Pie chart of populations of English native speakers

A pie graph showing cement production

A pie chart (or a circle graph) is a circular chart divided into sectors, illustrating proportion. In a pie chart, the arc length of each sector (and consequently its central angle and area), is proportional to the quantity it represents. When angles are measured with 1 turn as unit then a number of percent is identified with the same number of centiturns. Together, the sectors create a full disk. It is named for its resemblance to a pie which has been sliced. The earliest known pie chart is generally credited to William Playfair's Statistical Breviary of 1801.^[1][2]

The pie chart is perhaps the most widely used statistical chart in the business world and the mass media.^[3] However, it has been criticized,^[4] and some recommend avoiding it,^[5][6][7][8] pointing out in particular that it is difficult to compare different sections of a given pie chart, or to compare data across different pie charts. Pie charts can be an effective way of displaying information in some cases, in particular if the intent is to compare the size of a slice with the whole pie, rather than comparing the slices among them.^[1] Pie charts work particularly well when the slices represent 25 to 50% of the data,^[9] but in general, other plots such as the bar chart or the dot plot, or non-graphical methods such as tables, may be more adapted for representing certain information. It also shows the frequency within certain groups of information.

Example[link]

A pie chart for the example data.

The following example chart is based on preliminary results of the election for the European Parliament in 2004. The table lists the number of seats allocated to each party group, along with the derived percentage of the total that they each make up. The values in the last column, the derived central angle of each sector, is found by multiplying the percentage by 360°.

Use, effectiveness and visual perception[link]

Three sets of data plotted using pie charts and bar charts.

Pie charts are common in journalism^{[citation needed]}. However, 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 when area is used instead of length and when different items are shown as different shapes.

Further, in research performed at AT&T Bell Laboratories, it was shown that comparison by angle was less accurate than comparison by length. This can be illustrated with the diagram to the right, showing three pie charts, and, below each of them, the corresponding bar chart representing the same data. Most subjects have difficulty ordering the slices in the pie chart by size; when the bar chart is used the comparison is much easier.^[10] 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.^[11]

However, the research of Spence and Lewandowsky did not find pie charts to be inferior.^[12][13] Participants were able to estimate values with pie charts just as well as with other presentation forms.

Variants and similar charts[link]

Exploded pie chart[link]

An exploded pie chart for the example data, 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[link]

"Diagram of the causes of mortality in the army in the East" by Florence Nightingale.

The polar area diagram is similar to a usual pie chart, except sectors are 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., count of deaths by month). For example, if the count 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 count for the month, so the area of a sector represents the number of deaths in a month. If the death count in each month is subdivided by cause of death, it is possible to make multiple comparisons on one diagram, as is clearly seen in the form of polar area diagram famously developed by Florence Nightingale.

The first known use of polar area diagrams was by André-Michel Guerry, which he called courbes circulaires, in an 1829 paper showing seasonal and daily variation in wind direction over the year and births and deaths by hour of the day.^[14] 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 meteorologists. Nightingale published her rose diagram in 1858. The name "coxcomb" is sometimes used erroneously: this was the name Nightingale used to refer to a book containing the diagrams rather than the diagrams themselves.^[15] It has been suggested^{[by whom?]} that most of Nightingale's early reputation was built on her ability to give clear and concise presentations of data.

Spie chart[link]

A useful variant of the polar area chart is the spie chart designed by Feitelson .^[16] This superimposes a normal pie chart with a modified polar area chart to permit the comparison of a set of data at two different states. For the first state's budget distribution, this is useful for visualizing hazards for population groups (e.g. the distribution of age and gener groups among road casualties compared with these groups's sizes in the general population). The R Graph Gallery provides an example.^[17]

Multi-level Pie, Radial tree, or Ring chart[link]

Multi-level pie or Ring chart of Disk usage in Linux file system

Multi-level pie chart, also known as a radial tree chart is used to visualize hierarchical data, depicted by concentric circles.^[18] The circle in the centre 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.^[19]

3-D pie chart[link]

A perspective (3D) pie chart is used to give the chart a 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 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.^[7][20]

Doughnut chart[link]

A doughnut chart (also spelled donut) is functionally identical to a pie chart, with the exception of a blank center and the ability to support multiple statistics as one.

History[link]

The earliest known pie chart is generally credited to William Playfair's Statistical Breviary of 1801, in which two such graphs are used.^[1][2] This invention was not widely used at first;^[1] the French engineer Charles Joseph Minard was one of the first to use it in 1858, in particular in maps where he needs to add information in a third dimension.^[21] It has been said that Florence Nightingale invented it, though in fact she just popularised it and she was later assumed to have created it due to the obscurity of Playfair's creation.^[22]

• 

  One of William Playfair's pie charts in his Statistical Breviary, depicting the proportions of the Turkish Empire located in Asia, Europe and Africa before 1789.

