Data visualization tools give businesses a simple way to present statistical information using charts and graphs rather than a series of numbers. The pie chart is one of the most common of these tools. Its name comes from its resemblance to a pie, as it has a circular shape and shows data in slices. Simple to create and understand, a pie chart works well when you need to present and measure simple data, but it may not suit complex needs as well as other visualization tools such as bar graphs.
Overview of Pie Charts
At its most basic, a pie chart is a two-dimensional circle divided into a few slices. The chart as a whole represents the sum of all its data; individual slices show each piece of data as a percentage of the whole. If you create a pie chart showing product line performance, for example, and you have two lines that each account for 50 percent of turnover, your pie chart will simply have two halves. If there were a 75/25 split, the bigger line would take up three quarters of the chart, leaving one quarter for the other. Effects such as three-dimensional charting, slice pivoting and dragging slices out of the circle adds emphasis to individual data sets and makes charts more visually appealing.
Advantages of a Pie Chart
A pie chart presents data as a simple and easy-to-understand picture. It can be an effective communication tool for even an uninformed audience, because it represents data visually as a fractional part of a whole. Readers or audiences see a data comparison at a glance, enabling them to make an immediate analysis or to understand information quickly. This type of data visualization chart removes the need for readers to examine or measure underlying numbers themselves. You can also manipulate pieces of data in the pie circle to emphasize points you want to make.
Disadvantages of a Pie Chart
A pie chart becomes less effective if it uses too many pieces of data. For example, a chart with four slices is easy to read; one with more than 10 becomes less so, especially if it contains many similarly sized slices. Adding data labels and numbers may not help here, as they themselves may become crowded and hard to read. This kind of chart only represents one data set -- you need a series to compare multiple sets. This may make it more difficult for readers to analyze and assimilate information quickly. Comparing data slices in a circle also has its problems, because the reader has to factor in angles and compare non-adjacent slices. Data manipulation within the chart's design may lead readers to draw inaccurate conclusions or to make decisions based on visual impact rather than data analysis.
Alternatives to a Pie Chart
Other charts and graphs may be a better option, especially if you are handling many pieces of data or want to make comparisons between data sets. Doughnut charts share the circular shape and overall functionality of pie charts but add the ability to display multiple data sets. You can also place data labels and totals in the doughnut's hole, making it easier to compare segments. Bar graphs represent data by length, allowing for quick comparison and measurement. They may be easier to read if you need to present many pieces of data at a time or want to compare different sets of data in a single chart.