rkevinbur...@charter.net wrote:
I was looking at the 'R' code associated with arima. I see the following:
upARIMA <- function(mod, phi, theta) {
p <- length(phi)
q <- length(theta)
mod$phi <- phi
mod$theta <- theta
r <- max(p, q + 1)
if (p > 0)
mod$T[1:p, 1] <- phi
if (r > 1)
mod$Pn[1:r, 1:r] <- .Call(R_getQ0, phi, theta)
else if (p > 0)
mod$Pn[1, 1] <- 1/(1 - phi^2)
else mod$Pn[1, 1] <- 1
mod$a[] <- 0
mod
}
In particular the statement:
else if (p > 0)
mod$Pn[1, 1] <- 1/(1 - phi^2)
....
So I was wondering if there is something that I am missing that will
"guarantee" that the length of the phi vector in this case is always 1.
There is. You are only getting there if r > 1 is FALSE, and by the
definition of r, that can only happen if q==0 and (p==0 or p==1).
--
O__ ---- Peter Dalgaard Øster Farimagsgade 5, Entr.B
c/ /'_ --- Dept. of Biostatistics PO Box 2099, 1014 Cph. K
(*) \(*) -- University of Copenhagen Denmark Ph: (+45) 35327918
~~~~~~~~~~ - (p.dalga...@biostat.ku.dk) FAX: (+45) 35327907
______________________________________________
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
