seaborn

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.

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

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.

When to use:

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

Plotting Functions by Category

Relational Plots (Relationships Between Variables)

Use for: Exploring how two or more variables relate to each other

• scatterplot() - Display individual observations as points
• lineplot() - Show trends and changes (automatically aggregates and computes CI)
• relplot() - Figure-level interface with automatic faceting

Key parameters:

• x, y - Primary variables
• hue - Color encoding for additional categorical/continuous variable
• size - Point/line size encoding
• style - Marker/line style encoding
• col, row - Facet into multiple subplots (figure-level only)

Distribution Plots (Single and Bivariate Distributions)

Use for: Understanding data spread, shape, and probability density

• histplot() - Bar-based frequency distributions with flexible binning
• kdeplot() - Smooth density estimates using Gaussian kernels
• ecdfplot() - Empirical cumulative distribution (no parameters to tune)
• rugplot() - Individual observation tick marks
• displot() - Figure-level interface for univariate and bivariate distributions
• jointplot() - Bivariate plot with marginal distributions
• pairplot() - Matrix of pairwise relationships across dataset

Key parameters:

• x, y - Variables (y optional for univariate)
• hue - Separate distributions by category
• stat - Normalization: "count", "frequency", "probability", "density"
• bins / binwidth - Histogram binning control
• bw_adjust - KDE bandwidth multiplier (higher = smoother)
• fill - Fill area under curve
• multiple - How to handle hue: "layer", "stack", "dodge", "fill"

Categorical Plots (Comparisons Across Categories)

Use for: Comparing distributions or statistics across discrete categories

Categorical scatterplots:

• stripplot() - Points with jitter to show all observations
• swarmplot() - Non-overlapping points (beeswarm algorithm)

Distribution comparisons:

• boxplot() - Quartiles and outliers
• violinplot() - KDE + quartile information
• boxenplot() - Enhanced boxplot for larger datasets

Statistical estimates:

• barplot() - Mean/aggregate with confidence intervals
• pointplot() - Point estimates with connecting lines
• countplot() - Count of observations per category

Figure-level:

• catplot() - Faceted categorical plots (set kind parameter)

Key parameters:

• x, y - Variables (one typically categorical)
• hue - Additional categorical grouping
• order, hue_order - Control category ordering
• dodge - Separate hue levels side-by-side
• orient - "v" (vertical) or "h" (horizontal)
• kind - Plot type for catplot: "strip", "swarm", "box", "violin", "bar", "point"

Regression Plots (Linear Relationships)

Use for: Visualizing linear regressions and residuals

• regplot() - Axes-level regression plot with scatter + fit line
• lmplot() - Figure-level with faceting support
• residplot() - Residual plot for assessing model fit

Key parameters:

• x, y - Variables to regress
• order - Polynomial regression order
• logistic - Fit logistic regression
• robust - Use robust regression (less sensitive to outliers)
• ci - Confidence interval width (default 95)
• scatter_kws, line_kws - Customize scatter and line properties

Matrix Plots (Rectangular Data)

Use for: Visualizing matrices, correlations, and grid-structured data

• heatmap() - Color-encoded matrix with annotations
• clustermap() - Hierarchically-clustered heatmap

Key parameters:

• data - 2D rectangular dataset (DataFrame or array)
• annot - Display values in cells
• fmt - Format string for annotations (e.g., ".2f")
• cmap - Colormap name
• center - Value at colormap center (for diverging colormaps)
• vmin, vmax - Color scale limits
• square - Force square cells
• linewidths - Gap between cells

Multi-Plot Grids

Seaborn provides grid objects for creating complex multi-panel figures:

FacetGrid

Create subplots based on categorical variables. Most useful when called through figure-level functions (relplot, displot, catplot), but can be used directly for custom plots.

PairGrid

Show pairwise relationships between all variables in a dataset.

JointGrid

Combine bivariate plot with marginal distributions.

Figure-Level vs Axes-Level Functions

Understanding this distinction is crucial for effective seaborn usage:

Axes-Level Functions

• Plot to a single matplotlib Axes object
• Integrate easily into complex matplotlib figures
• Accept ax= parameter for precise placement
• Return Axes object
• Examples: scatterplot, histplot, boxplot, regplot, heatmap

When to use:

• Building custom multi-plot layouts
• Combining different plot types
• Need matplotlib-level control
• Integrating with existing matplotlib code

Figure-Level Functions

• Manage entire figure including all subplots
• Built-in faceting via col and row parameters
• Return FacetGrid, JointGrid, or PairGrid objects
• Use height and aspect for sizing (per subplot)
• Cannot be placed in existing figure
• Examples: relplot, displot, catplot, lmplot, jointplot, pairplot

When to use:

• Faceted visualizations (small multiples)
• Quick exploratory analysis
• Consistent multi-panel layouts
• Don't need to combine with other plot types

Data Structure Requirements

Long-Form Data (Preferred)

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

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:

Use cases:

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

Converting wide to long:

Color Palettes

Seaborn provides carefully designed color palettes for different data types:

Qualitative Palettes (Categorical Data)

Distinguish categories through hue variation:

• "deep" - Default, vivid colors
• "muted" - Softer, less saturated
• "pastel" - Light, desaturated
• "bright" - Highly saturated
• "dark" - Dark values
• "colorblind" - Safe for color vision deficiency

Sequential Palettes (Ordered Data)

Show progression from low to high values:

• "rocket", "mako" - Wide luminance range (good for heatmaps)
• "flare", "crest" - Restricted luminance (good for points/lines)
• "viridis", "magma", "plasma" - Matplotlib perceptually uniform

Diverging Palettes (Centered Data)

Emphasize deviations from a midpoint:

• "vlag" - Blue to red
• "icefire" - Blue to orange
• "coolwarm" - Cool to warm
• "Spectral" - Rainbow diverging

Custom Palettes

Theming and Aesthetics

Set Theme

set_theme() controls overall appearance:

Styles

Control background and grid appearance:

• "darkgrid" - Gray background with white grid (default)
• "whitegrid" - White background with gray grid
• "dark" - Gray background, no grid
• "white" - White background, no grid
• "ticks" - White background with axis ticks

Contexts

Scale elements for different use cases:

• "paper" - Smallest (default)
• "notebook" - Slightly larger
• "talk" - Presentation slides
• "poster" - Large format

Best Practices

1. Data Preparation

Always use well-structured DataFrames with meaningful column names:

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

4. Leverage Semantic Mappings

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

5. Control Statistical Estimation

Many functions compute statistics automatically. Understand and customize:

6. Combine with Matplotlib

Seaborn integrates seamlessly with matplotlib for fine-tuning:

7. Save High-Quality Figures

Common Patterns

Exploratory Data Analysis

Publication-Quality Figures

Complex Multi-Panel Figures

Time Series with Confidence Bands

Troubleshooting

Issue: Legend Outside Plot Area

Figure-level functions place legends outside by default. To move inside:

Issue: Overlapping Labels

Issue: Figure Too Small

For figure-level functions:

For axes-level functions:

Issue: Colors Not Distinct Enough

Issue: KDE Too Smooth or Jagged

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

Load reference files as needed for detailed function signatures, advanced parameters, or specific examples.