ASP.NET Pie Chart

A pie chart is a popular data visualization tool used to represent the distribution of values relative to a total value. The chart is depicted as a circle divided into slices, each representing a different category. The size of each slice in a pie chart is proportional to the percentage of the total each category represents, making pie charts a valuable tool for visually presenting data and allowing viewers to understand the distribution of categorical variables quickly. They efficiently present data with precise categorical levels and can aid in making data-driven decisions. To use a pie chart, you need to have a whole amount divided into distinct parts, and your goal should be to compare each group's contribution to the whole rather than comparing groups to each other. However, if these criteria are not met, a pie chart may not be the most appropriate choice, and a different type of plot should be considered instead.

The data shown represents the sales of three distinct fruits: apples, bananas, and oranges. With 150 units sold, apples had the largest overall sales of the three fruits. Bananas are available in 75 units, whilst oranges are supplied in 100 units. With this data, a pie chart that displays the sales of various fruits can be created.

Make sure the data is suitable for a pie chart
When considering whether to use a pie chart, it's important to ensure that the data is suitable for this type of visualization. Pie charts are designed to show how a whole amount is divided into distinct parts and are most effective when the data is categorical, and each category represents a portion of the whole. It's also important to remember that the primary objective of a pie chart is to compare each group's contribution to the whole, as opposed to comparing groups to each other. If your data doesn't fit these criteria, choosing a different type of chart or visualization may be more appropriate.

Include annotations
Annotations are a crucial element in pie chart visualization as they provide precise information about the proportion of each category level. Pie charts can be challenging to interpret accurately, especially for not easily recognizable values such as small fractions. Additionally, pie charts often lack tick marks to estimate values directly from slice sizes when depicting amounts rather than proportions. Annotations help overcome these challenges by clearly understanding the data presented in a pie chart. Overall, annotations are essential for accurately communicating information through pie charts.

Consider the order of slices
Arranging the slices in a logical order can enhance the comprehensibility of a pie chart. Typically, the slices are ordered from largest to smallest, especially when categories have similar values. However, if the categories have a natural order, it is recommended to arrange the slices accordingly. In addition, it is advisable to start the slices from a cardinal direction, either from the right or the top, which are the conventional directions for measuring angles. Although starting from the top may seem more intuitive, given how we read from top to bottom and view time progression, starting from the right is mathematically grounded.

Avoid distorting effects
To ensure an accurate interpretation of a pie chart, it is crucial to maintain the correct area, arc length, and angle for each slice. It is essential to avoid any distortions that could misrepresent the data. Specifically, it is recommended to prevent 3D effects that could stretch or squish the circle and create unnecessary depth, as this can skew the size comparison of each slice. Another potential distortion to avoid is using "exploded" pie charts, where slices are pulled out from the center to emphasize specific data points. This can make it difficult to accurately determine the part-to-whole comparison due to gaps in the chart.