• 

  Minard's map using pie charts to represent the cattle sent from all around France for consumption in Paris (1858).

Notes[link]

References[link]

A slice of an apple pie

A pie is a baked dish which is usually made of a pastry dough casing that covers or completely contains a filling of various sweet or savoury ingredients.

Pies are defined by their crusts. A filled pie (also single-crust or bottom-crust), has pastry lining the baking dish, and the filling is placed on top of the pastry, but left open. A top-crust pie, which may also be called a cobbler, has the filling in the bottom of the dish and the filling covered with a pastry or other covering before baking. A two-crust pie has the filling completely enclosed in the pastry shell. Flaky pastry is a typical kind of pastry used for pie crusts, but many things can be used, including baking powder biscuits, mashed potatoes, and crumbs.

Pies can be a variety of sizes, ranging from bite-size to ones designed for multiple servings.

History[link]

Homemade meat pie with beef and vegetables.

A slice of pecan pie

A 19th-century pie crimper made of ivory, in the collection of The Children's Museum of Indianapolis

Jeûne Genevois plum pie

A chicken pie with a traditional pie bird

The need for nutritious, easy-to-store, easy-to-carry, and long-lasting foods on long journeys, in particular at sea, was initially solved by taking live food along with a butcher or cook. However, this took up additional space on what were either horse-powered treks or small ships, reducing the time of travel before additional food was required. This resulted in early armies adopting the style of hunter-foraging.

The introduction of the baking of processed cereals including the creation of flour, provided a more reliable source of food. Egyptian sailors carried a flat brittle bread loaf of millet bread called dhourra cake, while the Romans had a biscuit called buccellum.^[1]

The first pies appeared around 9500 BC, in the Egyptian Neolithic period or New Stone Age, when the use of stone tools shaped by polishing or grinding became common, the domestication of plants and animals, the establishment of permanent villages, and the practice of crafts such as pottery and weaving. Early pies were in the form of galettes wrapping honey as a treat inside a cover of ground oats, wheat, rye or barley. These galettes developed into a form of early sweet pastry or desserts, evidence of which can be found on the tomb walls of the Pharaoh Ramesses II, who ruled from 1304 to 1237 BC, located in the Valley of the Kings.^[2] Sometime before 2000 BC, a recipe for chicken pie was written on a tablet in Sumer.^[3]

With the knowledge transferred to the Ancient Greeks, historians believe that the Greeks originated pie pastry. Then a flour-water paste (add fat, and it becomes pastry),^[4] wrapped around meat, served to: cook the meat; seal in the juices; and provide a lightweight sealed holder for long sea journeys. This transferred the knowledge to the Romans who, having conquered parts of Northern Europe and southern Spain were far more adept at using salt and spices to preserve and flavour their meat.^[2]

The 1st century Roman cookbook Apicius make various mention of various recipes which involve a pie case.^[5] By 160 BC, Roman statesman Marcus Porcius Cato (234-149 BC) who wrote De Agri Cultura, notes the recipe for the most popular pie/cake called Placenta. Also called libum by the Romans, it was more like a modern day cheesecake on a pastry base, often used as an offering to the gods. With the development of the Roman Empire and its efficient road transport, pie cooking spread throughout Europe.^[2]

Pies remained as a core staple of diet of traveling and working peoples in the colder northern European countries, with regional variations based on both the locally grown and available meats, as well as the locally farmed cereal crop. The Cornish pasty is an excellent adaptation of the pie to a working man's daily food needs.^[2]

Medieval cooks were often restricted in cooking forms they were able to use, having restricted access to ovens due to their costs of construction and need for abundant supplies of fuel. Pies could be easily cooked over an open fire, while partnering with a baker allowed them to cook the filling inside their own locally defined casing. The earliest pie-like recipes refer to coffyns (the word actually used for a basket or box), with straight sealed sides and a top; open top pies were referred to as traps. This may also be the reason why early recipes focus on the filling over the surrounding case, with the partnership development leading to the use of reusable earthenware pie cases which reduced the use of expensive flour.^[6]

The first reference to "pyes" as food items appeared in England (in a Latin context) as early as the 12th century, but no unequivocal reference to the item with which the article is concerned is attested until the 14th century (Oxford English Dictionary sb pie).^[2]

Song birds at the time were a fine delicacy, and protected by Royal Law. At the coronation of eight-year old English King Henry VI (1422–1461) in 1429, "Partryche and Pecock enhackyll" pie was served, consisting of cooked peacock mounted in its skin on a peacock filled pie. Cooked birds were frequently placed by European royal cooks on top of a large pie to identify its contents, leading to its later adaptation in pre-Victorian times as a porcelain ornament to release of steam and identify a good pie.^[2]

The Pilgrim fathers and early settlers brought their pie recipes with them to America, adapting to the ingredients and techniques available to them in the New World. Their first pies were based on berries and fruits pointed out to them by the Native North Americans.^[2] Pies allowed colonial cooks to stretch ingredients and also used round shallow pans to literally "cut corners," and create a regional variation of shallow pie.^[7]

Regional variations[link]

Apple pie crust

Meat pies with fillings such as steak, cheese, steak and kidney, minced beef, or chicken and mushroom are popular in the United Kingdom,^[8] Australia and New Zealand as take-away snacks. They are also served with chips as an alternative to fish and chips at British chip shops.

