lnk_thresholds: configurable scoring defaults #3

lnk_thresholds() — configurable scoring defaults

Load, merge, and return severity scoring thresholds as a named list. This is the configuration backbone — every scoring function reads from it.

Signature

lnk_thresholds(
  csv = NULL,
  high = list(outlet_drop = 0.6, slope_length = 120),
  moderate = list(outlet_drop = 0.3),
  low = list()
)

Parameters

All parameters have sane defaults for BC fish passage. Users in other jurisdictions override via csv or named arguments — no code changes needed.

• csv — path to CSV with columns severity, metric, value. Overrides in-code defaults when provided. Same pattern as frs_params(csv = ...).
• high, moderate, low — named lists of metric thresholds. Merged with CSV values (CSV wins on conflict).

Returns

Named list keyed by severity level, each containing metric thresholds:

list(
  high = list(outlet_drop = 0.6, slope_length = 120),
  moderate = list(outlet_drop = 0.3),
  low = list()
)

Design intent

• System-agnostic: metric names are user-defined strings, not hardcoded PSCIS columns
• Composable: output feeds directly into lnk_score_severity(thresholds = lnk_thresholds(...))
• Discoverable: ships inst/extdata/thresholds_default.csv so users can see and copy the format
• Familiar: follows frs_params() pattern — CSV or code, same output shape

Examples must show

1. Default usage (zero-config BC case)
2. CSV override for a project with custom thresholds
3. Inline override for a single metric (lnk_thresholds(high = list(outlet_drop = 0.8)))
4. How output plugs into lnk_score_severity() — show the integration, not just the function in isolation
5. The bundled CSV format so users know what to produce

File layout

• R/lnk_thresholds.R
• tests/testthat/test-lnk_thresholds.R
• inst/extdata/thresholds_default.csv

Relates to #1