A pie chart is a graphical representation of statistical data in the form of a circle. The circle is typically divided into segments, determined by arc length, that extend to its center. Its segments resemble slices of a pie, however, there are other types of pie charts (or hybrids) which represent segments in different ways.
Pie charts are used to represent statistical information like population demographics or market demographics. Their standard form offers information that is limited both in scope and depth. Many experts believe that they should be totally avoided, however, there are many types of pie charts that have various applications, and that are the most appropriate type of graphical representation for that data type. A selection of pie charts is presented below:
- Exploded Pie Chart: These are charts which separate one or more segments from the body of the chart. This is an effect designed to draw attention to a particular metric.
Multilevel Pie Chart: These are charts that utilize concentric circles (or rings) to represent data. There is a hierarchical relationship between the rings and the inner circle. The rings are also sometimes further divided into slice segments to represent data.
Doughnut Chart: These are simplified versions of multilevel charts. They utilize one concentric ring and a center circle to represent data.
These options offer a deeper and wider level of expression, but pie charts still suffer from other limitations. When compared with bar charts, it is much harder to accurately and clearly represent certain differences in data. When a pie chart divided into segments with minor differences is viewed, those differences are less distinct than a typical bar chart. These graphics are designed to concentrate and clarify large datasets, and examine their relationships. Issues with basic clarity are the antithesis of that, so it is easy to see why some believe they should never be used.