Fiedler ordering from a kNN graph — fiedler

Builds a kNN graph on rows of X, computes a 1D ordering coordinate using the Fiedler direction of a normalized graph operator, and returns an ordering t scaled to \([0,1]\).

fiedler_ordering(
  X,
  k = 15,
  weight = c("binary", "rbf", "inv"),
  sigma = NULL,
  keep = c("giant", "all"),
  return_full = TRUE
)

Arguments

X: Numeric matrix \(n \times D\) (rows are observations).
k: Number of nearest neighbors.
weight: Similarity type: "rbf", "inv", or "binary".
sigma: Bandwidth for weight="rbf"; if NULL, uses median kNN distance.
keep: Component handling: "giant" keeps the largest connected component; "all" uses all nodes (may be unstable if disconnected).
return_full: If TRUE (default), return t of length \(n\) with NA for nodes excluded by keep="giant". If FALSE, return t only for the kept nodes.

Value

A list with t, keep_idx, and n_components.