Find nodes (vertices where degree != 2) — find_nodes • wkpool

Find nodes (vertices where degree != 2)

Usage

find_nodes(x, quotient = FALSE)

Arguments

x: A wkpool (ideally after merge_coincident)
quotient: Count in the quotient graph: duplicated shared boundaries (the same undirected vertex pair carried by more than one feature) count once. A vertex interior to a shared boundary has quotient degree 2 - the degree-2 invariant holds at this level - while true junctions (three or more distinct edges) stay nodes. Default FALSE counts every segment.

Value

Integer vector of .vx IDs that are nodes

Details

Nodes are branch points (degree 3+) or endpoints (degree 1). Degree-2 vertices are pass-through points within an arc.

Examples

x <- wk::as_wkb(c(
  "POLYGON ((0 0, 1 0, 1 1, 0 1, 0 0))",
  "POLYGON ((1 0, 2 0, 2 1, 1 1, 1 0))"
))
pool <- establish_topology(x)
merged <- merge_coincident(pool)
find_nodes(merged)
#> [1] 2 3