library(urca) data(Raotbl3) attach(Raotbl3) lc <- ts(lc, start=c(1966,4), end=c(1991,2), frequency=4) lc.ct <- ur.df(lc, lags=3, type='trend') plot(lc.ct) lc.co <- ur.df(lc, lags=3, type='drift') lc2 <- diff(lc) lc2.ct <- ur.df(lc2, type='trend', lags=3)