Pot pies with a flaky crust and bottom are also a popular American dish, typically with a filling of meat (particularly beef, chicken or turkey), gravy, and mixed vegetables (potatoes, carrots and peas). Frozen pot pies are often sold in individual serving size.

Fruit pies may be served with a scoop of ice cream, a style known in North America as pie à la mode. Many sweet pies are served this way. Apple pie is a traditional choice, though any pie with sweet fillings may be served à la mode. This combination, and possibly the name as well, is thought to have been popularized in the mid-1890s in the United States.^[9]

Pie throwing[link]

Cream filled or topped pies are favorite props for humor. Throwing a pie in a person's face has been a staple of film comedy since Ben Turpin received one in Mr. Flip in 1909.^[10] More recently, pieing has also become a political act.

Types of pies[link]

Savory pies[link]

Sweet pies[link]

Some of these pies are pies in name only, such as the Boston cream pie, which is a cake. Many fruit and berry pies are very similar, varying only the fruit used in filling. Fillings for sweet or fruity are often mixed, such as strawberry rhubarb pie.

See also[link]

Food portal

References[link]

External links[link]

Wikimedia Commons has media related to: Pie

Look up pie in Wiktionary, the free dictionary.

Wikibooks Cookbook has a recipe/module on Pie

• A Tale of Two Tarts by Monica Gaudio (contains info that can be added into article with references)
• Food Timeline, History Notes: Pie & Pastry
• The American Pie Council
• A Wide Variety of Pie Recipes at recipeforpie.com

A pie chart.

A chart is a graphical representation of data, in which "the data is represented by symbols, such as bars in a bar chart, lines in a line chart, or slices in a pie chart".^[1] A chart can represent tabular numeric data, functions or some kinds of qualitative structures.

The term "chart" as a graphical representation of data has multiple meanings:

• A data chart is a type of diagram or graph, that organizes and represents a set of numerical or qualitative data.
• Maps that are adorned with extra information for some specific purpose are often known as charts, such as a nautical chart or aeronautical chart.
• Other domain specific constructs are sometimes called charts, such as the chord chart in music notation or a record chart for album popularity.

Charts are often used to ease understanding of large quantities of data and the relationships between parts of the data. Charts can usually be read more quickly than the raw data that they are produced from. They are used in a wide variety of fields, and can be created by hand (often on graph paper) or by computer using a charting application. Certain types of charts are more useful for presenting a given data set than others. For example, data that presents percentages in different groups (such as "satisfied, not satisfied, unsure") are often displayed in a pie chart, but may be more easily understood when presented in a horizontal bar chart.^[2] On the other hand, data that represents numbers that change over a period of time (such as "annual revenue from 1990 to 2000") might be best shown as a line chart.

Features of a chart[link]

A chart can take a large variety ; however, there are common features that provide the chart with its ability to extract meaning from data.

Typically a chart is graphical, containing very little text, since humans are generally able to infer meaning from pictures quicker than from text. One of the more important uses of text in a graph is in the title. A graph's title usually appears above the main graphic and provides a succinct description of what the data in the graph refers to.

Dimensions in the data are often displayed on axes. If a horizontal and a vertical axis are used, they are usually referred to as the x-axis and y-axis respectively. Each axis will have a scale, denoted by periodic graduations and usually accompanied by numerical or categorical indications. Each axis will typically also have a label displayed outside or beside it, briefly describing the dimension represented. If the scale is numerical, the label will often be suffixed with the unit of that scale in parentheses. For example, "Distance traveled (m)" is a typical x-axis label and would mean that the distance travelled in metres is related to the horizontal position of the data.

Within the graph a grid of lines may appear to aid in the visual alignment of data. The grid can be enhanced by visually emphasizing the lines at regular or significant graduations. The emphasized lines are then called major grid lines and the rest of the grid lines are minor grid lines.

The data of a chart can appear in all manner of formats, with or without individual labels. It may appear as dots or shapes, connected or unconnected, and in any combination of colors and patterns. Inferences or points of interest can be overlayed directly on the graph to further aid information extraction.

