I have a simple time series of one hour intervals:
library('forecast')
# load an hourly time series of points
usage <- ts(scan('http://cl.ly/102L0j3o1p2m0m3p0t2o/usage'), frequency = 24)
plot.ts(usage)
the Holt-Winters forecast looks as expected. plot
usage_forecast_hw <- forecast(HoltWinters(usage), h = 168)
# extremely low p-value - 2.2e-16
Box.test(usage_forecast_hw$residuals, lag = 20, type = 'Ljung-Box')
# prediction intervals look as expected.
plot(usage_forecast_hw)
but when I try to use ETS to do the forecast, it comes out flat. plot
# forecast using ets, it uses M, Md, N for model parameters (i'm not sure what Md is)
# AIC = 78323.94
usage_forecast_ets <- forecast(ets(usage), h = 168)
# extremely low p-value - 5.551e-16
Box.test(usage_forecast_ets$residuals, lag = 20, type = 'Ljung-Box')
plot(usage_forecast_ets)
any help would be appreciated