Compute Access Breaks at a Gradient Threshold

Find gradient-based access breaks and append break points from external sources (e.g. falls, crossings, dams). This is the expensive step in the habitat pipeline — fwa_slopealonginterval() runs on every blue line key. Species that share the same access_gradient_max can reuse the same breaks table, avoiding redundant computation.

Usage

frs_habitat_access(
  conn,
  table,
  threshold,
  to = "working.breaks_access",
  break_sources = NULL
)

Arguments

conn

A DBI::DBIConnection object (from frs_db_conn()).

table

Character. Working schema table with the stream network (from frs_extract()).

threshold

Numeric. Access gradient threshold (e.g. 0.15 for 15%).

to

Character. Destination table for break points. Default "working.breaks_access".

break_sources

List of break source specs, or NULL to skip external sources (gradient-only). Each spec is a list with:

table

Schema-qualified table name with blue_line_key and downstream_route_measure columns.

where

SQL predicate to filter rows (optional).

label

Static label string for all rows (optional).

label_col

Column name to read labels from (optional).

label_map

Named character vector mapping label_col values to output labels (optional).

Value

conn invisibly, for pipe chaining.

See also

Other habitat: frs_aggregate(), frs_break(), frs_break_apply(), frs_break_find(), frs_break_validate(), frs_categorize(), frs_classify(), frs_col_generate(), frs_col_join(), frs_extract(), frs_habitat(), frs_habitat_partition(), frs_habitat_species()

Examples

if (FALSE) { # \dontrun{
conn <- frs_db_conn()

# Gradient-only (no external break sources)
frs_habitat_access(conn, "working.streams_bulk", threshold = 0.15,
  to = "working.breaks_access_bulk_015")

# With falls and PSCIS crossings
frs_habitat_access(conn, "working.streams_bulk", threshold = 0.15,
  to = "working.breaks_access_bulk_015",
  break_sources = list(
    list(table = "working.falls", where = "barrier_ind = TRUE",
         label = "blocked"),
    list(table = "working.pscis",
         label_col = "barrier_status",
         label_map = c("BARRIER" = "blocked",
                       "POTENTIAL" = "potential"))
  ))

DBI::dbDisconnect(conn)
} # }