Chartjunk
If a categorical data set has only a few distinct categories, the information in it can be very simply expressed. For example, consider the gender of each student in a class of 160. The bar chart on the right only shows that there were 100 males, 62.5% of the class. |
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Since the information contained in a bar chart is often simple (only 2 values above), it is tempting to embellish bar charts 'artistically' to make them more visually appealing. These additions are collectively called chartjunk. Many spreadsheets, such as Microsoft Excel, make it easy to add chartjunk to bar charts.
In general, chartjunk should be avoided — it is usually easier to read information from a standard bar chart. Rather than adding chartjunk, draw the bar chart small or replace it with a frequency table.
Three-dimensional chartjunk
A common form of chartjunk is obtained by changing each bar into a 3-dimensional object. When the resulting 3-dimensional picture is rotated, it often becomes harder to compare the heights of bars and to read off values from the axes. In particular, perspective views should be avoided.
Kestrel causes of death
The diagram below was produced by Microsoft Excel to show the causes of death of kestrels in Britain.
Although this display is more visually appealing than the original barchart, it is now harder to assess whether the numbers dying from Trauma were just over or under 300.
Although the above barchart is still acceptable, the extra rotation and perspective viewpoint of the diagram below make it an extremely poor representation of the data.
Avoid drawing bar charts in 3-dimensions.