Pie Chart Maker

Pie Charts

A pie chart is a circular statistical graphic that is divided into slices to illustrate numerical proportion. In a pie chart, the arc length of each slice (and consequently its central angle and area), is proportional to the quantity it represents. While pie charts can be used to visualize some kinds of data, they also have limitations and there are often better alternatives.

When to Use a Pie Chart

Pie charts are most effective when trying to:

• Visualize the composition of something. For example, the market share held by different competitors in an industry. Each company would be represented by a slice of the pie proportional to their market share.

• Highlight individual segments or slices of a whole. Users can easily distinguish each slice, so a pie chart draws attention to how parts contribute to a whole.

• Compare parts of a whole. The slice sizes quickly communicate what percent each component represents.

• Display a small number of categories (usually less than 6). The slices become hard to distinguish with more categories.

Limitations of Pie Charts

Some key limitations of pie charts include:

• Difficulty comparing slices if the chart contains too many categories (greater than 5 or 6). Differences in slice size become less pronounced.

• Inability to show small slices effectively. Very thin slices are hard to label or distinguish.

• Difficult to visualize change over time. It's not possible to easily show how the components trend up or down.

• Pie charts are not area proportional, so they can distort data if not scaled properly. The same data plotted as a bar chart could look quite different.

• Only able to show a single data series. It's not possible to visualize a second data dimension.

Alternatives to Pie Charts

Some better alternatives for visualizing data include:

• Bar charts: Allow comparison of different values across categories through the length of the bars. Can show changes over time.

• Column charts: Useful for time series data or comparing several items. Height encodes values.

• Line charts: Ideal for visualizing trends over time. Lines connect successive data points.

• Donut charts: Similar to a pie chart but contains a blank center, allowing a label or additional information to be placed there.

The key is to use the right visual to communicate the relationships in your data. Pie charts work well for composition data but have limits. Consider alternate chart types if you need to convey trends, precise values, small differences, or multiple data series.