R/nng.R

   1 #' Compute the nearest-neighbors graph + pairwise distances.
   2 #'
   3 #' This is just a wrapper around C++/Rcpp function.
   4 #'
   5 #' @param data data.frame or matrix.
   6 #' @param k Number of neighbors at each point.
   7 #' @param mutual Whether or not to build mutual kNN graph.
   8 #'
   9 #' @return A list with $graph and $distances.
  10 #'
  11 #' @export
  12 nng <- function(data, k=ceil(sqrt(nrow(data))), mutual=TRUE)
  13 {
  14   mdata <- data
  15   if (is.data.frame(data)) mdata <- as.matrix(data)
  16   res <- findNeighbors(mdata, k, mutual)
  17   list(graph = igraph::graph_from_edgelist(t(res$edges), directed = !mutual),
  18        distances = sqrt(res$euc_dists))
  19 }