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A radar chart is a graphical method of displaying multivariate data in the form of a two-dimensional chart of three or more quantitative variables represented on axes starting from the same point. The relative position and angle of the axes is typically uninformative. The radar chart is also known as web chart, spider chart, star chart,〔Nancy R. Tague (2005) ''The quality toolbox''. page 437.〕 star plot, cobweb chart, irregular polygon, polar chart, or kiviat diagram.〔(Star Plots ) - Statistical Graphics for Multivariate Data〕 == Overview == The radar chart is a chart and/or plot that consists of a sequence of equi-angular spokes, called radii, with each spoke representing one of the variables. The data length of a spoke is proportional to the magnitude of the variable for the data point relative to the maximum magnitude of the variable across all data points. A line is drawn connecting the data values for each spoke. This gives the plot a star-like appearance and the origin of one of the popular names for this plot. The star plot can be used to answer the following questions:〔 * Which observations are most similar, i.e., are there clusters of observations? (Radar charts are used to examine the relative values for a single data point (e.g., point 3 is large for variables 2 and 4, small for variables 1, 3, 5, and 6) and to locate similar points or dissimilar points.)〔 * Are there outliers? Radar charts are a useful way to display multivariate observations with an arbitrary number of variables.〔Chambers, John, William Cleveland, Beat Kleiner, and Paul Tukey, (1983). ''Graphical Methods for Data Analysis''. Wadsworth. pp. 158-162〕 Each star represents a single observation. Typically, radar charts are generated in a multi-plot format with many stars on each page and each star representing one observation.〔NIST/SEMATECH (2003). (Star Plot ) in: ''e-Handbook of Statistical Methods''. 6/01/2003 (Date created)〕 The star plot was first used by Georg von Mayr in 1877.〔, p.78. Linien-Diagramme im Kreise: Line charts in circles.〕〔Michael Friendly (2008). ("Milestones in the history of thematic cartography, statistical graphics, and data visualization" ).〕 Radar charts differ from glyph plots in that all variables are used to construct the plotted star figure. There is no separation into foreground and background variables. Instead, the star-shaped figures are usually arranged in a rectangular array on the page. It is somewhat easier to see patterns in the data if the observations are arranged in some non-arbitrary order (if the variables are assigned to the rays of the star in some meaningful order).〔Michael Friendly (1991). ("Statistical Graphics for Multivariate Data" ). Paper presented at the SAS SUGI 16 Conference, Apr, 1991.〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Radar chart」の詳細全文を読む スポンサード リンク
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