library(fpp)
beer2 <- window(ausbeer,start=1992,end=2006-.1)
beerfit1 <- meanf(beer2, h=11)
beerfit2 <- naive(beer2, h=11)
beerfit3 <- snaive(beer2, h=11)

plot(beer2)
plot(beerfit1, plot.conf=FALSE,
  main="Forecasts for quarterly beer production")
lines(beerfit2$mean, col=2)
lines(beerfit3$mean, col=3)
legend("topright",lty=1,col=c(4,2,3),
  legend=c("Mean method","Naive method","Seasonal naive method"))
plot(beerfit3, col=3, plot.conf=FALSE)