nearest_neighbor_search searches for the k nearest neighbors of a set of
query points.
nearest_neighbor_search(distances, k, query_indices = NULL,
search_indices = NULL, radius = NULL)A distances object.
The number of neighbors to search for.
An integer vector with point indices to query. If NULL,
all data points in distances are queried.
An integer vector with point indices to search among. If NULL,
all data points in distances are searched over.
Restrict the search to a fixed radius around each query. If fewer than k
search points exist within this radius, no neighbors are reported (indicated by NA).
A matrix with point indices for the nearest neighbors. Columns in this matrix indicate queries, and rows are ordered by distances from the query.