W_sign                  W statistics generator for directional FDR
                        control
W_support               W statistics generator for FDR control
canonicalSVD            singular value decomposition
hittingpoint            hitting point calculator on a given path
normc                   default normalization function for matrix
sk.create               generate split knockoff copies
sk.decompose            make SVD as well as orthogonal complements
sk.filter               Split Knockoff filter for structural sparsity
sk.select               Split Knockoff selector given W statistics
