Function arma is crashing in some (pathological, but crashing is never good)
cases.
For example:
library(tseries)
arma(c(2.01, 2.22, 2.09, 2.17, 2.42), order=c(1,0))
I came to that pathological series while doing test cases; probably there
are crashing cases with longer series.
Alberto Monteiro