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arXiv 1302.4561math.STstat.TH
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估计多元回归函数最大值位置和大小的最优两阶段方法

Optimal two-stage procedures for estimating location and size of the maximum of a multivariate regression function

Eduard Belitser, Subhashis Ghosal, Harry van Zanten

摘要:

我们提出了一个两阶段的过程估计的位置$\boldsμ$和大小M的最大值的光滑d-变量回归函数f。在第一阶段中,使用从标准非参数平滑方法获得的$\boldsμ$的初步估计。在第二阶段,我们“放大”附近的初步估计,并在附近的一些设计点进行进一步的观察。我们拟合一个适当的多项式回归模型来估计最大值的位置和大小。证明了在适当的光滑性条件和适当的缩放选择下,第二阶段估计比相应的$\boldsμ$和M.更具体地,对于$α$ -平滑回归函数,对于$α>1+\sqrt{1+d/2}$,第一阶段的最优非参数率$n^{-(α-1)/(2α+d)}$和$n^{-α/(2α+d)}$可以分别改进为$n^{-(α-1)/(2α)}$和$n^{-1/2}$。这些速率在所有可能的序贯估计类中是最优的。有趣的是,两阶段的过程解决了“灾难的维数”的问题在一定程度上,作为尺寸d不控制第二阶段的收敛速度,提供了函数类是足够光滑的。我们认为,我们的过程,达到最佳速率的任何平滑水平$α>2$开始与任何幂律率在第一阶段的初步估计的多阶段推广。

英文摘要:

We propose a two-stage procedure for estimating the location $\boldsμ$ and size M of the maximum of a smooth d-variate regression function f. In the first stage, a preliminary estimator of $\boldsμ$ obtained from a standard nonparametric smoothing method is used. At the second stage, we "zoom-in" near the vicinity of the preliminary estimator and make further observations at some design points in that vicinity. We fit an appropriate polynomial regression model to estimate the location and size of the maximum. We establish that, under suitable smoothness conditions and appropriate choice of the zooming, the second stage estimators have better convergence rates than the corresponding first stage estimators of $\boldsμ$ and M. More specifically, for $α$-smooth regression functions, the optimal nonparametric rates $n^{-(α-1)/(2α+d)}$ and $n^{-α/(2α+d)}$ at the first stage can be improved to $n^{-(α-1)/(2α)}$ and $n^{-1/2}$, respectively, for $α>1+\sqrt{1+d/2}$. These rates are optimal in the class of all possible sequential estimators. Interestingly, the two-stage procedure resolves "the curse of the dimensionality" problem to some extent, as the dimension d does not control the second stage convergence rates, provided that the function class is sufficiently smooth. We consider a multi-stage generalization of our procedure that attains the optimal rate for any smoothness level $α>2$ starting with a preliminary estimator with any power-law rate at the first stage.

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