arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 1707.09161cs.ITmath.ITmath.STstat.MLstat.TH
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高维稀疏向量的经验Bayes估计

Empirical Bayes Estimators for High-Dimensional Sparse Vectors

Pavan Srinath, Ramji Venkataramanan

摘要:

研究了由独立同分布的观测值估计高维稀疏向量$\boldsymbolθ \in \mathbb{R}^n$的问题。考虑高斯噪声。使用平方误差损失来测量性能。经验贝叶斯收缩估计,使用伯努利-高斯先验,进行了分析和比较,与著名的软阈值估计。我们得到了Stein无偏风险估计和两个估计的损失函数的浓度不等式。结果表明,对于大的$n$,风险估计和损失函数都集中在接近真实风险的确定性值上。取决于底层的$\boldsymbolθ$,所提出的经验贝叶斯(eBayes)估计器或软阈值化可以具有较小的损失。我们考虑一个混合估计,试图选择更好的软阈值估计和eBayes估计通过比较他们的风险估计。结果表明:i)混合估计量的损失集中在两个竞争估计量的损失的最小值上,以及ii)混合估计量的风险在两个风险的最小值的$\frac{1}{\sqrt{n}}$阶内。仿真结果支持理论结果。最后,我们使用eBayes和混合估计器作为压缩感知近似消息传递(AMP)算法中的去噪器,并表明它们的性能在很宽的设置范围内优于软阈值去噪器。

英文摘要:

The problem of estimating a high-dimensional sparse vector $\boldsymbolθ \in \mathbb{R}^n$ from an observation in i.i.d. Gaussian noise is considered. The performance is measured using squared-error loss. An empirical Bayes shrinkage estimator, derived using a Bernoulli-Gaussian prior, is analyzed and compared with the well-known soft-thresholding estimator. We obtain concentration inequalities for the Stein's unbiased risk estimate and the loss function of both estimators. The results show that for large $n$, both the risk estimate and the loss function concentrate on deterministic values close to the true risk. Depending on the underlying $\boldsymbolθ$, either the proposed empirical Bayes (eBayes) estimator or soft-thresholding may have smaller loss. We consider a hybrid estimator that attempts to pick the better of the soft-thresholding estimator and the eBayes estimator by comparing their risk estimates. It is shown that: i) the loss of the hybrid estimator concentrates on the minimum of the losses of the two competing estimators, and ii) the risk of the hybrid estimator is within order $\frac{1}{\sqrt{n}}$ of the minimum of the two risks. Simulation results are provided to support the theoretical results. Finally, we use the eBayes and hybrid estimators as denoisers in the approximate message passing (AMP) algorithm for compressed sensing, and show that their performance is superior to the soft-thresholding denoiser in a wide range of settings.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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