Stacked, horizontal, floating and highlighted bars¶

use ironlab::prelude::*;

pub const TITLE: &str = "Stacked, horizontal, floating and highlighted bars";
pub const DESCRIPTION: &str = "Four ways of drawing bars, each in its own axes. The stacked bars are the annual \
     heat balance of four zones of a building: the gains stack upwards from zero and the losses downwards, each part \
     an ordinary bar series whose bases are the running totals of the parts before it, so that the heating each zone \
     needs is what closes its balance and the two stacks of a zone are equally long. A legend panel under the axes, \
     in a row fitted to its entries, keys the five parts. The horizontal bars give the mean downtime per failure of \
     six subsystems of a wind turbine, laid flat so that their long names read level, with the first subsystem at \
     the top. The floating bars show the range over which six substances are liquid at atmospheric pressure: each \
     bar starts at the melting point, its base, and is as long as the difference between the boiling and melting \
     points, its value. The last axes compares the specific strength of six structural materials, the tensile \
     strength divided by the density, with per-bar colours that draw every bar grey except carbon-fibre composite. \
     The names under both lower axes are turned by 30° so that they do not collide.";

/// The zones of the building, with their annual solar and internal gains and their fabric and ventilation losses,
/// in megawatt hours. The heating closes the balance.
const ZONES: [(&str, f64, f64, f64, f64); 4] = [
    ("Offices", 18.0, 26.0, 38.0, 22.0),
    ("Workshop", 6.0, 41.0, 52.0, 35.0),
    ("Store", 2.0, 4.0, 21.0, 9.0),
    ("Atrium", 31.0, 5.0, 44.0, 12.0),
];

/// The subsystems of a wind turbine and their mean downtime per failure, in days.
const SUBSYSTEMS: [(&str, f64); 6] = [
    ("Gearbox planetary stage", 18.5),
    ("Generator bearings and slip rings", 11.0),
    ("Main shaft bearing", 14.2),
    ("Pitch system hydraulics", 3.4),
    ("Power converter modules", 4.8),
    ("Yaw drive and brakes", 2.6),
];

/// Substances with their melting and boiling points at atmospheric pressure, in degrees Celsius.
const LIQUID_RANGES: [(&str, f64, f64); 6] = [
    ("Nitrogen", -210.0, -195.8),
    ("Ammonia", -77.7, -33.3),
    ("Ethanol", -114.1, 78.4),
    ("Water", 0.0, 100.0),
    ("Bromine", -7.2, 58.8),
    ("Mercury", -38.8, 356.7),
];

/// Structural materials with their tensile strength in megapascals and their density in kilograms per cubic metre.
const MATERIALS: [(&str, f64, f64); 6] = [
    ("Steel S355", 510.0, 7850.0),
    ("Aluminium 7075", 570.0, 2810.0),
    ("Titanium 6Al-4V", 950.0, 4430.0),
    ("Carbon fibre", 600.0, 1550.0),
    ("Glass fibre", 400.0, 1900.0),
    ("Douglas fir", 85.0, 530.0),
];

/// The material that the last axes highlights.
const HIGHLIGHTED: &str = "Carbon fibre";

pub fn figure() -> Figure {
    let mut fig = Figure::new()
        .size_mm(180.0, 150.0)
        .tiles(3, 2)
        .fit_row(1)
        .title("Four ways of drawing bars")
        .tag("bar")
        .tag("line")
        .tag("subplots")
        .tag("legend")
        .tag("categorical")
        .tag("ticks")
        .tag("stacked")
        .tag("horizontal")
        .tag("floating")
        .tag("highlighted")
        .tag("tick-angle")
        .tag("engineering")
        .parameter("dimensionality", "2D")
        .parameter("artists", 9)
        .parameter("data_points", 96)
        .parameter("has_legend", true);

    // The heat balance: gains above zero, losses below, and the heating that closes the balance of each zone. Its key
    // is a legend panel under the axes, in a row fitted to its entries.
    let zones: Vec<f64> = (0..ZONES.len()).map(|k| k as f64).collect();
    let column = |pick: fn(&(&str, f64, f64, f64, f64)) -> f64| -> Vec<f64> { ZONES.iter().map(pick).collect() };
    let solar = column(|z| z.1);
    let internal = column(|z| z.2);
    let heating = column(|z| z.3 + z.4 - z.1 - z.2);
    let fabric = column(|z| -z.3);
    let ventilation = column(|z| -z.4);
    let key = fig.panel(1, 0).legend().boxed(false).id();
    let mut ax = fig.axes(0, 0);
    ax.bars(&zones)
        .stacked("balance", "Solar gains", solar)
        .stacked("balance", "Internal gains", internal)
        .stacked("balance", "Heating", heating)
        .stacked("balance", "Fabric losses", fabric)
        .stacked("balance", "Ventilation losses", ventilation);
    ax.hline(0.0).color(Color::BLACK).line_width(0.5);
    ax.xcategories(ZONES.map(|z| z.0))
        .ylabel("Annual heat (MWh)")
        .title("Stacked: a heat balance")
        .legend_in(key);

    // The downtime of each subsystem, laid flat so that the long names read level.
    let rows: Vec<f64> = (0..SUBSYSTEMS.len()).map(|k| k as f64).collect();
    let mut ax = fig.axes_span(0, 1, 2, 1);
    ax.barh(&rows, SUBSYSTEMS.map(|s| s.1))
        .face_color(Color::rgb(0.30, 0.47, 0.66));
    ax.ycategories(SUBSYSTEMS.map(|s| s.0))
        .xlabel("Mean downtime per failure (days)")
        .title("Horizontal: long category names");

    // The liquid range of each substance: a bar from its melting point, as long as the range.
    let substances: Vec<f64> = (0..LIQUID_RANGES.len()).map(|k| k as f64).collect();
    let melting = LIQUID_RANGES.map(|s| s.1);
    let range = LIQUID_RANGES.map(|s| s.2 - s.1);
    let mut ax = fig.axes(2, 0);
    ax.bar(&substances, range)
        .base_data(melting)
        .face_color(Color::rgb(0.35, 0.65, 0.85));
    ax.xcategories(LIQUID_RANGES.map(|s| s.0))
        .xtick_label_angle(30.0)
        .ylabel(r"Temperature ($^\circ$C)")
        .title("Floating: liquid at 1 atm");

    // The specific strength of each material, with every bar grey but the highlighted one.
    let materials: Vec<f64> = (0..MATERIALS.len()).map(|k| k as f64).collect();
    let strength = MATERIALS.map(|m| m.1 / m.2 * 1.0e3);
    let grey = Color::rgb(0.65, 0.65, 0.65);
    let red = Color::rgb(0.80, 0.15, 0.10);
    let colors = MATERIALS.map(|m| if m.0 == HIGHLIGHTED { red } else { grey });
    let mut ax = fig.axes(2, 1);
    ax.bar(&materials, strength).colors(colors);
    ax.xcategories(MATERIALS.map(|m| m.0))
        .xtick_label_angle(30.0)
        .ylabel(r"Specific strength (kN$\,$m/kg)")
        .title("Per-bar colours: one highlighted");
    fig
}