How to calculate ARIMA(1,0,1)

#1
Hello,
I want to forecast the 101th data of a time series and my data is as follow
99) 0.96
100) -0.2495
101) ?

and my model Coefficients:
ar1 ma1 intercept
0.6769 -0.4255 0.0019
s.e. 0.1210 0.1505 0.0876

By using R I know answer is 0.084036 but I cant get the same answer with my own calculation I have problem specially with MA part. How can we forecast the 101th term?
 

vinux

Dark Knight
#2
If you don't have the residual information, you need complete time series information to generate the forecast. If you are looking for an approximate forecast value you could generate using two lags and the approximation become better as the lag increases.