Dear all, I would like to fit an ARMA model, but I'm not sure exactly how to fit it. Here's an example of the problem. This is my time variable, hourly data t <- seq(as.POSIXct("2011-01-01 00:00:00"), as.POSIXct("2011-12-31 23:00:00"), by="hour") my response y <- rnorm(length(t), 1000, 500) seasonal factors: t.h <- as.POSIXlt(t)$hour # hours of the day t.d <- as.POSIXlt(t)$day # days of the week t.m <- as.POSIXlt(t)$mon # months of the year this is my regressor x.reg <- rnorm(length(t), 10, 1) and I have the following auto-regressive lags (1 to 10, 24, and 48 hours) y.lag1 <- lag(y, 1) y.lag2 <- lag(y, 2) y.lag3 <- lag(y, 3) y.lag4 <- lag(y, 4) y.lag5 <- lag(y, 5) y.lag6 <- lag(y, 6) y.lag7 <- lag(y, 7) y.lag8 <- lag(y, 8) y.lag9 <- lag(y, 9) y.lag10 <- lag(y, 10) y.lag24 <- lag(y, 24) y.lag48 <- lag(y, 48) I want to fit an ARMA with my 3 seasonal factors, 12 lagged variables and the regressor against my response variable. Does someone know how such an ARMA model can be fit? Thank you for your help. Regards, Dave [[alternative HTML version deleted]]