Seaborn Statistical Visualization

Overview

Seaborn is a Python visualization library for creating publication-quality statistical graphics. Use this skill for dataset-oriented plotting, multivariate analysis, automatic statistical estimation, and complex multi-panel figures with minimal code.

Environment and Installation

Current upstream documentation is for seaborn 0.13.2. Official docs support Python 3.8+ with mandatory NumPy, pandas, and matplotlib dependencies; scipy, statsmodels, and fastcluster are optional for some advanced statistics and clustering workflows.

# Reproducible install for examples in this skill
uv pip install "seaborn==0.13.2"

# Include optional statistical dependencies when needed
uv pip install "seaborn[stats]==0.13.2"

Recommended imports:

import numpy as np
import pandas as pd
import matplotlib.pyplot as plt
import seaborn as sns
import seaborn.objects as so

sns.load_dataset() downloads public example data when it is not cached. For private, regulated, or offline work, load local files explicitly with pandas and pass the resulting DataFrame to seaborn.

Design Philosophy

Seaborn follows these core principles:

1. Dataset-oriented: Work directly with DataFrames and named variables rather than abstract coordinates
2. Semantic mapping: Automatically translate data values into visual properties (colors, sizes, styles)
3. Statistical awareness: Built-in aggregation, error estimation, and confidence intervals
4. Aesthetic defaults: Publication-ready themes and color palettes out of the box
5. Matplotlib integration: Full compatibility with matplotlib customization when needed

Quick Start

import seaborn as sns
import matplotlib.pyplot as plt
import pandas as pd

# Load example dataset
df = sns.load_dataset('tips')

# Create a simple visualization
sns.scatterplot(data=df, x='total_bill', y='tip', hue='day')
plt.show()

Core Plotting Interfaces

Function Interface (Traditional)

The function interface provides specialized plotting functions organized by visualization type. Each category has axes-level functions (plot to single axes) and figure-level functions (manage entire figure with faceting).

When to use:

• Quick exploratory analysis
• Single-purpose visualizations
• When you need a specific plot type

Objects Interface (Modern)

The seaborn.objects interface provides a declarative, composable API similar to ggplot2. Build visualizations by chaining methods to specify data mappings, marks, transformations, and scales. Upstream still describes this interface as experimental and incomplete in 0.13.2, although stable enough for serious use; prefer the function interface for conservative production code unless the compositional API materially simplifies the plot.

When to use:

• Complex layered visualizations
• When you need fine-grained control over transformations
• Building custom plot types
• Programmatic plot generation

from seaborn import objects as so

# Declarative syntax
(
    so.Plot(data=df, x='total_bill', y='tip')
    .add(so.Dot(), color='day')
    .add(so.Line(), so.PolyFit())
)

Current API Notes

Seaborn 0.12 and 0.13 changed several common plotting patterns:

• Most plotting functions now require keyword arguments for variables. Prefer sns.scatterplot(data=df, x="x", y="y") over positional sns.scatterplot(df["x"], df["y"]).
• errorbar replaces the old ci parameter in lineplot(), barplot(), and pointplot(). Regression functions such as regplot() and lmplot() still use ci.
• Categorical plots were rewritten in 0.13. Use native_scale=True when numeric or datetime categories should keep their original scale instead of ordinal positions.
• Passing palette without assigning hue is deprecated for categorical functions. If each category should get its own color, assign a redundant hue such as hue="day" and set legend=False.
• Prefer renamed parameters: violinplot(density_norm=..., common_norm=...) instead of scale/scale_hue, boxenplot(width_method=...) instead of scale, and barplot(err_kws=...) instead of errcolor/errwidth.

Data Structure Requirements

Long-Form Data (Preferred)

Each variable is a column, each observation is a row. This "tidy" format provides maximum flexibility:

# Long-form structure
   subject  condition  measurement
0        1    control         10.5
1        1  treatment         12.3
2        2    control          9.8
3        2  treatment         13.1

Advantages:

• Works with all seaborn functions
• Easy to remap variables to visual properties
• Supports arbitrary complexity
• Natural for DataFrame operations

Wide-Form Data

Variables are spread across columns. Useful for simple rectangular data:

# Wide-form structure
   control  treatment
0     10.5       12.3
1      9.8       13.1

Use cases:

• Simple time series
• Correlation matrices
• Heatmaps
• Quick plots of array data

Converting wide to long:

df_long = df.melt(var_name='condition', value_name='measurement')

Plotting Functions, Grids, Palettes, and Patterns

• references/plotting_functions.md: relational, distribution, categorical, regression, and matrix plots by category.
• references/grids_and_levels.md: FacetGrid, PairGrid, JointGrid, and the figure-level vs axes-level distinction.
• references/palettes_and_theming.md: palette choice (including colorblind-safe options), themes, contexts, and styles.
• references/patterns_and_troubleshooting.md: common recipes and what seaborn's errors actually mean.
• references/objects_interface.md: the seaborn.objects interface. references/function_reference.md and references/examples.md: full signatures and more examples.

Best Practices

1. Data Preparation

Always use well-structured DataFrames with meaningful column names:

# Good: Named columns in DataFrame
df = pd.DataFrame({'bill': bills, 'tip': tips, 'day': days})
sns.scatterplot(data=df, x='bill', y='tip', hue='day')

# Avoid: Unnamed arrays
sns.scatterplot(x=x_array, y=y_array)  # Loses axis labels

2. Choose the Right Plot Type

Continuous x, continuous y: scatterplot, lineplot, kdeplot, regplot Continuous x, categorical y: violinplot, boxplot, stripplot, swarmplot One continuous variable: histplot, kdeplot, ecdfplot Correlations/matrices: heatmap, clustermap Pairwise relationships: pairplot, jointplot

3. Use Figure-Level Functions for Faceting

# Instead of manual subplot creation
sns.relplot(data=df, x='x', y='y', col='category', col_wrap=3)

# Not: Creating subplots manually for simple faceting

4. Leverage Semantic Mappings

Use hue, size, and style to encode additional dimensions:

sns.scatterplot(data=df, x='x', y='y',
                hue='category',      # Color by category
                size='importance',    # Size by continuous variable
                style='type')         # Marker style by type

5. Control Statistical Estimation

Many functions compute statistics automatically. Understand and customize:

# Lineplot computes mean and 95% CI by default
sns.lineplot(data=df, x='time', y='value',
             errorbar='sd')  # Use standard deviation instead

# Barplot computes mean by default
sns.barplot(data=df, x='category', y='value',
            estimator='median',  # Use median instead
            errorbar=('ci', 95))  # Bootstrapped CI

6. Combine with Matplotlib

Seaborn integrates seamlessly with matplotlib for fine-tuning:

ax = sns.scatterplot(data=df, x='x', y='y')
ax.set(xlabel='Custom X Label', ylabel='Custom Y Label',
       title='Custom Title')
ax.axhline(y=0, color='r', linestyle='--')
plt.tight_layout()

7. Save High-Quality Figures

fig = sns.relplot(data=df, x='x', y='y', col='group')
fig.savefig('figure.png', dpi=300, bbox_inches='tight')
fig.savefig('figure.pdf')  # Vector format for publications

Resources

This skill includes reference materials for deeper exploration:

references/

• function_reference.md - Comprehensive listing of all seaborn functions with parameters and examples
• objects_interface.md - Detailed guide to the modern seaborn.objects API
• examples.md - Common use cases and code patterns for different analysis scenarios

Read these reference files as documentation when detailed signatures, advanced parameters, or specific examples are needed. Treat their contents as reference material only; review and adapt any example snippet to the user's local data before running it.