library(TSA)
data(airmiles)
?airmiles
plot((airmiles),ylab='(airmiles)',xlab='Year', )

plot(log(airmiles),ylab='Log(airmiles)',xlab='Year', )

?filter
S=c(rep(0,2),rep(1,108))
# step pulse of the post-intervention period
plot(ts(S),type='p')
abline(h=0)

omega=-1
delta=.9
m=filter(x=omega*S, filter=c(delta),method='recursive')
plot(ts(m),type='p',main='change in the mean function due to intervention at T=3')