Ympyräkaaviot

Ympyräkaaviot, also known as pie charts, are a type of graphical representation of data. They are circular statistical graphics that are divided into slices to illustrate numerical proportion. In a pie chart, the arc length of each slice, as well as its central angle and area, are proportional to the quantity it represents. For example, if the data is in percentages, a slice representing 25% of the total would take up a quarter of the circle's area.

Pie charts are commonly used to show how a whole is divided into parts. They are effective for displaying simple comparisons of proportions within a dataset. However, they become less effective when dealing with a large number of categories or when the proportions are very similar, making it difficult to distinguish between the slices. It is generally recommended to use pie charts when there are only a few categories, typically no more than five or six.

The origin of the pie chart is often attributed to William Playfair, who introduced it in his "Statistical Breviary" in 1801. Since then, pie charts have become a ubiquitous tool in business, statistics, and everyday data visualization. Despite their widespread use, there are ongoing discussions among data visualization experts about the optimal use cases for pie charts, with some advocating for alternatives like bar charts for better clarity in certain situations.