Summer peaks , July leads at 74, February trails at 27 Figure 48.1 , Summer peaks , July leads at 74, February trails at 27

A Nightingale Rose (Coxcomb, Polar Area Diagram) is a radial bar chart where segments occupy equal angular slices and values are encoded as petal radius . Each ring from the centre represents a scale increment. The chart is drawn on a polar coordinate grid, which means values that are numerically similar appear in a circular spatial arrangement , useful when the data is genuinely cyclic (months in a year, hours in a day).

This chart has a known and serious flaw : petal area grows as r² , not r . A petal with value 74 has nearly seven times the area of a petal with value 27, even though the values differ by less than 3times. The area-correct toggle on slide 1 applies a square-root radius scale, which makes area proportional to value , correcting the distortion. Compare them. The corrected version is more honest. Nightingale almost certainly knew this.

Use a Nightingale Rose when the data is genuinely cyclic (months, quarters, compass bearings, hours) and the circular metaphor adds interpretive meaning that a bar chart cannot. Do not use it when your goal is precise comparison , the area distortion makes accurate reading nearly impossible without the values printed inside. Never use it for non-cyclic data: the circular arrangement implies a loop that doesn't exist.

The one decision worth knowing: petals animate clockwise from January at 12 o'clock , not from the highest value, and not alphabetically. Cyclic data has a natural reading order (the calendar), and preserving that order is more important than dramatic reveal. Starting at 12 o'clock mirrors how we read clocks and compasses, making the monthly pattern immediately legible without a legend.

FT Visual Vocabulary + Abela FT Visual Vocabulary: Part-to-whole / Cyclic Comparison . Abela quadrant: Comparison , comparing values across categories arranged in a cycle. Tufte would flag this chart's area distortion as a data-ink violation: non-data ink (the exaggerated outer area) is actively misleading, not merely decorative.

Paste this into Claude Code to generate a working version of this chart, plus its data file. The result will not be a perfect replica , the goal is that the reader can run the prompt, get a chart of this type, and read its source. Generate a complete, self-contained nightingale in D3 v7. Two files:

The ideas in this chapter didn't appear from nowhere. Florence Nightingale designed the polar-area "rose" diagram (now called the Nightingale chart) in 1858 to show that British soldiers in the Crimean War were dying overwhelmingly from preventable disease , not battle wounds. Her chart persuaded Parliament to reform military hygiene. Florence Nightingale, circa 1858. AI-generated portrait based on a public domain photograph (Wikimedia Commons).

The ideas in this chapter didn't appear from nowhere. Florence Nightingale designed the polar-area "rose" diagram (now called the Nightingale chart) in 1858 to show that British soldiers in the Crimean War were dying overwhelmingly from preventable disease , not battle wounds. Her chart persuaded Parliament to reform military hygiene. Florence Nightingale, circa 1858. AI-generated portrait based on a public domain photograph (Wikimedia Commons).