lgtm

server-rs/src/data/area_crime_averages.rs

@@ -0,0 +1,47 @@
+//! Precomputed per-outcode and per-postcode-sector average crime rates.
+//!
+//! The right pane shows each crime metric's national average (the global
+//! feature-histogram mean). To let users see how an area compares with its
+//! immediate surroundings, we also precompute the mean headline crime rate
+//! (`"X (avg/yr)"`) across every property in the selection's outcode (e.g.
+//! `"E14"`) and postcode sector (e.g. `"E14 2"`).
+//!
+//! Crime figures are constant within a postcode (the pipeline merges them on
+//! the postcode key), so each postcode's value is read once — from its first
+//! row — and property-weighted by the postcode's row count. That keeps these
+//! averages on the same property-weighted basis as the national average, so the
+//! four numbers (this area / sector / outcode / nation) are directly comparable.
+
+use rustc_hash::FxHashMap;
+
+/// Crime-feature name suffix that marks an annualised headline-rate column
+/// (e.g. `"Burglary (avg/yr)"`). Stripped to derive the bare type name.
+pub const AVG_YR_SUFFIX: &str = " (avg/yr)";
+
+pub struct AreaCrimeAverages {
+    /// Bare crime-type names (suffix stripped, e.g. `"Burglary"`), index-aligned
+    /// with the per-area mean vectors. Matches `CrimeYearStats.name`.
+    pub crime_types: Vec<String>,
+    /// National mean headline rate per crime type (index-aligned with
+    /// `crime_types`). An EXACT property-weighted mean over every postcode, so it
+    /// shares a basis with `by_outcode`/`by_sector` and the per-selection mean —
+    /// unlike the histogram-bin national average, which is biased upward for the
+    /// right-skewed crime densities. `NaN` where no postcode has data.
+    pub national: Vec<f32>,
+    /// Outcode (e.g. `"E14"`) → mean headline rate per crime type. `NaN` where
+    /// the outcode has no data for that type.
+    pub by_outcode: FxHashMap<String, Vec<f32>>,
+    /// Postcode sector (e.g. `"E14 2"`) → mean headline rate per crime type.
+    pub by_sector: FxHashMap<String, Vec<f32>>,
+}
+
+impl AreaCrimeAverages {
+    pub fn empty() -> Self {
+        Self {
+            crime_types: Vec::new(),
+            national: Vec::new(),
+            by_outcode: FxHashMap::default(),
+            by_sector: FxHashMap::default(),
+        }
+    }
+}