Editing Pie chart (section)

==Use and effectiveness==
[[File:Atmospheric air components percentage.jpg|thumb|left|3D pie chart showing Atmospheric air components percentage]]
A flaw exhibited by pie charts is that they cannot show more than a few values without separating the visual encoding (the “slices”) from the data they represent (typically percentages). When slices become too small, pie charts have to rely on colors, textures or arrows so the reader can understand them. This makes them unsuitable for use with larger amounts of data. Pie charts also take up a larger amount of space on the page compared to the more flexible bar charts, which do not need to have separate legends, and can display other values such as averages or targets at the same time.<ref name="sfew" />

[[Statisticians]] generally regard pie charts as a poor method of displaying information, and they are uncommon in scientific literature. One reason is that it is more difficult for comparisons to be made between the size of items in a chart [[Stevens' power law|when area is used instead of length]] and when different items are shown as different shapes.<ref>{{cite web |last1=Krygier |first1=John |title=Perceptual Scaling of Map Symbols |url=http://makingmaps.net/2007/08/28/perceptual-scaling-of-map-symbols/ |website=makingmaps.net |date=28 August 2007 |access-date=3 May 2015}}</ref>

[[File:Piecharts.svg|thumb|right|Three sets of percentages, plotted as both piecharts and barcharts. Comparing the data on barcharts is generally easier.]]
Further, in research performed at [[AT&T Bell Laboratories]], it was shown that comparison by angle was less accurate than comparison by length. Most subjects have difficulty ordering the slices in the pie chart by size; when an equivalent bar chart is used the comparison is much easier.<ref name="cleveland85">Cleveland, p. 86–87</ref> Similarly, comparisons between data sets are easier using the bar chart. However, if the goal is to compare a given category (a slice of the pie) with the total (the whole pie) in a single chart and the multiple is close to 25 or 50 percent, then a pie chart can often be more effective than a bar graph.<ref>Simkin, D., & Hastie, R. (1987). An Information-Processing Analysis of Graph Perception. Journal of the American Statistical Association, 82(398), 454. {{doi|10.2307/2289447}}. {{cite web |last=Kosara |first=Robert |title=In Defense of Pie Charts |date=13 April 2011 |url=http://eagereyes.org/criticism/in-defense-of-pie-charts |access-date=April 13, 2011}}</ref><ref name="spence91" >{{cite journal |last=Spence |first=Ian |author2=Lewandowsky, Stephan |title=Displaying proportions and percentages |journal=Applied Cognitive Psychology |date=1 January 1991 |volume=5 |issue=1 |pages=61–77 |doi=10.1002/acp.2350050106}}</ref>

[[Image:Badpie.png|thumb|left|An example of a pie chart with 18 values, with some colors repeated]]
In a pie chart with many section, several values may be represented with the same or similar colors, making interpretation difficult.

[[Image:Doughnut shape Pie Chart.jpg|thumb|right|An example of a doughnut shape pie chart, showing the batting and run records of Indian cricket players in test matches in 2019]]
Several studies presented at the ''European Visualization Conference'' analyzed the relative accuracy of several pie chart formats,<ref>{{Cite news|url=https://eagereyes.org/blog/2016/an-illustrated-tour-of-the-pie-chart-study-results|title=An Illustrated Tour of the Pie Chart Study Results|date=2016-06-28|newspaper=eagereyes|language=en-US|access-date=2016-11-28}}</ref><ref>{{Cite journal|last1=Skau|first1=Drew|last2=Kosara|first2=Robert|year=2016|title=Arcs, Angles, or Areas: Individual Data Encodings in Pie and Donut Charts|url=http://kosara.net/publications/Skau-EuroVis-2016.html|journal=EuroVis}}</ref><ref name=":0">{{Cite journal|last1=Kosara|first1=Robert|last2=Skau|first2=Drew|year=2016|title=Judgment Error in Pie Chart Variations|url=http://kosara.net/publications/Kosara-EuroVis-2016.html|journal=EuroVis}}</ref> reaching the conclusion that pie charts and doughnut charts produce similar error levels when reading them, and square pie charts provide the most accurate reading.<ref>{{Cite news|url=https://eagereyes.org/blog/2016/a-reanalysis-of-a-study-about-square-pie-charts-from-2009|title=A Reanalysis of A Study About (Square) Pie Charts from 2009|date=2016-07-11|newspaper=eagereyes|language=en-US|access-date=2016-11-28}}</ref> 
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