void setAnnotations(Rcpp::Matrix<REALSXP> annotations) {
annotations_ = annotations;
num_annotations_ = annotations.nrow();
assert(annotations.ncol() == D_);
}
inline Mat< CType(RType) > asMat(Rcpp::Matrix<RType>& m){
return Mat< CType(RType) >(m.begin(), m.nrow(), m.ncol());
}