Shared y limits¶

use ironlab::prelude::*;

pub const TITLE: &str = "Shared y limits";
pub const DESCRIPTION: &str = "Temperature profiles against depth at three sites, side by side in axes whose y limits \
     are all linked with a single call, so that equal depths stay level when any panel is panned or zoomed.";

/// Returns the water temperature in °C at a depth in metres: a smooth thermocline, about 12 m thick, between warm
/// surface water and 4 °C deep water.
fn temperature_c(depth_m: f64, surface_temperature_c: f64, thermocline_depth_m: f64) -> f64 {
    let deep_temperature_c = 4.0;
    let thickness_m = 12.0;
    deep_temperature_c
        + (surface_temperature_c - deep_temperature_c)
            / (1.0 + ((depth_m - thermocline_depth_m) / thickness_m).exp())
}

pub fn figure() -> Figure {
    let depth_m = linspace(0.0, 200.0, 81);
    // Each site is (tile column, name, surface temperature in °C, thermocline depth in m).
    let sites = [
        (0, "Site A", 18.0, 40.0),
        (1, "Site B", 22.0, 60.0),
        (2, "Site C", 12.0, 25.0),
    ];

    let mut fig = Figure::new()
        .size_mm(160.0, 80.0)
        .tiles(1, 3)
        .title("Temperature profiles");
    for (col, name, surface_temperature_c, thermocline_depth_m) in sites {
        let temperature: Vec<f64> = depth_m
            .iter()
            .map(|&d| temperature_c(d, surface_temperature_c, thermocline_depth_m))
            .collect();
        let mut ax = fig.axes(0, col);
        ax.plot(&temperature, &depth_m);
        ax.title(name)
            .xlabel(r"$T$ ($^\circ$C)")
            .ylim(0.0, 200.0)
            .grid(true);
        if col == 0 {
            ax.ylabel("Depth $d$ (m)");
        }
    }
    fig.link_all_y().expect("every site shares the same depth axis");
    fig
}