My timeseries comes from the datasets package. It is called "USAccDeaths".
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
1973 9007 8106 8928 9137 10017 10826 11317 10744 9713 9938 9161 8927
1974 7750 6981 8038 8422 8714 9512 10120 9823 8743 9129 8710 8680
1975 8162 7306 8124 7870 9387 9556 10093 9620 8285 8466 8160 8034
1976 7717 7461 7767 7925 8623 8945 10078 9179 8037 8488 7874 8647
1977 7792 6957 7726 8106 8890 9299 10625 9302 8314 8850 8265 8796
1978 7836 6892 7791 8192 9115 9434 10484 9827 9110 9070 8633 9240
When I make an out of sample forcast in GRETL i get the follwoing:
However, when i make the same forecast in R, my results differ subtantially. This is my r code:
library(forecast)
fit <- arima(USAccDeaths[1:60], order = c(1,1,0), method = "ML")
preds <- as.vector(forecast(fit, h = 12))$mean
RMSE <- sqrt(mean((preds - as.vector(USAccDeaths[61:72])) ^ 2))
RMSE
I get an RMSE of 946.024. This is my predictions in R:
[1] 8803.104 8803.199 8803.201 8803.201 8803.201 8803.201 8803.201 8803.201 8803.201
[10] 8803.201 8803.201 8803.201here
What is the problem? How can I get the same results in both programs?