The bridge between link and fresh. Takes scored crossings and returns
a list spec that plugs directly into
frs_habitat(break_sources = list(...)). Zero translation needed —
link scores, fresh consumes.
Usage
lnk_break_source(
conn,
crossings,
label = NULL,
label_col = "severity",
label_map = c(high = "blocked", moderate = "potential"),
where = NULL
)Arguments
- conn
A DBI::DBIConnection object (used only for table validation).
- crossings
Character. Schema-qualified scored crossings table (output of
lnk_score_severity()).- label
Character. Static label for all rows (mutually exclusive with
label_col).- label_col
Character. Column to read labels from (default:
"severity"— the columnlnk_score_severity()creates).- label_map
Named character vector. Keys are link severity levels, values are fresh break labels. Default maps high -> blocked, moderate -> potential.
- where
Character. Optional SQL filter (e.g., only crossings in a specific watershed). Developer API — raw SQL, must not contain user input.
Value
A named list with elements table, label or label_col,
label_map, and optionally where — exactly the format
frs_habitat() expects.
Details
Zero-friction bridge: the return value IS a fresh break source spec. No transformation, no adapter — just pass it through.
label_map is the key abstraction: link thinks in severity
(high/moderate/low). fresh thinks in access (blocked/potential/accessible).
The map translates between domains.
Examples
# --- The link -> fresh handoff ---
if (FALSE) { # \dontrun{
conn <- lnk_db_conn()
# Step 1: Score crossings with link
lnk_score_severity(conn, "working.crossings")
# Step 2: Produce break source
src <- lnk_break_source(conn, "working.crossings")
# Returns:
# list(table = "working.crossings",
# label_col = "severity",
# label_map = c(high = "blocked", moderate = "potential"))
# Step 3: Feed to fresh — link's output is fresh's input
frs_habitat(conn, "BULK", break_sources = list(src))
# --- Combine with other break sources ---
frs_habitat(conn, "BULK", break_sources = list(
src,
list(table = "working.falls", label = "blocked"),
list(table = "working.dams", label = "blocked")))
# link scored crossings + falls + dams — all as break sources.
# --- Custom label_map for a conservative project ---
# Only treat high-severity as blocked
src_strict <- lnk_break_source(conn, "working.crossings",
label_map = c(high = "blocked"))
# --- Static label for all crossings ---
src_all <- lnk_break_source(conn, "working.crossings",
label = "potential", label_col = NULL)
# Every crossing is a potential barrier — no severity differentiation.
} # }