Nested-set upstream index for a hydrofabric (flowpath + nexus grain)

Resolves the `flowpath -> nexus -> flowpath` topology to a direct flowpath graph and runs [upstream_index()] over it. Shared by [write_hydrofabric()] so a hydrofabric is indexed the same way however it is written. A divergent nexus (two downstreams) is flagged; the index is exact only on a rooted tree.

Usage

hf_upstream_index(
  flowpaths,
  nexus = NULL,
  fp_id = "flowpath_id",
  fp_toid = "flowpath_toid",
  nex_id = "nexus_id",
  nex_toid = "nexus_toid"
)

Arguments

flowpaths

Data frame with `flowpath_id` and `flowpath_toid`.

nexus

Data frame with `nexus_id` and `nexus_toid`, or `NULL` (a `flowpath_toid` that is not a flowpath is then a terminal).

fp_id, fp_toid

Flowpath id / downstream column names.

nex_id, nex_toid

Nexus id / downstream column names.

Value

A data frame with `flowpath_id`, `upstream_id`, `num_upstreams` aligned to `flowpaths` (attributes `n_outlets`, `n_divergences`, `n_bad`).

See also

Other network properties: accumulate_downstream(), get_hydroseq(), get_levelpath(), get_pathlength(), get_pfafstetter(), get_streamlevel(), get_streamorder(), merge_groups(), upstream_index()

Examples

fp  <- data.frame(flowpath_id = c("1","2","3"), flowpath_toid = c("nex-9","0","nex-9"))
nex <- data.frame(nexus_id = "nex-9", nexus_toid = "2")
hf_upstream_index(fp, nex)
#>   flowpath_id upstream_id num_upstreams
#> 1           1           3             0
#> 2           2           1             2
#> 3           3           2             0