ndiffs {forecast} | R Documentation |
Uses a unit root test to determine the number of differences required for time series x
. If test="kpss"
,
the KPSS test is used with the null hypothesis that x
has a stationary root against a unit-root alternative. Then the test returns
the least number of differences required to pass the test at the level alpha
. If test="adf"
, the Augmented Dickey-Fuller test is used
with the null hypothesis that x
has a unit root against a stationary root alternative. Then the test returns the least number of differences
required to fail the test at the level alpha
.
ndiffs(x, alpha=0.05, test=c("kpss","adf"))
x |
A univariate time series |
alpha |
Level of the test |
test |
Type of unit root test to use |
An integer.
Rob J Hyndman
ndiffs(WWWusage)