internal functions from Dr. Tibshirani's software package GSA

Description

internal functions from Dr. Tibshirani's software package GSA

References

Bair, Eric, Trevor Hastie, Debashis Paul, and Robert Tibshirani. Prediction by Supervised Principal Components.Journal of the American Statistical Association 101, no. 473 (March 2006): 119-137. doi:10.1198/016214505000000628.