Scientific figures one dataset, three palettes, the code and the licences

"""Three publication figures from one dataset, in color-blind-safe palettes.

From https://auricartisan.com/library/palette/scientific/ - CC0 1.0.

The data is computed, not measured: the hours from sunrise to sunset at the
centre of the sun, without refraction, from Cooper's (1969) solar declination.
So the figures can be rebuilt anywhere, and checked against the page.

    python figures.py          writes figure-1, figure-2 and figure-3
                               as .pdf, .svg and .png (600 dpi)
    python figures.py --grid   prints the 9 x 12 grid of hours as JSON

Needs matplotlib and NumPy.
"""
import json
import sys

import matplotlib
import numpy as np

matplotlib.use("Agg")
import matplotlib.pyplot as plt  # noqa: E402
from matplotlib.colors import BoundaryNorm, ListedColormap  # noqa: E402

# Okabe and Ito (2008), in the order that keeps the first n colors furthest
# apart in every color vision (see the chart palettes page). One marker each.
OKABE_ITO = ["#0072B2", "#D55E00", "#000000", "#CC79A7"]
MARKERS = ["o", "s", "^", "D"]
# viridis (van der Walt and Smith, CC0) and PuOr (ColorBrewer, Apache 2.0), nine stops each.
VIRIDIS = ["#440154", "#472D7B", "#3B528B", "#2C728E", "#21918C", "#28AE80", "#5EC962", "#ADDC30", "#FDE725"]
PUOR = ["#B35806", "#E08214", "#FDB863", "#FEE0B6", "#F7F7F7", "#D8DAEB", "#B2ABD2", "#8073AC", "#542788"]

LATITUDES = [60, 45, 30, 15, 0, -15, -30, -45, -60]
MONTHS = ["Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"]
DAYS = [15, 46, 74, 105, 135, 166, 196, 227, 258, 288, 319, 349]  # the 15th of each month
# Nine classes of 1.5 hours, centred on 12: the middle class is days about as long as nights.
EDGES = 12 + 1.5 * (np.arange(10) - 4.5)

INK = "#000000"
PAPER = "#FFFFFF"


def declination(day):
    """Solar declination in degrees: Cooper (1969)."""
    return 23.45 * np.sin(np.radians(360 * (284 + day) / 365))


def day_length(lat, day):
    """N = (2/15) arccos(-tan(latitude) tan(declination)), in hours."""
    x = -np.tan(np.radians(lat)) * np.tan(np.radians(declination(day)))
    return np.where(x <= -1, 24.0, np.where(x >= 1, 0.0, 2 * np.degrees(np.arccos(np.clip(x, -1, 1))) / 15))


def grid():
    return np.array([[float(day_length(lat, d)) for d in DAYS] for lat in LATITUDES])


def lat_label(lat):
    return "0°" if lat == 0 else f"{abs(lat)}°{'N' if lat > 0 else 'S'}"


def luminance(hex_color):
    c = np.array([int(hex_color[i:i + 2], 16) for i in (1, 3, 5)]) / 255
    c = np.where(c <= 0.04045, c / 12.92, ((c + 0.055) / 1.055) ** 2.4)
    return float(0.2126 * c[0] + 0.7152 * c[1] + 0.0722 * c[2])


def ink_on(hex_color):
    """Black or white, whichever has the higher WCAG contrast on the cell."""
    y = luminance(hex_color)
    return INK if (y + 0.05) / 0.05 >= 1.05 / (y + 0.05) else PAPER


def style():
    plt.rcParams.update({
        "font.family": "DejaVu Sans",
        "font.size": 7,
        "axes.spines.top": False,
        "axes.spines.right": False,
        "axes.linewidth": 0.6,
        "xtick.major.width": 0.6,
        "ytick.major.width": 0.6,
        "pdf.fonttype": 42,          # embed TrueType, as journals ask
        "svg.fonttype": "path",      # draw the SVG's text as outlines: it looks the same anywhere
        "svg.hashsalt": "auric-artisan",
    })


def figure_lines():
    """Categorical: day length through the year at four latitudes, labelled at the line ends."""
    fig, ax = plt.subplots(figsize=(3.5, 2.4), layout="constrained")
    days = np.arange(1, 366)
    for lat, color, marker in zip([60, 45, 30, 0], OKABE_ITO, MARKERS):
        hours = day_length(lat, days)
        ax.plot(days, hours, color=color, lw=1.4, marker=marker, markevery=(14, 30), ms=3.6,
                markeredgecolor=PAPER, markeredgewidth=0.5)
        ax.text(371, hours[-1], lat_label(lat), va="center", ha="left", color=INK)
    ax.set_xlim(1, 400)
    ax.set_ylim(0, 24)
    ax.set_xticks([1, 91, 182, 274, 365])
    ax.set_yticks([0, 6, 12, 18, 24])
    ax.set_xlabel("Day of the year")
    ax.set_ylabel("Day length (hours)")
    return fig


def figure_grid(values, colors, edges, label, fmt):
    """A latitude-by-month grid in nine classes, every value printed in its cell."""
    fig, ax = plt.subplots(figsize=(7.2, 3.0), layout="constrained")
    cmap = ListedColormap(colors)
    norm = BoundaryNorm(edges, cmap.N)
    mesh = ax.pcolormesh(values, cmap=cmap, norm=norm, edgecolors=PAPER, linewidth=0.6)
    for i, row in enumerate(values):
        for j, v in enumerate(row):
            cell = colors[int(np.clip(np.searchsorted(edges, v, side="right") - 1, 0, len(colors) - 1))]
            ax.text(j + 0.5, i + 0.5, fmt(v), ha="center", va="center", fontsize=6.5, color=ink_on(cell))
    ax.set_xticks(np.arange(12) + 0.5, MONTHS)
    ax.set_yticks(np.arange(9) + 0.5, [lat_label(lat) for lat in LATITUDES])
    ax.invert_yaxis()
    ax.tick_params(length=0)
    for side in ("left", "bottom"):
        ax.spines[side].set_visible(False)
    bar = fig.colorbar(mesh, ax=ax, ticks=edges, fraction=0.04, pad=0.02)
    bar.ax.set_yticklabels([f"{e:g}" for e in edges])
    bar.set_label(label)
    bar.outline.set_linewidth(0.6)
    return fig


def main():
    hours = grid()
    if "--grid" in sys.argv:
        print(json.dumps(hours.round(9).tolist()))
        return
    style()
    figures = {
        "figure-1": figure_lines(),
        "figure-2": figure_grid(hours, VIRIDIS, EDGES, "Day length (hours)", lambda v: f"{v:.1f}"),
        "figure-3": figure_grid(hours - 12, PUOR, EDGES - 12, "Difference from 12 hours (hours)", lambda v: f"{v:+.1f}"),
    }
    for name, fig in figures.items():
        fig.savefig(f"{name}.pdf", metadata={"CreationDate": None})
        fig.savefig(f"{name}.svg", metadata={"Date": None})
        fig.savefig(f"{name}.png", dpi=600)
        plt.close(fig)
        print(name)


if __name__ == "__main__":
    main()

pip install matplotlib numpy
python figures.py