  We describe the R package kdecopula (current version 0.9.0), which provides
fast implementations of various kernel estimators for the copula density. Due
to a variety of available plotting options it is particularly useful for the
exploratory analysis of dependence structures. It can be further used for
accurate nonparametric estimation of copula densities and resampling. The
implementation features spline interpolation of the estimates to allow for fast
evaluation of density estimates and integrals thereof. We utilize this for a
fast renormalization scheme that ensures that estimates are bona fide copula
densities and additionally improves the estimators' accuracy. The performance
of the methods is illustrated by simulations.
