Pie chart

From Business Intelligence

Tufte-inspired pie chart. Whenever possible, don't use a pie chart. If you must use a pie chart, one designed like this is ideal. Start a very small data set with visible differences between values, and arrange the values in ascending order. Select colors with sufficiently high contrast that also have sufficiently different saturation values for color-blind people.

University degrees, diplomas and certificates granted. As far as pie charts go, this isn't bad. The data set is fairly small and it makes sense to add it to a whole. However, the values are fairly similar to each other which means that differences are difficult to see. Additionally, the human eye is not good at discerning differences in area size - for example, the Humanities slice doesn't look half the size of the Social and behavior slice, partly because area is hard to estimate and partly because the darker color lends it more weight.

Description

This common graph is a circle with pie-shaped "slices" on a polar plane. Each slice represents a quantitative proportion of the whole data set, usually expressed in percentages. To see the proportion of variables as parts of a whole. Pie charts are common and thus easily interpreted.

Considerations

• Pie charts should be avoided whenever possible because they do not convey exact values very well, and people find it difficult to visually evaluate circles in this way. Try using a bar chart, a table, or tree map instead.
• If you must use a pie chart, try arranging the slices largest to smallest, starting at 12:00 and moving clockwise.
• The difference in slice size must be obvious.
• Having many slices makes the data difficult to read and understand.
• Pie charts should never be used when the data items do not add up to a whole, or 100%.

Related techniques

Donut chart: Also known as a ring chart. Similar to the pie chart, except with several datasets. These are arranged in concentric rings sliced into portions. Each color represents the same variable in the dataset, with size showing the proportion. Donut charts should be avoided even more than pie charts. For most situations, the stacked column/bar chart is a preferable alternative. Inner circles are smaller than outer circles, so this chart may convey misleading information about data points. Also should not be used for more than 7 data series

Links

• Learn more about pie charts at Wikipedia.
• Read a warning against using pie charts