Design Pattern: RM(13) Pie charts


A set of incoming alarms has been registered. The human operator would like to compare the number of alarms across different dimensions such as priority, typology or time.


The human operator needs to compare the distribution of alarm activations across different alarm dimensions in order to project future states of the controlled process.


Use pie charts to show this distribution. A pie chart is a circular object divided into multiple polar segments. It displays the relative magnitude of several quantitative values compared to each other. The full circle represents the total magnitude of this dataset, equal to 100 percent, while each segment stands for the magnitude of one particular variable. Segment area, are length and arc angle of each segment are proportional to the value the segment represents.

Known uses
Fig1. DeltaV system alarm statistics page (see a bar chart for alarm activation rates per device framed in red)
Fig2.IrisView system alarm dashboard which gives the operator a view of any alarms associated with the elements they are responsible for (see a pie chart for alarm distribution by severity framed in red)

Pie charts give the reader a quick idea of the proportional distribution of data. The association between data and representation is evident: the bigger the piece, the larger the data chunk compared to the other ones. (Bertini, E., Hertzog, P., & Lalanne, D. (2007). SpiralView: Towards security policies assessment through visual correlation of network resources with evolution of alarms. Paper presented at the Visual Analytics Science and Technology, 2007. VAST 2007. IEEE Symposium on, 139-146)