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From Wikipedia

Pie chart

A pie chart (or a circle graph) is a circularchart 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.

The pie chart is perhaps the most ubiquitous statistical chart in the business world and the mass media. However, it has been criticized, and some recommend avoiding it, 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. Pie charts work particularly well when the slices represent 25 to 50% of the data, 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

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 360Â°.

*Because of rounding, these totals do not add up to 100 and 360.

The size of each central angle is proportional to the size of the corresponding quantity, here the number of seats. Since the sum of the central angles has to be 360Â°, the central angle for a quantity that is a fraction Q of the total is 360Q degrees. In the example, the central angle for the largest group (European People's Party (EPP)) is 135.7Â° because 0.377 times 360, rounded to one decimal place(s), equals 135.7.

Use, effectiveness and visual perception

Pie charts are common in business and journalism, perhaps because they are perceived as being less "geeky" than other types of graph. 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. Stevens' power law states that visual area is perceived with a power of 0.7, compared to a power of 1.0 for length. This suggests that length is a better scale to use, since perceived differences would be linearly related to actual differences.

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.. 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.

Variants and similar charts

Polar area diagram

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 AndrÃ©-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. LÃ©on 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. It has been suggested that most of Nightingale's early reputation was built on her ability to give clear and concise presentations of data.

Spie chart

A useful variant of the polar area chart is the spie chart designed by Feitelson . 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, for example time 1, a normal pie chart is drawn. For the second state, the angles of the slices are the same as in the original pie chart, and the radii vary according to the change in the value of each variable. In addition to comparing a partition at two times (e.g. this year's budget distribution with last year'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.

Multi-level pie chart

Multi-level pie chart, also known as a radial tree c

Question:What fraction of the speed of light must an authentic meter stick (proper length) be moving past you to measure its length as 9.2 cm?

Answers:The equation for length dilation is L = L0 (1 - v /c ) where c is light speed, v is the speed of the meter stick, L0 is the original length (1 m = 100 cm) and L is the observed length (9.2 cm). 9.2 = 100 (1 - v /c ) 0.092 = (1 - v /c ) 0.092 = 1 - v /c v /c = 1 - 0.092 = 1 - 0.008464 = 0.991536 v/c = 0.991536 = 0.995759 So the speed of the stick is v = 0.995759c

Question:I am looking for a chart that I can print, or something along that line, that states the general algebra rules, like a positive + a positive = a positive. A negative + a negative = a negative. Positive x Negative = blah blah. Negative - a positive = blah blah. I am constantly getting confused about addition, subtraction, multiplying and division of fractions, integers, positives and negatives. I want to try to find a chart that I can print up that will give me a quit reference! Any websites you know of?? THANKS!

Question:You can make healthy meals for your family. with an Acid Alkaline Food Chart? Question: Lately I have been hearing so much about The Alkaline Diet and how it will prevent diseases, including cancer, and is a healthy way of eating. What foods promote alkalinity, and which foods do I stay away from? Can you help me?

Answers:An acid alkaline food chart shows which food category that you should choose your foods from. The alkaline diet is not a diet like counting calories or carbs. It is about using an acid alkaline food chart, so that you can select the alkaline foods and prepare healthy meals with them. Here is a list of the foods. Alkaline Foods All fruits All vegetables Most Seeds and nuts including pumpkin, sesame, flax, almonds, lentils and legumes Drinks water, pure 100% juices, fresh juice, soy milk, almond milk, rice milk, and all herbal teas. Soy flour, whey protein, yogurt Fats and Oils olive, flax, evening primrose, coconut Acidic Foods Most oils All dairy All animal proteins All Pastas All alcohol All chemicals, including prescriptions Bread, coffee, sugars, all soft drinks, condiments Full chart: http://www.acidalkalinediet.com/Alkaline-Foods-Chart.htm From an acid alkaline food chart or list, take 80% of you daily foods from the alkaline foods and 20% from the acidic foods on the chart. By eating this way you will create healthy meals for your family and every time you stick to the 80/20 rule you ll know you are adding more protection from cancer and the other diseases.

Question:like which topic are they classified under. Because at school kids get more than 1. like not just rational, but natural too i just don't understand the number chart like say 3.45 and 3/45 (that slash is a fraction bar)

Answers:They go under the RATIONAL.| what grade r u in cause im in the 7th and i have a whole lot of stuff for the real number system/chart.|Email me if u need anything (im kinda a nerdy jock)

"1 to 100" and "101 to 200" Charts Math in Color :mathincolor.com $20 for a class set of 4 posters and 60 handouts with shipping included. A brief explantion of how to use the math aid Math in Color 1 to 100 and 101 to 200 charts to understand (and memorize) multiplication, division, factors, multiples,prime, LCM, GCF, fractions... Go to the website and click on "connections to math standards" to see 37 standards this helps with, "how it works" for how it works, and "free worksheets" for how it can be used with paper assignments. Explained by Chris Hansen. Filmed and edited by Tony Rodebaugh. A set of 4 posters and 60 handouts is available at mathincolor.com for$20.