我被要求嘗試從ARIMA模型(μ,Φ,θ)中找到參數,我最初認爲它只是ARIMA模型的階數,例如(1,0,1 )(1,1,0)但我的經理說這不是他想要的。ARIMA輸出在r中的定義
我查看了ARIMA模型運行後的總結,發現了phi,theta和delta的值,但有多個值,我非常不確定哪一個是我需要的。
這裏是我發現的值:
M<-matrix(c("08Q1", "08Q2", "08Q3", "08Q4", "09Q1", "09Q2", "09Q3", "09Q4", "10Q1", "10Q2", "10Q3", "10Q4", "11Q1", "11Q2", "11Q3", "11Q4", "12Q1", "12Q2", "12Q3", "12Q4", "13Q1", "13Q2", "13Q3", "13Q4", "14Q1", "14Q2", 79160.56, 91759.73, 91186.48, 106353.82, 70346.47, 80279.15, 82611.60, 131392.72, 93798.99, 105944.78, 103913.13, 154530.69, 110157.40, 117416.09, 127423.42, 156752.00,120097.81, 121307.75, 115021.12, 150657.83, 113711.53, 115353.14, 112701.98, 154319.18,116803.54, 118352.54),ncol=2,byrow=FALSE)
deltaT<-1/4
horiz<-4
startY<-c(8,1)
aslog<-"y"
Nu<-M[,length(M[1,])]
Nu<-as.numeric(Nu)
Nu<-ts(Nu,deltat=deltaT,start=startY)
Mdates<-as.character(M[,1])
if(aslog=="y")
{N<-log(Nu)} else
{N<-Nu}
library(forecast)
library(tseries)
max.sdiff <- 3
arima.force.seasonality <- "n"
suppressWarnings(kpssW <- kpss.test(N, null="Level"))
suppressWarnings(ppW <- tryCatch({ppW <- pp.test(N, alternative = "stationary")}, error = function(ppW) {ppW <- list(error = "TRUE", p.value = 0.99)}))
suppressWarnings(adfW <- adf.test(N, alternative = "stationary", k = trunc((length(N)-1)^(1/3))))
if(kpssW$p.value < 0.05 | ppW$p.value > 0.05 | adfW$p.value > 0.05) {ndiffsW = 1} else {ndiffsW = 0}
aaw <- auto.arima(N, max.D= max.sdiff, d=ndiffsW, seasonal=TRUE,
allowdrift=FALSE, stepwise=FALSE, trace=FALSE, seasonal.test="ch")
orderWA <- c(aaw$arma[1], aaw$arma[6] , aaw$arma[2])
orderWS <- c(aaw$arma[3], aaw$arma[7] , aaw$arma[4])
if(sum(aaw$arma[1:2])==0) {orderWA[1] <- 1} else {NULL}
if(arima.force.seasonality == "y") {if(sum(aaw$arma[3:4])==0) {orderWS[1] <- 1} else {NULL}} else {NULL}
ArimaW1 <- Arima(N, order= orderWA, seasonal=list(order=orderWS), method="ML")
ArimaW1$model
此示出了用於披5個不同的值,4 theta和1德爾塔。我怎麼知道哪個是正確的參數值?或者,我是否全部使用它們來顯示參數,並強制參數在我的數據的截斷版本上測試擬合的準確性?
非常感謝謝謝! – 2014-10-09 08:30:13