In EcoForecast/ecoforecastR: Ecological forcasting tools

#par(mfrow=c(2,1))
nt = 80
time = 1:nt
Y.err = Tot.err = matrix(1,2,nt)
r = c(0.95,1.01)
e = 0.2
for(t in 2:nt){
  Y.err[,t] = r*Y.err[,t-1]
  Tot.err[,t] = r*Tot.err[,t-1] + e
}
plot(time,Y.err[1,],ylim=c(0,max(Y.err)),type='l',
     ylab="Predictive Error",main="Initial Conditions",lwd=3,
     cex.lab=1.25)
lines(time,Y.err[2,],lwd=3)
text(time[40],Y.err[,40]+max(Y.err)*0.1,c("df/dY < 1","df/dY > 1"))

nv = 3  ## natural variability
plot(time,Tot.err[1,],ylim=c(0,2*max(Tot.err[1,])),type='l',
          ylab="Predictive Error",main="Total Error",lwd=3,
          cex.lab=1.25)
lines(time,Tot.err[2,],lwd=3)
abline(h=nv,lty=2)
int = apply(Tot.err,1,function(x){findInterval(nv,x)})
arrows(time[int],nv,time[int],0,length=0.1)
text(time[40],c(Tot.err[1,40]+2*max(Tot.err[1,])*0.13,2*max(Tot.err[1,])*0.95),c("df/dY < 0","df/dY > 0"))
text(time[nt*0.9],0.75*nv,"Natural\nVariability")