what is xreg how to find seasonality of arma models r error xreg r error when using seasonality error xreg what is double seasonality in r what is the difference between daily seasonality and dummy seasonality? arima seasonality in r r dummy seasonality arima double seasonality which of the following errors arises when you dummy-fit seasonality? arima seasonality with dummy what is xreg? r dummy seasonality how to calculate seasonality in arima when calculating arima double seasonality arima double seasonality with dummy r generate seasonality dummy which error does aima r what is xreg error