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A pie chart (or a circle graph) is a circular chart divided into sectors, illustrating relative magnitudes or frequences or percents. In a pie chart, the arc length of each sector (and consequently its central angle and area), is proportional to the quantity it represents. Together, the sectors create a full disk. It is named for its resemblance to a pie which has been sliced. While the pie chart is perhaps the most ubiquitous statistical chart in the business world and the mass media, it is rarely used in scientific or technical publications.[1] It is one of the most widely criticised charts,[2] and many statisticians recommend to avoid its use altogether[3][4], 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.[5] Pie charts work particularly well when the slices represent 25 or 50% of the data,[6] 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 information. The earliest known pie chart is generally credited to William Playfair's Statistical Breviary of 1801.[7][5] The following example chart is based on preliminary results of the election for the European Parliament in 2004. The following 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°.
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