One reason for this may be 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. Pie charts are rare in the scientific literature, but are more common in business and economics. Pie charts should be used only when the sum of all categories is meaningful, for example if they represent proportions. The same data plotted using a pie chart and a bar chart. In the example, the central angle for the largest group (EPP) is 135.7° because 0.377 times 360, rounded to one decimal place, equals 135.7. Since the sum of the central angles has to be 360°, the central angle for a quantity that is a fraction Q of the total is 360 Q degrees. The size of each central angle is proportional to the size of the corresponding quantity, here the number of seats. *Because of rounding, these totals do not add up to 100 and 360. The values in the last column, the central angle of each sector, is found by multiplying the percentage by 360°.
The following table lists the number of seats allocated to each party group, along with the percentage of the total that they each make up.
The following example chart is based on preliminary results of the election for the European Parliament in 2004. The earliest known pie chart is generally credited to William Playfair's Statistical Breviary of 1801.Īn exploded pie chart for the example data, with the largest party group exploded. While pie charts can be an effective way of displaying information in some cases, in particular when the slices represent 25 or 50% of the data, in general, other plots such as the bar chart or the dot chart are more adapted for representing information. It is one of the most widely criticised charts, and many statisticians recommend to avoid its use altogether, 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. 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.
One of William Playfair's piechart in his Statistical Breviary A chart with one or more sectors separated from the rest of the disk is called an exploded pie chart. Together, the sectors create a full disk. In a pie chart, the arc length of each sector (and consequently its central angle and area), is proportional to the quantity it represents. A pie chart is a circular chart divided into sectors, illustrating relative magnitudes or frequencies.
0 kommentar(er)
