ABSTRACT

In presentation graphics, if the aim of the user is to show how various elements make up a whole, the best form is probably a pie chart. This type of chart is very useful when there are a small number of elements, usually four or five, but never more than eight. Pie charts rely on proportional area to denote quantity and therefore should be appropriate to the data, e.g. area or volume. The standard pie chart represents 100% of a statistic or other item of data. Each of the components of this total is computed as a percentage of the whole 360 degrees and converted to its appropriate segment of the circle. Thus the circle or pie, is divided by radial lines into sectors, so that the area of each sector is proportional to the quantity it represents. Because the pie or circular area chart relies upon immediate impressions, it is not successful when there are consider able variations in the size of the sectors. Pie charts are also not recommended if any of the sectors is less than 5%. For a large number of small data items, it is often better to combine them into one segment under an ‘Other’ label.