tmpyr {arfima} | R Documentation |
Temperature Data
Description
Central England mean yearly temperatures from 1659 to 1976
Format
A ts tmpyr
Details
Hosking notes that while the ARFIMA(1, d, 1) has a lower AIC, it is not much lower than the AIC of the ARFIMA(1, d, 0).
Bhansali and Kobozka find: muHat = 9.14, d = 0.28, phi = -0.77, and theta =
-0.66 for the ARFIMA(1, d, 1), which is close to our result, although our
result reveals trimodality if numeach
is large enough. The third
mode is close to Hosking's fit of an ARMA(1, 1) to these data, while the
second is very antipersistent.
Our package gives a very close result to Hosking for the ARFIMA(1, d, 0)
case, although there is also a second mode. Given how close it is to the
boundary, it may or may not be spurious. A check with dmean = FALSE
shows that it is not the optimized mean giving a spurious mode.
If, however, we use whichopt = 1
, we only have one mode. Note that
Nelder-Mead sometimes does take out non-spurious modes, or add spurious
modes to the surface.
Source
https://hadleyserver.metoffice.gov.uk/hadobs/hadcet/
References
Parker, D.E., Legg, T.P., and Folland, C.K. (1992). A new daily Central England Temperature Series, 1772-1991. Int. J. Clim., Vol 12, pp 317-342
Manley,G. (1974). Central England Temperatures: monthly means 1659 to 1973. Q.J.R. Meteorol. Soc., Vol 100, pp 389-405.
Hosking, J. R. M. (1984). Modeling persistence in hydrological time series using fractional differencing, Water Resour. Res., 20(12)
Bhansali, R. J. and Koboszka, P. S. (2003) Prediction of Long-Memory Time Series In Doukhan, P., Oppenheim, G. and Taqqu, M. S. (Eds) Theory and Applications of Long-Range Dependence (pp355-368) Birkhauser Boston Inc.
Veenstra, J.Q. Persistence and Antipersistence: Theory and Software (PhD Thesis)
Examples
data(tmpyr)
fit <- arfima(tmpyr, order = c(1, 0, 1), numeach = c(3, 3), dmean = TRUE, back=TRUE)
fit
##suspect that fourth mode may be spurious, even though not close to a boundary
##may be an induced mode from the optimization of the mean
fit <- arfima(tmpyr, order = c(1, 0, 1), numeach = c(3, 3), dmean = FALSE, back=TRUE)
fit
##perhaps so
plot(tacvf(fit), maxlag = 30, tacf = TRUE)
fit1 <- arfima(tmpyr, order = c(1, 0, 0), dmean = TRUE, back=TRUE)
fit1
fit2 <- arfima(tmpyr, order = c(1, 0, 0), dmean = FALSE, back=TRUE)
fit2 ##still bimodal. Second mode may or may not be spurious.
fit3 <- arfima(tmpyr, order = c(1, 0, 0), dmean = FALSE, whichopt = 1, numeach = c(3, 3))
fit3 ##Unimodal. So the second mode was likely spurious.
plot(tacvf(fit2), maxlag = 30, tacf = TRUE)
##maybe not spurious. Hard to tell without visualizing the surface.
##compare to plotted tacf of fit1: looks alike
plot(tacvf(fit1), maxlag = 30, tacf = TRUE)
tacfplot(list(fit1, fit2))