Polar coordinate plot
Charts where angle has meaning — wind direction, compass bearing, time-of-day distributions. v1 ships a wind-rose-style polar bar variant: concentric grid + radial spokes + one filled sector per category, sized to its value.
The demo plots Florence Nightingale's monthly disease deaths in the British Army during the Crimean War, April–November 1854 — the per-month breakdown behind her famous coxcomb diagram in Notes on Matters Affecting the Health, Efficiency, and Hospital Administration of the British Army (1858). The pie chapter shows the aggregate three-category summary; this polar view shows the same data sliced by month — the Sep–Nov peak driven by the Scutari hospital sanitation crisis stands out immediately.
Source: Florence Nightingale — Wikipedia
Public surface
use wisp_chart::polar::{PolarPlot, PolarCoord};
use wisp_chart::color::Color;
let plot = PolarPlot::new(
vec!["N".into(), "NE".into(), "E".into(), "SE".into(),
"S".into(), "SW".into(), "W".into(), "NW".into()],
vec![12.0, 18.0, 22.0, 30.0, 25.0, 16.0, 14.0, 8.0],
);
let g = plot.emit_graphics(&theme, Vec2::new(320.0, 320.0));Coord convention
The polar coord system is exposed via [PolarCoord] for callers
who want to compose their own primitives on a polar layout:
| Angle (rad) | Direction |
|---|---|
0 | Right (+x) |
π/2 | Top (-y screen) |
π | Left (-x) |
3π/2 | Bottom (+y screen) |
PolarCoord::to_pixel(θ, r ∈ [0, 1]) projects to pixel space:
(centre.x + r·cos θ, centre.y − r·sin θ). Screen +y is down,
so sin(θ) is negated to keep "0 = right, π/2 = top" reading.
Sector layout
Sectors start at angle π/2 (top — N on a compass) and go
clockwise through the category list. This matches compass
convention: N → NE → E → … → NW → back to N.
Beyond wind roses
For richer polar marks (lines, points, custom sectors), use
PolarCoord directly to convert your data to pixel positions
and emit wisp::Graphics primitives. The PolarPlot value
type is a ready-baked wind-rose; the coord system underneath is
general.
Related polar charts
For specific polar shapes that have their own constructors and chapter — read them first if your use case fits:
- Pie / donut — categorical proportions filling 2π.
- Sunburst — radial hierarchy across rings.
- Radar — multi-axis polygon overlay.
- Gauge — semicircle indicator with threshold zones.