prepkit - Data Normalization and Transformation

Provides functions for data normalization and transformation in preprocessing stages. Implements scaling methods (min-max, Z-score, L2 normalization) and power transformations (Box-Cox, Yeo-Johnson). Box-Cox transformation is described in Box and Cox (1964) <doi:10.1111/j.2517-6161.1964.tb00553.x>, Yeo-Johnson transformation in Yeo and Johnson (2000) <doi:10.1093/biomet/87.4.954>.