### Simulate the three models in Problem 2.7 and save them.

par(mfrow=c(2,3))

x <- arima.sim(100,model=list(ar=.6,ma=-.9))
write(x, file="E:\\Stat207\\Homework\\Ch2\\Problem2.8\\data1.dat", ncolumns=1, append=F)
tsplot(x,main="ARMA(1,1), ar = .6, ma = .9")
acf(x, 20)
acf(x, 20, "partial")

x <- arima.sim(200,model=list(ar=.6))
write(x, file="E:\\Stat207\\Homework\\Ch2\\Problem2.8\\data2.dat", ncolumns=1, append=F)
tsplot(x,main="ARMA(1,0), ar = .6")
acf(x, 20)
acf(x, 20, "partial")

par(mfrow=c(2,3))

x <- arima.sim(200,model=list(ma=-.9))
write(x, file="E:\\Stat207\\Homework\\Ch2\\Problem2.8\\data3.dat", ncolumns=1, append=F)
tsplot(x,main="ARMA(0,1), ma = .9")
acf(x, 20)
acf(x, 20, "partial")