey
> (N=40) and 10 predators (Pred = 10). I would like to see my model go from
> a
> state of equilibrium (up to t = 99), show this disturbance (at t = 100)
> and
> then slowly work its way back to equilibrium. Does anybody know if this
> could be done?
>
You can also use package simecol, (imports deSolve), as follows:
library(simecol)
LVmod0D <- new("odeModel",
main = function(time, state, pars) {
with(as.list(c(state,pars)), {
IngestPred <- rI * N * Pred
GrowthN <- rG * N * (1 - N/K)
MortPred <- rM * Pred
dN <- GrowthN - IngestPred
dPred <- IngestPred * AE - MortPred
return(list(c(dN, dPred)))
})
},
parms = c(rI = 0.1, rG = 0.9, rM = 0.8, AE = 0.9, K = 20),
times = seq(0, 200, by = 1),
init = c(N = 20, Pred = 20) ,
solver="lsoda"
)
# from reply of previous poster
Levents <- list(data=data.frame(var=c("N","Pred"),time=rep(100,2),
value=c(40,10),method=rep("add",2)))
Levents
lv.sim <- sim(LVmod0D,events=Levents)
lv.out <- out(lv.sim)
lv.out
plot(lv.sim)
I'm not quite sure if the specification of the events is what you need. If I
understood correctly this would be more what you want:
Levents <- list(data=data.frame(var=c("N","Pred"),time=rep(100,2),
value=c(40,10),method=rep("rep",2)))
best
Berend
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