urca (version 1.3-0)

ur.za: Zivot \& Andrews Unit Root Test

Description

Performs the Zivot \& Andrews unit root test, which allows a break at an unknown point in either the intercept, the linear trend or in both.

Usage

ur.za(y, model = c("intercept", "trend", "both"), lag=NULL)

Value

An object of class ur.za.

Arguments

y

Vector to be tested for a unit root.

model

Specification if the potential break occured in either the intercept, the linear trend or in both.

lag

The highest number of lagged endogenous differenced variables to be included in the test regression

Author

Bernhard Pfaff

Details

This test is based upon the recursive estimation of a test regression. The test statistic is defined as the minimum t-statistic of the coeffcient of the lagged endogenous variable.

References

Zivot, E. and Andrews, Donald W.K. (1992), Further Evidence on the Great Crash, the Oil-Price Shock, and the Unit-Root Hypothesis, Journal of Business \& Economic Statistics, 10(3), 251--270.

Download possible at: http://cowles.econ.yale.edu/, see rubric 'Discussion Papers (CFDPs)'.

See Also

ur.za-class

Examples

data(nporg)
gnp <- na.omit(nporg[, "gnp.r"])
za.gnp <- ur.za(gnp, model="both", lag=2)
summary(za.gnp)