The major flaw with Nightingale Rose Charts is that the outer segments are given more emphasis because of their larger area size. This disproportionately represents increases in value.
This chart was famously used by statistician and medical reformer, Florence Nightingale to communicate the avoidable deaths of soldiers during the Crimean war.
Nightingale Rose Charts are drawn on a polar coordinate grid. Each category or interval in the data is divided into equal segments on this radial chart. How far each segment extends from the centre of the polar axis depends on the value it represents. So each ring from the centre of the polar grid can be used as a scale to plot the segment size and represent a higher value. Therefore, it’s important to notice with Nightingale Rose Charts that it’s the area, rather than the radius of a segment that represents its value.
Also known as a Coxcomb Chart, Polar Area Diagram.