Basic Polar Chart — Pygal

A polar chart displays data points on a circular coordinate system where position is determined by angle (theta) and distance from center (radius). This visualization is ideal for cyclical patterns, directional data, or any dataset where angular relationships are meaningful. It reveals periodic trends and directional distributions that would be obscured in Cartesian coordinates.

Basic Polar Chart rendered with Pygal

Python source (Pygal)

""" anyplot.ai
polar-basic: Basic Polar Chart
Library: pygal 3.1.3 | Python 3.13.14
Quality: 88/100 | Updated: 2026-07-24
"""

import importlib
import os
import sys

import numpy as np


# Remove script dir so 'pygal' resolves to the installed package, not this file
_d = os.path.abspath(os.path.dirname(__file__))
sys.path = [p for p in sys.path if os.path.abspath(p) != _d]
os.chdir(_d)

pygal = importlib.import_module("pygal")
Style = importlib.import_module("pygal.style").Style

# Theme tokens
THEME = os.getenv("ANYPLOT_THEME", "light")
PAGE_BG = "#FAF8F1" if THEME == "light" else "#1A1A17"
INK = "#1A1A17" if THEME == "light" else "#F0EFE8"
INK_MUTED = "#6B6A63" if THEME == "light" else "#A8A79F"

# Imprint palette — first series always brand green
IMPRINT_PALETTE = ("#009E73", "#C475FD", "#4467A3", "#BD8233", "#AE3030", "#2ABCCD", "#954477", "#99B314")

# Data — hourly temperature readings over a 24-hour cycle
np.random.seed(42)
hours = np.arange(24)
base_temp = 15 + 8 * np.sin((hours - 6) * np.pi / 12)  # peak at noon
temperature = base_temp + np.random.randn(24) * 1.5
peak_idx = int(np.argmax(temperature))

# Angular labels at standard cardinal intervals (00:00, 06:00, 12:00, 18:00),
# plus a callout on the peak hour to emphasize the diurnal cycle's high point
# — dense per-hour labels would crowd a circular axis, so every other point
# stays unlabeled.
cardinal_hours = {0, 6, 12, 18}


def _hour_label(h):
    if h == peak_idx:
        return f"{h:02d}:00 (peak)"
    if h in cardinal_hours:
        return f"{h:02d}:00"
    return ""


hour_labels = [_hour_label(h) for h in hours]

# Style — canonical pygal sizing for the 2400x2400 canvas (native-pixel family)
custom_style = Style(
    background=PAGE_BG,
    plot_background=PAGE_BG,
    foreground=INK,
    foreground_strong=INK,
    foreground_subtle=INK_MUTED,
    colors=IMPRINT_PALETTE,
    title_font_size=66,
    label_font_size=56,
    major_label_font_size=44,
    legend_font_size=44,
    value_font_size=36,
    stroke_width=4,
)

# Plot — radar chart for cyclical polar data
chart = pygal.Radar(
    style=custom_style,
    width=2400,
    height=2400,
    title="Hourly Temperature (°C) · polar-basic · python · pygal · anyplot.ai",
    show_legend=False,
    fill=True,
    dots_size=9,
    show_y_guides=True,
    inner_radius=0.1,
    margin_top=140,
)

chart.x_labels = hour_labels
chart.add("Temperature (°C)", [float(t) for t in temperature])

# Save
chart.render_to_png(f"plot-{THEME}.png")
with open(f"plot-{THEME}.html", "wb") as f:
    f.write(chart.render())

Part of Basic Polar Chart on anyplot.ai.

Other implementations