Shared legend panel¶

use std::f64::consts::PI;

use ironlab::prelude::*;

pub const TITLE: &str = "Shared legend panel";
pub const DESCRIPTION: &str = "Three days of synthetic hourly readings from five weather stations, with one legend \
     panel, titled \"Key\", in the sixth tile. Every station plots its air temperature and dew point, and the three coastal stations \
     also plot the sea surface temperature. Entries with the same display name and the same look are listed once, so \
     the panel holds three entries for thirteen series; in the viewer, clicking an entry hides that series in every \
     axes.";

const AIR: Color = Color::rgb(0.80, 0.24, 0.16);
const DEW_POINT: Color = Color::rgb(0.13, 0.40, 0.70);
const SEA: Color = Color::rgb(0.10, 0.55, 0.50);

/// Each station's name, the mean and the daily range of its air temperature, and the temperature of the sea beside
/// it if it is on the coast, in degrees Celsius.
const STATIONS: [(&str, f64, f64, Option<f64>); 5] = [
    ("Lerwick", 10.0, 3.0, Some(11.5)),
    ("Inverness", 13.0, 7.0, Some(12.5)),
    ("Aberdeen", 12.5, 6.0, Some(12.0)),
    ("Braemar", 11.0, 11.0, None),
    ("Eskdalemuir", 12.0, 9.0, None),
];

pub fn figure() -> Figure {
    let hours = linspace(0.0, 72.0, 73);
    // A cold front passes on the second day and lowers every temperature by up to 3 °C.
    let front: Vec<f64> = hours
        .iter()
        .map(|t| -1.5 * (1.0 + ((t - 36.0) / 4.0).tanh()))
        .collect();

    let mut fig = Figure::new()
        .size_mm(160.0, 150.0)
        .tiles(3, 2)
        .title("Temperatures at five weather stations")
        .tag("line")
        .tag("subplots")
        .tag("legend")
        .tag("dashes")
        .tag("measurements")
        .parameter("dimensionality", "2D")
        .parameter("artists", 13)
        .parameter("data_points", 1898)
        .parameter("has_legend", true);
    // The sixth tile holds the legend panel that every axes lists its entries in.
    let key = fig.panel(2, 1).title("Key").id();

    for (k, (name, mean, range, sea)) in STATIONS.into_iter().enumerate() {
        // The air is warmest at 15:00 and coolest at 03:00, when it cools to just above the dew point.
        let air: Vec<f64> = hours
            .iter()
            .zip(&front)
            .map(|(t, front)| mean + front + range / 2.0 * (2.0 * PI * (t - 9.0) / 24.0).sin())
            .collect();
        let dew_point: Vec<f64> = front
            .iter()
            .map(|front| mean - range / 2.0 - 0.5 + front)
            .collect();

        let mut ax = fig.axes(k as u32 / 2, k as u32 % 2);
        // The same display name and the same look in every axes make one entry in the panel.
        ax.plot(&hours, &air)
            .label("Air temperature")
            .color(AIR);
        ax.plot(&hours, &dew_point)
            .label("Dew point")
            .color(DEW_POINT)
            .dash(Dash::Dashed);
        if let Some(sea) = sea {
            ax.plot(&hours, vec![sea; hours.len()])
                .label("Sea surface temperature")
                .color(SEA)
                .dash(Dash::Dotted);
        }
        ax.title(name)
            .xlabel("Time (h)")
            .ylabel("Temperature (°C)")
            .xlim(0.0, 72.0)
            .ylim(0.0, 20.0)
            .grid(true)
            .legend_in(key);
    }
    fig
}