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The Ratio Average () plot is an integer based version of an MA plot for visualizing two-condition count data. Its distinctive arrow-like shape derives from the way it includes condition-unique (0,n) or (n,0) points into the plot via an epsilon factor. ==Definition== An RA plot, like its cousin, the MA plot, is a re-scaled and (45 degree) rotated version of a simple two dimensional scatter plot of a vs b where a and b are equal length vectors of positive measurements. This rescaling and rotation allows for better visibility and emphasis of important outliers points that vary between the two measurement conditions.〔Dudoit, S, Yang, YH, Callow, MJ, Speed, TP. (2002). Statistical methods for identifying differentially expressed genes in replicated cDNA microarray experiments. ''Stat. Sin.'' 12:1 111-139〕 Essentially it is a plot of the log ratio () vs the average log () of each pairing of the elements of a and b. Unlike an MA plot, however, because the RA plot takes non-negative integer counts as input, it must employ work-arounds to include mathematically invisible points (such as points where one or both element(s) of the pair is zero). If we modify our original a (or b) vector via: where then R and A can be defined as: R, like M, is plotted on the y-axis and represents a log (fold change) ratio between a and b. A is plotted on the x-axis and represents the average abundance for a coordinate pair. The RA plot provides a quick overview of the distribution and size of a dataset consisting of non-zero counts. 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「RA plot」の詳細全文を読む スポンサード リンク
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