findnds: Identify the next downstream site from a set of candidates
In nickbond/catchstats: Tools for manipulating nested catchment datasets

Description Usage Arguments Value Note Examples

Identify the next downstream site from a set of candidates

1	findnds(hierarchy, catchname, candidates)

`hierarchy`	a dataframe containing catchment id and next downstream (nextds) id fields
`catchname`	a catchment id for which a a list of downstream catchments ids will be returned.
`candidates`	a vector of candidate catchment ids. Note this need not be a complete hierarchy

a list of downstream catchment ids for each catchment in catchnames. Returns -1 where there is no downstream site

Function depends on the next downstream field in a stream network 'hierarchy' table (dataframe). Can be used to support further aggregation of environmental variables for sub-catchments downstream of a list of catchments of interest (e.g. for calculating barrier numbers).

data(mwcats)

#find site next downstream of the first site in the catchment list

findnds(hierarchy = mwcats[,c(1:2)], catchname = mwcats$site[1], candidates=mwcats$site)