Hello, I am using the ur.df function from the {arca} package to run the augmented Dickey-Fuller unit root test on several time series. However; I do not understand the econometric interpretation of the the "phi1" and "phi2" test-statisitc which are output if you choose a "trend" or "drift" model. I looked at the source code for the function but I do not quite understand the code (which I have included below). Any help would be much appreciate.
Thanks, Max if (type == "drift") { result <- lm(z.diff ~ z.lag.1 + 1) phi1.reg <- lm(z.diff ~ -1) phi1 <- anova(phi1.reg, result)$F[2] tau <- coef(summary(result))[2, 3] teststat <- as.matrix(t(c(tau, phi1))) colnames(teststat) <- c("tau2", "phi1") } if (type == "trend") { result <- lm(z.diff ~ z.lag.1 + 1 + tt) phi2.reg <- lm(z.diff ~ -1) phi3.reg <- lm(z.diff ~ 1) phi2 <- anova(phi2.reg, result)$F[2] phi3 <- anova(phi3.reg, result)$F[2] tau <- coef(summary(result))[2, 3] teststat <- as.matrix(t(c(tau, phi2, phi3))) colnames(teststat) <- c("tau3", "phi2", "phi3") [[alternative HTML version deleted]] ______________________________________________ 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.