Computes various measures based on partial autocorrelation coefficients of the original series, firstdifferenced series and seconddifferenced series.
feat_pacf(x, .period = 1, lag_max = NULL, ...)
x  a univariate time series 

.period  The seasonal period (optional) 
lag_max  maximum lag at which to calculate the acf. The default is

...  Further arguments passed to 
A vector of 3 values: Sum of squared of first 5 partial autocorrelation coefficients of the original series, first differenced series and twicedifferenced series. For seasonal data, the partial autocorrelation coefficient at the first seasonal lag is also returned.