Compute and add Strahler stream order to a directed acyclic network

Native replacement for `hydroloom::add_streamorder` – same topological approach as [get_hydroseq()] (igraph topo-sort), with no external dependency and no non-dendritic/divergence handling required. Leaves are order 1; at each node the order is the max of its upstream contributors, incremented by 1 when that max is shared by two or more of them (Strahler).

Usage

get_streamorder(x, id = "flowpath_id", toid = "flowpath_toid")

Arguments

x

A data frame with the identifier column `id` and downstream pointer `toid`. Terminal/outlet rows use `NA`, `""`, `"0"`, or a `toid` that is not a known `id`.

id, toid

Column names. Default `"flowpath_id"` / `"flowpath_toid"`.

Value

Integer vector of stream orders aligned to the rows of `x`.

Examples

# two headwaters (1,2) join at 3 -> outlet: 3 is order 2
get_streamorder(data.frame(flowpath_id = c("1", "2", "3"),
  flowpath_toid = c("3", "3", "0")))
#> [1] 1 1 2