Stacked Area Chart with Confidence Bands — Pygal

A stacked area chart that displays multiple data series as cumulative areas, with each series surrounded by uncertainty or confidence bands. This visualization combines the composition insight of stacked areas with the statistical rigor of confidence intervals, making it ideal for showing how parts contribute to a whole while simultaneously communicating uncertainty in each component. The bands reveal where estimates are precise versus uncertain across the stacked series.

Stacked Area Chart with Confidence Bands rendered with Pygal

Python source (Pygal)

""" anyplot.ai
area-stacked-confidence: Stacked Area Chart with Confidence Bands
Library: pygal 3.1.0 | Python 3.13.13
Quality: 87/100 | Updated: 2026-05-18
"""

import os
import sys

import numpy as np


sys.path = [p for p in sys.path if p != ""]

import pygal
from pygal.style import Style


THEME = os.getenv("ANYPLOT_THEME", "light")
PAGE_BG = "#FAF8F1" if THEME == "light" else "#1A1A17"
INK = "#1A1A17" if THEME == "light" else "#F0EFE8"
INK_SOFT = "#4A4A44" if THEME == "light" else "#B8B7B0"

if THEME == "light":
    band_color_a = "#A0E0BB"
    center_color_a = "#009E73"
    band_color_b = "#F0C68A"
    center_color_b = "#C475FD"
    band_color_c = "#7FC4E8"
    center_color_c = "#4467A3"
else:
    band_color_a = "#1FA862"
    center_color_a = "#009E73"
    band_color_b = "#C64500"
    center_color_b = "#C475FD"
    band_color_c = "#0058A3"
    center_color_c = "#4467A3"

np.random.seed(42)
quarters = ["Q1'24", "Q2'24", "Q3'24", "Q4'24", "Q1'25", "Q2'25", "Q3'25", "Q4'25"]

product_a = np.array([120.0, 125.0, 130.0, 140.0, 145.0, 150.0, 158.0, 165.0])
uncertainty_a = np.array([8.0, 9.0, 8.5, 10.0, 9.5, 11.0, 10.5, 12.0])
a_lower = (product_a - uncertainty_a).tolist()
a_upper = (product_a + uncertainty_a).tolist()
a_center = product_a.tolist()

product_b = np.array([80.0, 85.0, 88.0, 92.0, 95.0, 100.0, 105.0, 110.0])
uncertainty_b = np.array([6.0, 7.0, 7.5, 8.0, 8.5, 9.0, 9.5, 10.0])
b_lower = (product_b - uncertainty_b).tolist()
b_upper = (product_b + uncertainty_b).tolist()
b_center = product_b.tolist()

product_c = np.array([30.0, 40.0, 55.0, 70.0, 85.0, 95.0, 105.0, 115.0])
uncertainty_c = np.array([12.0, 15.0, 18.0, 20.0, 22.0, 24.0, 25.0, 26.0])
c_lower = (product_c - uncertainty_c).tolist()
c_upper = (product_c + uncertainty_c).tolist()
c_center = product_c.tolist()

custom_style = Style(
    background=PAGE_BG,
    plot_background=PAGE_BG,
    foreground=INK,
    foreground_strong=INK,
    foreground_subtle=INK_SOFT,
    colors=(
        band_color_a,
        center_color_a,
        band_color_a,
        band_color_b,
        center_color_b,
        band_color_b,
        band_color_c,
        center_color_c,
        band_color_c,
    ),
    title_font_size=28,
    label_font_size=22,
    major_label_font_size=18,
    legend_font_size=16,
    value_font_size=14,
    stroke_width=2,
)

chart = pygal.StackedLine(
    width=4800,
    height=2700,
    style=custom_style,
    title="area-stacked-confidence · Python · pygal · anyplot.ai",
    x_title="Quarter",
    y_title="Revenue ($M)",
    fill=True,
    show_dots=False,
    show_x_guides=False,
    show_y_guides=True,
    legend_at_bottom=True,
    margin=80,
    spacing=40,
)

chart.x_labels = quarters

chart.add(None, a_lower)
chart.add("Product A (with 90% CI)", a_center)
chart.add(None, a_upper)

chart.add(None, b_lower)
chart.add("Product B (with 90% CI)", b_center)
chart.add(None, b_upper)

chart.add(None, c_lower)
chart.add("Product C (with 90% CI)", c_center)
chart.add(None, c_upper)

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

Part of Stacked Area Chart with Confidence Bands on anyplot.ai.

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