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2011 Jul 20
0
The C function getQ0 returns a non-positive covariance matrix and causes errors in arima()
...y small, and then, the likelihood computed by KalmanLike is a number (and not NaN). Here is a function allowing to compare the three methods test <- function(phi,theta){ out <- makeARIMA(phi,theta,NULL) Q0bis <- Q0bis(phi,theta) Q0ter <- Q0ter(phi,theta) mod <- out modbis <- out modter <- out modbis$Pn <- Q0bis modter$Pn <- Q0ter set.seed(1) x <- arima.sim(100,model=list(ar=phi,ma=theta)) s <- KalmanLike(x,mod=mod,fast=FALSE) sbis <- KalmanLike(x,modbis) ster <- KalmanLike(x,modter) test12 <- all.equal(out$Pn,Q0b...