[R-sig-dyn-mod] replicates in stochastic model

Hi all,

I am trying to model a simple demographic stochastic system in R, and its
trajectorie during some years. For doing that I have written the following
code:

times=c(1:100)
Nt=rpois(times, 10)
phi=runif(times, 0.1,1)
ri=rpois(times, 10)
Ii=rpois(times,5)

popmod<-function(times, Nt, phi, ri, Ii){
for (i in times[-1]){
Nt[times-1]*phi[times-1]+ ri[times-1]+Ii[times-1]
				}
F=data.frame(Nt=Nt[times],year=times)

}


vf<-popmod(times, Nt, phi, ri, Ii)

Now, what I want is to run some replictes (about 100) of the same model to
obtain the estimate and standard deviation of the trajectorie. I have
tried with the repeat loop, but until now all my attemps have failed.

Can anyone plese provide me some guidance and/or help?

Thanks in advance, best regards

Pablo