Number of differences required for a stationary series

Use a unit root function to determine the minimum number of differences necessary to obtain a stationary time series.

unitroot_ndiffs(x, alpha = 0.05,
  unitroot_fn = ~unitroot_kpss(.)["kpss_pvalue"], differences = 0:2,
  ...)

unitroot_nsdiffs(x, alpha = 0.05, unitroot_fn = ~feat_stl(.,
  .period)[2] < 0.64, differences = 0:2, .period = 1, ...)

Arguments

x	A vector to be tested for the unit root.
alpha	The level of the test.
unitroot_fn	A function (or lambda) that provides a p-value for a unit root test.
differences	The possible differences to consider.
...	Additional arguments passed to the unitroot_fn function
.period	The period of the seasonality.

Value

A numeric corresponding to the minimum required differences for stationarity.