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In statistics, sufficient dimension reduction (SDR) is a paradigm for analyzing data that combines the ideas of dimension reduction with the concept of sufficiency. Dimension reduction has long been a primary goal of regression analysis. Given a response variable ''y'' and a ''p''-dimensional predictor vector , regression analysis aims to study the distribution of , the conditional distribution of given . A dimension reduction is a function that maps to a subset of , ''k'' < ''p'', thereby reducing the dimension of .〔Cook & Adragni (2009) (''Sufficient Dimension Reduction and Prediction in Regression'' ) In: ''Philosophical Transactions of the Royal Society A: Physical, Mathematical and Engineering Sciences'', 367(1906): 4385–4405〕 For example, may be one or more linear combinations of . A dimension reduction is said to be sufficient if the distribution of is the same as that of . In other words, no information about the regression is lost in reducing the dimension of if the reduction is sufficient.〔 == Graphical motivation == In a regression setting, it is often useful to summarize the distribution of graphically. For instance, one may consider a scatter plot of versus one or more of the predictors. A scatter plot that contains all available regression information is called a sufficient summary plot. When is high-dimensional, particularly when , it becomes increasingly challenging to construct and visually interpret sufficiency summary plots without reducing the data. Even three-dimensional scatter plots must be viewed via a computer program, and the third dimension can only be visualized by rotating the coordinate axes. However, if there exists a sufficient dimension reduction with small enough dimension, a sufficient summary plot of versus may be constructed and visually interpreted with relative ease. Hence sufficient dimension reduction allows for graphical intuition about the distribution of , which might not have otherwise been available for high-dimensional data. Most graphical methodology focuses primarily on dimension reduction involving linear combinations of . The rest of this article deals only with such reductions. 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「Sufficient dimension reduction」の詳細全文を読む スポンサード リンク
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