risdr - Regularised and Information-Theoretic Sufficient Dimension
Reduction
Implements covariance-stabilised sufficient dimension
reduction for continuous responses, with an additional sparse
engine for continuous, categorical, and right-censored survival
responses and information-theoretic structural dimension
selection. Supported methods include sliced inverse regression,
sliced average variance estimation, directional regression, and
principal Hessian directions. Sample, ridge, Oracle
Approximating Shrinkage, Ledoit-Wolf, and Maximum Entropy
Covariance (MEC) estimators are provided alongside prediction,
resampling, simulation, and diagnostic utilities. The
sufficient dimension reduction methods build on Li (1991)
<doi:10.1080/01621459.1991.10475035>, Li (1992)
<doi:10.1080/01621459.1992.10476258>, and Li and Wang (2007)
<doi:10.1198/016214507000000536>. Covariance shrinkage follows
Olorede and Yahya (2019) <doi:10.48550/arXiv.1909.13017>,
Ledoit and Wolf (2004) <doi:10.1016/S0047-259X(03)00096-4> and
Chen et al. (2010) <doi:10.1109/TSP.2010.2053029>.