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In statistics, the generalized Dirichlet distribution (GD) is a generalization of the Dirichlet distribution with a more general covariance structure and almost twice the number of parameters. Random variables with a GD distribution are neutral but not completely neutral.〔R. J. Connor and J. E. Mosiman 1969. ''Concepts of independence for proportions with a generalization of the Dirichlet distribution''. Journal of the American Statistical Association, volume 64, pp194--206〕 The density function of is : where we define . Here denotes the Beta function. This reduces to the standard Dirichlet distribution if for ( is arbitrary). For example, if ''k=4'', then the density function of is : where and . Connor and Mosimann define the PDF as they did for the following reason. Define random variables with . Then have the generalized Dirichlet distribution as parametrized above, if the are iid beta with parameters , . == Alternative form given by Wong == Wong 〔T.-T. Wong 1998. ''Generalized Dirichlet distribution in Bayesian analysis''. Applied Mathematics and Computation, volume 97, pp165-181〕 gives the slightly more concise form for : where for and . Note that Wong defines a distribution over a dimensional space (implicitly defining ) while Connor and Mosiman use a dimensional space with . ==General moment function== If , then : where for and . Thus : 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「Generalized Dirichlet distribution」の詳細全文を読む スポンサード リンク
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