#4
data(airpass)
plot(airpass,type='o')
 points(y=airpass,x=time(airpass),pch=as.vector(season(airpass)))
plot(log(airpass),type='o')
plot(diff(log(airpass)),type='o')
plot(diff(airpass)/zlag(airpass)[-1],type='o')


#5

data(gold)
plot(gold,type='o')
plot(diff(log(gold)),type='o')
acf(diff(log(gold)))

#6

data(deere3)
plot(deere3,type='o')
 acf(deere3)
 pacf(deere3)
 eacf(deere3)


#7

data(robot)
plot(robot,type='o')
 acf(robot)
 pacf(robot)
 eacf(robot)

res=armasubsets(y=robot,nar=8,nma=8,y.name='robot',ar.method='ols')
plot(res)


plot(diff(robot),type='o')
 acf(diff(robot))
 pacf(diff(robot))
 eacf(diff(robot))

res=armasubsets(y=diff(robot),nar=8,nma=8,y.name='diffs',ar.method='ols')
plot(res)