Hylleberg et. al (1990,pp.226-227) offer simulated critical values for seasonal unitr to test. interpolpval() is an internal call and should not be used independently.
interpolpval(code, stat, N, swarn = TRUE)
Table for critical value and p-value.
Type of HEGY model, this will be automatically identified.
Empirical test statistics.
Sample size calculating stat above.
Logical. Whether the warning message for negative p-value will be returned? The default is TRUE.
Ho Tsung-wu <tsungwu@ntnu.edu.tw>, modifed from Javier Lopez-de-Lacalle
Hylleberg, S., Engle, R.F., Granger, C.W.J., and Yoo, B.S.(1990) Seasonal integration and cointegration. Journal of Econometrics,44, 215-238.
Javier Lopez-de-Lacalle in https://github.com/cran/uroot/blob/master/R/hegy.R