Hns is equal to (4/(n*(d+2*r+2)))^(2/(d+2*r+4))*var(x),
n = sample size, d = dimension of data, r = derivative
order. hns is the analogue of Hns for 1-d data. These
can be used for density (derivative) estimators
kde, kdde.
The equivalents for distribution estimators kcde are
Hns.kcde and hns.cde.
References
Chacon J.E., Duong, T. & Wand, M.P. (2011). Asymptotics for
general multivariate kernel density derivative
estimators. Statistica Sinica. 21, 807-840.