Other displays of categorical data
Two variations of the standard bar chart of categorical data are often encountered. A stacked bar chart is simply a bar chart in which the bars are stacked on top of each other. Stacked bar charts are often used to compare two or more groups of individuals.
In a pie chart, a circle is split into segments according to the proportion of data values in each category. The angle for each category is given by the proportion.
Although pie charts seem visually different from the two types of bar chart, they are closely related.
In bar charts, stacked bar charts and pie charts, the area of ink for any category is proportional to the number of values in that category
Story completion
The bar chart below is based on a table published by the New Zealand National Education Monitoring Unit describing the originality of a story-completion exercise by 1440 Year 4 students. (Each child was asked to supply an ending to a story.)
Drag the slider to the right to stack the bars of the bar chart.
In the diagram below, drag the slider to change the stacked bar chart into a pie chart.