Editing Pie chart (section)

==Variants and similar charts==
[[File:misleading_macworld_3d_pie_chart.svg|thumb|upright|In a redrawing of the perspective pie chart shown at [[Macworld/iWorld#2008|MacWorld 2008]] (top), the smaller '''Apple''' slice appears larger than the '''Other''' slice &ndash; the 2D pie chart (bottom) gives the true picture]]
==={{anchor|Perspective}}3D pie chart and perspective pie cake===
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A 3D pie chart, or perspective pie chart, is used to give the chart a [[Three-dimensional space|3D]] look. Often used for aesthetic reasons, the third dimension does not improve the reading of the data; on the contrary, these plots are difficult to interpret because of the distorted effect of [[Perspective (visual)|perspective]] associated with the third dimension. The use of superfluous dimensions not used to display the data of interest is discouraged for charts in general, not only for pie charts.<ref name="sfew" /><ref>Good and Hardin, chapter 8.</ref>

===Doughnut chart===
{{float right clear none|[[File:Example of a doughnut chart.png|thumb|Information about the data as a whole in the center of a doughnut chart]]}}
A doughnut chart (also spelled donut) is a variant of the pie chart, with a blank center allowing for additional information about the data as a whole to be included.
<ref>{{cite book|last1=Harris|first1=Robert L.|title=Information graphics : a comprehensive illustrated reference|date=1999|publisher=Oxford University Press|location=Oxford|isbn=9780195135329|pages=143|edition=[Nachdr.]}}</ref><ref name="iTunes">{{Cite book|url=https://books.apple.com/us/book/id1178532425|title=Data Design by Juergen Kai-Uwe Brock on iBooks|website=iBooks|date=21 December 2016 |language=en|access-date=2017-06-10}}</ref> Doughnut charts are similar to pie charts in that their aim is to illustrate proportions.{{citation needed|date=October 2017}} This type of circular graph can support multiple statistics at once and it provides a better data intensity ratio to standard pie charts.<ref name="iTunes"/> It does not have to contain information in the center.

===Exploded pie chart===
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[[Image:Pie chart EP election 2004 exploded.png|thumb|150px|left|Exploded pie chart for the example data (see below), with the largest party group exploded.]]
A chart with one or more sectors separated from the rest of the disk is known as an ''exploded pie chart''. This effect is used to either highlight a sector, or to highlight smaller segments of the chart with small proportions.

===Polar area diagram===
[[Image:Nightingale-mortality.jpg|thumb|"''Diagram of the causes of mortality in the army in the East''" by Florence Nightingale.]]
[[File:2019 Carbon dioxide emissions by income group - Oxfam data.svg|thumb|Like conventional pie charts, a variable-radius pie chart has wedges whose areas represent  ''total'' quantities in respective categories/groups. However, here, each radius represents an amount of that quantity ''per unit'' within that category. In this example, each wedge's area represents total {{CO2}} emissions of all people in that category, and each radius represents emissions ''per person'' within that category.]]
The polar area diagram is similar to a usual pie chart, except sectors have equal angles and differ rather in how far each sector extends from the center of the circle.
The polar area diagram is used to plot cyclic phenomena (e.g., counts of deaths by month).
For example, if the counts of deaths in each month for a year are to be plotted then there will be 12 sectors (one per month) all with the same angle of 30 degrees each. The radius of each sector would be proportional to the square root of the death rate for the month, so the area of a sector represents the rate of deaths in a month.
If the death rate in each month is subdivided by cause of death, it is possible to make multiple comparisons on one diagram, as is seen in the polar area diagram famously developed by [[Florence Nightingale]].

The first known use of polar area diagrams was by [[André-Michel Guerry]], which he called {{lang|fr|courbes circulaires}} (circular curves), in an 1829 paper showing seasonal and daily variation in wind direction over the year and births and deaths by hour of the day.<ref name="Friendly, p. 509">Friendly, p. 509</ref> [[Léon Lalanne]] later used a polar diagram to show the frequency of wind directions around compass points in 1843. The [[wind rose]] is still used by [[meteorologist]]s. Nightingale published her rose diagram in 1858. Although the name "coxcomb" has come to be associated with this type of diagram, Nightingale originally used the term to refer to the publication in which this diagram first appeared—an attention-getting book of charts and tables—rather than to this specific type of diagram.<ref>{{cite web | url=http://www.florence-nightingale-avenging-angel.co.uk/GraphicsPaper/Graphics.htm | title=Florence Nightingale's Statistical Diagrams | access-date=2010-11-22}}</ref>

==={{anchor|Ring}}Ring chart, sunburst chart, and multilevel pie chart===
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[[Image:Disk usage (Boabab).png|thumb|right|Multi-level pie chart representing disk usage in a [[Linux]] file system]]
{{See also|Radial tree}}
A ring chart, also known as a [[sunburst]] chart or a multilevel pie chart, is used to visualize hierarchical data, depicted by concentric circles.<ref>{{Cite web|url=http://www.neoformix.com/2006/MultiLevelPieChart.html|title=Multi-level Pie Charts|website=www.neoformix.com}}</ref> The circle in the center represents the root node, with the hierarchy moving outward from the center. A segment of the inner circle bears a hierarchical relationship to those segments of the outer circle which lie within the angular sweep of the parent segment.<ref>Webber Richard, Herbert Ric, Jiangbc Wel. "Space-filling Techniques in Visualizing Output from Computer Based Economic Models"</ref>

===Spie chart===
[[Image:Spie_chart_001.png|thumb|left|A spie chart comparing number of students with student costs across four different schools]]
A variant of the polar area chart is the spie chart, designed by Dror Feitelson.<ref name="spie">{{cite web|url=http://www.cs.huji.ac.il/~feit/papers/Spie03TR.pdf|title=Feitelson, Dror (2003) Comparing Partitions With Spie Charts|year=2003|access-date=2010-08-31}}</ref>
The design superimposes a normal pie chart with a modified polar area chart to permit the comparison of two sets of related data. 
The base pie chart represents the first data set in the usual way, with different slice sizes. The second set is represented by the superimposed polar area chart, using the same angles as the base, and adjusting the radii to fit the data. For example, the base pie chart could show the distribution of age and gender groups in a population, and the overlay their representation among road casualties. Age and gender groups that are especially susceptible to being involved in accidents then stand out as slices that extend beyond the original pie chart.

=== Square chart / Waffle chart===
[[File:Square Pie Chart - Waffle Chart.jpg|thumb|Square pie chart (waffle chart), showing how smaller percentages are more easily shown than on circular charts. On the 10x10 grid, each cell represents 1%.]]
Square charts, also called waffle charts, are a form of pie charts that use squares instead of circles to represent percentages. Similar to basic circular pie charts, square pie charts take each percentage out of a total 100%. They are often 10 by 10 grids, where each cell represents 1%. Despite the name, circles, pictograms (such as of people), and other shapes may be used instead of squares. One major benefit to square charts is that smaller percentages, difficult to see on traditional pie charts, can be easily depicted.<ref name=":0" />