IB                      Spreading measure based on Moran's I index
distUnitk               Squared Euclidean distances of the unit k.
sb_vk                   Values v_k to compute the Spatial balance
varHAJ                  Hajek-Rosen variance estimator
wave                    Weakly associated vectors sampling
wpik                    Stratification matrix from inclusion
                        probabilities
wpikInv                 Stratification matrix from inverse inclusion
                        probabilities
