workfile arma u 1 100
series e = 0
series arima1=0
series arima2=0
series arima3=0

rndseed 2222222
series e=nrnd
smpl 3 100
series arima1=0.7+1*arima1(-1)+e
series arima2=-0.7+1*arima2(-1)+e
series arima3=2*arima3(-1) - 1*arima3(-2)+e