Within-Fold Standardization (Leakage-Free)

Standardizes features using training-fold statistics only. Test-fold features are centered and scaled using the same training-derived parameters.

Usage

standardize_within_fold(X_train, X_test)

Arguments

X_train

Training fold feature matrix

X_test

Test fold feature matrix

Value

A list with:

X_train

Standardized training matrix

X_test

Standardized test matrix (using training means/sds)

means

Training-derived column means

sds

Training-derived column SDs (zeros replaced with 1)