Teaching:TUW - UE InfoVis WS 2008/09 - Gruppe 07 - Aufgabe 1 - Pie Chart: Difference between revisions
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[[image:PiechartsAndBars.png| thumb | Comparison of Pie Chart vs. Bar Chart]] | [[image:PiechartsAndBars.png| thumb | Comparison of Pie Chart vs. Bar Chart]] |
Revision as of 19:47, 4 November 2008
Pie Charts
Definition
How to use it
Determine proportions. Find the total value for the entire category being studied and calculate the percentage for each segment or part.
Calculate degress. Convert the percentage values for each segment into degrees relative to the 360 degrees in the circle. (For example, 12% X 360 degrees = 43 degrees)
Construct the chart. Draw a circle and divide it into appropriately sized segments. Add labels and a title. Label each segment or add a legend to identify the segments. Then clearly title the chart.
Criticism on the Pie Chart
Though being a common method of displaying data, pie charts are not the preferred method among statisticians and in scientific literature. While pie charts offer a good view on how one segment is related to the whole pie the comparison of segments amongst each other is difficult. Also a comparison by angle (as in pie charts) was shown to be percieved less accurate than comparison by length. Using bars instead of slices improves therfore improves the capability to compare the different segments of data.
Example
Data
A student's life. Hours per week.
- Sleeping 40
- Partying 15
- Eating 10
- Slacking 20
- Working 30
- Studying 20
Other Forms of Charts
Among Pie Charts, used to display percentages, other forms of charts can be used for different purposes.
- Column Charts - Used to show comparisons between items of data. A column in the chart represents the value of one item of data.
- Bar Charts - Are very similar to column charts, except they run horizontally on the page instead of vertically like column charts.
- Line Charts - Used to show trends over time. Each line in the graph shows the changes in the value of one item of data.
References
- [Hull, 1998] Stephen Hull, BusinessObjects Glossary. Last Modified at: November 5, 1998. Retreived at: November 4, 2008 http://planning.ucsc.edu/IRPS/dwh/BOBGLOSS.HTM
- [Concordia University, 1999] Unknown, Pie Chart. Last Modified at: 1999. Retrieved at: November 4, 2008 http://web2.concordia.ca/Quality/tools/21piechart.pdf
- [French, 2008] Ted French. Chart. http://spreadsheets.about.com/od/c/g/chart_def.htm
- [Wikipedia, 2008] Wikipedia, http://en.wikipedia.org/wiki/Pie_chart