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arXiv math/0603228math.STstat.TH
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非参数贝叶斯分类

Nonparametric Bayesian Classification

Marc A. Coram

摘要:

贝叶斯方法的分类问题,提出了随机分区发挥核心作用。有人认为,分区的方法有能力利用各种大规模的空间结构,如果它们存在于未知的回归函数$f_0$。一个理想化的一维问题被认为是详细。提出的非参数先验使用随机分裂点将单位区间划分为随机数的片段。发现该先验提供了$Ł^p$拓扑中的回归函数的相合估计,对于任何$1 \leq p < \infty$,以及对于任意可测量的$f_0:[0,1] \to [0,1]$。一个马尔可夫链蒙特卡罗(MCMC)的实现概述和分析。仿真实验表明,所提出的估计与各种传统的估计相比,毫不逊色。后验均值估计和袋装CART估计之间的惊人的相似之处指出和讨论。对于更高的维度,一个广义的先验引入采用随机Voronoi分区的协变量空间。由此产生的估计显示承诺的二维问题,并扩展到任意度量空间与最小的额外的计算工作。

英文摘要:

A Bayesian approach to the classification problem is proposed in which random partitions play a central role. It is argued that the partitioning approach has the capacity to take advantage of a variety of large-scale spatial structures, if they are present in the unknown regression function $f_0$. An idealized one-dimensional problem is considered in detail. The proposed nonparametric prior uses random split points to partition the unit interval into a random number of pieces. This prior is found to provide a consistent estimate of the regression function in the $Ł^p$ topology, for any $1 \leq p < \infty$, and for arbitrary measurable $f_0:[0,1] \to [0,1]$. A Markov chain Monte Carlo (MCMC) implementation is outlined and analyzed. Simulation experiments are conducted to show that the proposed estimate compares favorably with a variety of conventional estimators. A striking resemblance between the posterior mean estimate and the bagged CART estimate is noted and discussed. For higher dimensions, a generalized prior is introduced which employs a random Voronoi partition of the covariate-space. The resulting estimate displays promise on a two-dimensional problem, and extends with a minimum of additional computational effort to arbitrary metric spaces.

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