R/edges.R

In causalDisco: Tools for Causal Discovery on Observational Data

#' List of edges in adjacency matrix
#'
#' Produces a list of edges from an adjacency matrix.
#'
#' @return A list consisting of two lists: One for oriented edges (\code{$dir}),
#' and one for unoriented edges (\code{$undir}).
#'
#' @param amat An adjacency matrix.
#'
#' @keywords internal
#' @noRd
edges_amat <- function(amat) {
  p <- nrow(amat)
  edge_list <- lapply(split(amat, rep(1:p, each = p)), function(x) {
    which(x == 1)
  })

  out <- list()
  for (i in 1:p) {
    children <- edge_list[[i]]
    nchild <- length(children)
    if (nchild > 0) {
      for (j in 1:nchild) {
        out <- c(out, list(c(i, children[j])))
      }
    }
  }
  oneway <- list()
  bothways <- list()
  if (length(out) > 0) {
    revout <- lapply(out, rev)
    bothways <- base::intersect(revout, out)
    if (length(bothways) > 0) {
      oneway <- base::setdiff(out, bothways)
      bothways <- unique(lapply(bothways, sort))
    } else {
      oneway <- out
    }
  }
  list(`dir` = oneway, `undir` = bothways)
}

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