Horizontal Box Plot — Altair

A horizontal box plot displays the distribution of numerical data through quartiles with the boxes oriented horizontally. This orientation is particularly useful when category labels are long or when comparing many groups, as it allows for easier reading of labels on the y-axis.

Horizontal Box Plot rendered with Altair

Python source (Altair)

""" anyplot.ai
box-horizontal: Horizontal Box Plot
Library: altair 6.1.0 | Python 3.13.13
Quality: 86/100 | Updated: 2026-05-12
"""

import os

import altair as alt
import numpy as np
import pandas as pd


# Theme tokens
THEME = os.getenv("ANYPLOT_THEME", "light")
PAGE_BG = "#FAF8F1" if THEME == "light" else "#1A1A17"
ELEVATED_BG = "#FFFDF6" if THEME == "light" else "#242420"
INK = "#1A1A17" if THEME == "light" else "#F0EFE8"
INK_SOFT = "#4A4A44" if THEME == "light" else "#B8B7B0"

BRAND = "#009E73"  # Okabe-Ito position 1

# Data - Response times by service type
np.random.seed(42)

data = []
# Create distributions with different characteristics
distributions = {
    "Database Query": (120, 40, 5),  # mean, std, n_outliers
    "API Gateway": (85, 25, 3),
    "Authentication": (45, 15, 2),
    "File Storage": (200, 60, 4),
    "Cache Lookup": (15, 8, 2),
    "Email Service": (150, 50, 3),
}

for service, (mean, std, n_outliers) in distributions.items():
    # Main distribution
    values = np.random.normal(mean, std, 50)
    values = np.clip(values, 5, None)  # No negative response times
    # Add some outliers
    outliers = np.random.uniform(mean + 3 * std, mean + 5 * std, n_outliers)
    all_values = np.concatenate([values, outliers])
    for v in all_values:
        data.append({"Service": service, "Response Time (ms)": v})

df = pd.DataFrame(data)

# Sort by median for easier comparison
medians = df.groupby("Service")["Response Time (ms)"].median().sort_values()
df["Service"] = pd.Categorical(df["Service"], categories=medians.index, ordered=True)

# Create horizontal box plot
chart = (
    alt.Chart(df)
    .mark_boxplot(
        box=alt.MarkConfig(color=BRAND),
        median=alt.MarkConfig(color=INK, size=3),
        outliers=alt.MarkConfig(color=BRAND, size=80),
        ticks=alt.MarkConfig(color=BRAND),
        rule=alt.MarkConfig(color=BRAND),
    )
    .encode(
        x=alt.X("Response Time (ms):Q", title="Response Time (ms)", scale=alt.Scale(zero=False)),
        y=alt.Y("Service:N", title="Service Type", sort=list(medians.index)),
        tooltip=["Service:N", "Response Time (ms):Q"],
    )
    .properties(
        width=1600,
        height=900,
        background=PAGE_BG,
        title=alt.Title("box-horizontal · altair · anyplot.ai", fontSize=28, anchor="middle"),
    )
    .configure_axis(
        domainColor=INK_SOFT,
        tickColor=INK_SOFT,
        gridColor=INK,
        gridOpacity=0.12,
        labelColor=INK_SOFT,
        labelFontSize=18,
        titleColor=INK,
        titleFontSize=22,
        labelLimit=300,
    )
    .configure_title(color=INK)
    .configure_view(strokeWidth=0, fill=PAGE_BG)
    .interactive()
)

chart.save(f"plot-{THEME}.png", scale_factor=3.0)
chart.save(f"plot-{THEME}.html")

Part of Horizontal Box Plot on anyplot.ai.

Other implementations