[heatmap-polar] Polar Heatmap for Cyclic Two-Dimensional Data

[MarkusNeusinger]

Description

A heatmap wrapped around a circle, where one axis (angular) represents a cyclic variable (e.g., hour of day, month) and the other axis (radial) represents a second categorical or ordinal variable (e.g., day of week). Cell color encodes the measured value. This is ideal for revealing patterns in data with inherent cyclical structure that rectangular heatmaps distort.

Applications

• Showing website traffic by hour of day × day of week
• Visualizing crime frequency by time and location zone
• Displaying energy consumption patterns by month × year
• Analyzing sensor data with daily/weekly cycles

Data

• angular (categorical/ordinal) — cyclic dimension (e.g., hours 0–23)
• radial (categorical/ordinal) — second dimension (e.g., Mon–Sun)
• value (float) — measured quantity
• Size: 7–52 radial × 12–24 angular bins typical

Notes

• Angular axis wraps around (0° and 360° are adjacent)
• Radial axis extends outward from center
• Sequential or diverging colormap
• Label angular positions (e.g., 12am, 6am, 12pm, 6pm)

[claude]

✅ Spec ID: heatmap-polar

Rationale: Combines the heatmap type with the polar coordinate variant — a color-encoded grid wrapped around a circle with angular and radial axes, distinct from all existing rectangular heatmaps and existing polar chart types (bar, line, scatter).

No duplicates or near-duplicates found among the 13 existing heatmap specs or 4 existing polar specs.

[github-actions]

✅ Specification Ready: heatmap-polar

PR: #5260

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specification.md

heatmap-polar: Polar Heatmap for Cyclic Two-Dimensional Data

Description

A heatmap wrapped around a circle where the angular axis represents a cyclic variable (e.g., hour of day, month) and the radial axis represents a second categorical or ordinal variable (e.g., day of week, year). Cell color encodes the measured value. This visualization reveals patterns in data with inherent cyclical structure that rectangular heatmaps distort, since the first and last angular bins are visually adjacent rather than separated at opposite ends of a row.

Applications

• Showing website traffic intensity by hour of day (angular) and day of week (radial)
• Visualizing crime frequency by time of day and location zone
• Displaying energy consumption patterns by month (angular) and year (radial)
• Analyzing sensor data with daily or weekly cycles across multiple stations or categories

Data

• angular (categorical/ordinal) - Cyclic dimension mapped to angular position (e.g., hours 0–23, months Jan–Dec)
• radial (categorical/ordinal) - Second dimension mapped to concentric rings outward from center (e.g., Mon–Sun, years)
• value (float) - Measured quantity encoded as cell color
• Size: 7–52 radial bins × 12–24 angular bins typical
• Example: Hourly website visits for each day of the week (7 radial × 24 angular = 168 cells)

Notes

• Angular axis wraps continuously — 0° and 360° are adjacent, preserving cyclic continuity
• Radial axis extends outward from center; innermost ring is the first radial category
• Use a sequential colormap for single-sign data or a diverging colormap when data has a meaningful midpoint
• Label angular positions at readable intervals (e.g., 12am, 6am, 12pm, 6pm for hourly data)
• Include a colorbar legend for value interpretation
• Consider adding thin gridlines or borders between cells for readability
• Outer rings have larger area than inner rings; interpret color (not area) as the encoded channel

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Next: Add approved label to merge this specification to main.

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🤖 spec-create workflow

[github-actions]

🚀 Specification Merged!

Specification: heatmap-polar
PR: #5260 (merged)

The specification is now in main and synced to PostgreSQL.

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Next: Add generate:{library} labels to start generating implementations.

Available libraries: matplotlib, seaborn, plotly, bokeh, altair, plotnine, pygal, highcharts, letsplot

Or use workflow dispatch for bulk operations.

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🤖 spec-create workflow