When the data appearing in a chart contains multiple variables, the chart may include a legend. A legend contains a list of the variables appearing in the chart and an example of their appearance. This information allows the data from each variable to be identified in the chart.

Types of charts[link]

Common charts[link]

Four of the most common charts are:

• 

  Histogram

• 

  Bar chart

• 

  Pie chart

• 

  Line chart

This gallery shows:

• A histogram consists of tabular frequencies, shown as adjacent rectangles, erected over discrete intervals (bins), with an area equal to the frequency of the observations in the interval.
• A bar chart is a chart with rectangular bars with lengths proportional to the values that they represent. The bars can be plotted vertically or horizontally.
• A pie chart shows percentage values as a slice of a pie.
• A line chart is a two-dimensional scatterplot of ordered observations where the observations are connected following their order.

Other common charts are:

• 

  Timeline chart

• 

  Organizational chart

• 

  Tree chart

• 

  Flow chart

• 

  Area chart

• 

  Cartogram

• 

  Pedigree chart

Less-common charts[link]

Examples of less common charts are:

• 

  Bubble chart

• 

  Polar area diagram

• Waterfall-chart.jpg

  Waterfall chart

• 

  Radar chart

• 

  Tree map

This gallery shows:

• A bubble chart is a two-dimensional scatterplot where a third variable is represented by the size of the points.
• A Polar area diagram, sometimes called a Coxcomb chart, is an enhanced form of pie chart developed by Florence Nightingale.
• A radar chart or "spider chart" is a two-dimensional chart of three or more quantitative variables represented on axes starting from the same point.
• A waterfall chart also known as a "Walk" chart, is a special type of floating-column chart.
• A Tree Map where the areas of the rectangles correspond to values. Other dimensions can be represented with colour or hue.

Field-specific charts[link]

Some types of charts have specific uses in a certain field

• 

  Open-high-low-close chart

• Candlestick-chart.png

  Candlestick chart

• 

  Kagi chart

• 

  Sparkline

This gallery shows:

• Stock market prices are often depicted with a open-high-low-close chart with a traditional bar chart of volume at the bottom.
• Candlestick charts are another type of bar chart used to describe price movements of an equity over time.
• A Kagi chart is a time-independent stock tracking chart that attempts to minimise noise.
• Alternatively, where less detail is required, and chart size is paramount, a Sparkline may be used.

Other examples:

• Interest rates, temperatures, etc., at the close of the period are plotted with a line chart.
• Project planners use a Gantt chart to show the timing of tasks as they occur over time.

Well-known named charts[link]

Some of the better-known named charts are:

• 

  Gantt chart

• 

  Nolan chart

• 

  PERT chart

• 

  Smith chart

Some specific charts have become well known by effectively explaining a phenomenon or idea.

• An Allele chart is a chart originating from the study of genetics to show the interaction of two data points in a grid.
• A Gantt chart helps in scheduling complex projects.
• The Nolan chart and the Pournelle chart classify political philosophies according to two axes of variation.
• A PERT chart is often used in project management.
• The Smith chart serves in radio electronics.

Other charts[link]

There are dozens of other types of charts. Here are some of them:

• 

  Control chart

• 

  Natal chart

• 

  Nomogram

• 

  Pareto chart

• 

  Run chart

• 

  Structure chart

• 

  Vowel chart

• 

  Strip chart

• 

  Heatmap

Common plots[link]

• 

  Box plot

• 

  Dot plot (statistics)

• 

  Probability plot

• 

  Scatterplot

• 

  Biplot

Chart Software[link]

There are many different types of software available to produce charts.

JavaScript[link]

• D3.js - HTML5/CSS3/SVG, BSD license
• JS InfoVis Toolkit - HTML5/SVG, MIT license
• Envision.js - HTML5, MIT license
• Sencha ExtJS 4 Charts - HTML5/SVG/Canvas, GPL or Commercial license
• Sencha Touch Charts - HTML5/SVG/Canvas, GPL or Commercial license

Excel[link]

• Microsoft Excel - Built in charting function for basic chart types

Java[link]

• JFreeChart - Free Java based chart software

Flash[link]

• AnyChart - Cross browser / Cross platform / Flash/JavaScript (HTML5) / Multiple data input / Variety of chart output / AnyChart Free Trial / AnyChart Full Version Purchase
• FusionCharts - Cross browser / Cross server-side technologies / Flash/JavaScript (HTML5) / Multiple mobile devices / Variety of chart output /

See also[link]

Wikimedia Commons has media related to: Chart

• Diagram
• Edward Tufte
• Exploratory data analysis
• Information graphics
• Graphic organizer
• Mathematical diagram
• Official statistics
• Plot (graphics)
• Comparison of Adobe Flex charts

References[link]

This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (October 2008)