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arXiv 2007.15421stat.MLcs.LGmath.STstat.MEstat.TH
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相关数据的随机森林

Random Forests for dependent data

Johns Hopkins University(约翰斯·霍普金斯大学);Cornell University(康奈尔大学)

Arkajyoti Saha, Sumanta Basu, Abhirup Datta

摘要:

随机森林(RF)是估计回归函数的最流行的方法之一。当误差为独立同分布时,基于节点内均值和方差的RF算法的局部性质是理想的。对于相关的错误处理,如时间序列和空间设置,其中所有节点中的数据将是相关的,本地操作忽略这种依赖性。此外,RF将涉及相关数据的恢复,违反了自举原则。理论上,已确定i.i.d.的RF一致性。错误,但很少有人知道的情况下,相关的错误。我们提出了RF-GLS,一个新的扩展RF的相关误差过程中,以同样的方式广义最小二乘(GLS)从根本上扩展普通最小二乘(OLS)的线性模型的依赖。这种扩展的关键是将回归树中的局部决策等效表示为全局OLS优化,然后用GLS损失替换以创建GLS风格的回归树。这也协同地解决了恢复问题,因为GLS损失的使用相当于恢复不相关的对比度(预白化数据)而不是相关数据。对于空间设置,RF-GLS可与高斯过程相关误差结合使用,以在新位置生成克里金预测。RF成为具有单位工作协方差阵的RF-GLS的特殊情况。我们建立的RF-GLS下的beta-(绝对正则)混合误差过程的一致性,并表明,这一一般性的结果包括重要的情况下,如自回归时间序列和空间Matern高斯过程。作为一个副产品,我们还建立了一致性的RF β-混合过程,据我们所知,这是第一个这样的结果RF下的依赖。我们的经验表明,RF-GLS的估计和预测下的依赖性比RF实现的改善。

英文摘要:

Random forest (RF) is one of the most popular methods for estimating regression functions. The local nature of the RF algorithm, based on intra-node means and variances, is ideal when errors are i.i.d. For dependent error processes like time series and spatial settings where data in all the nodes will be correlated, operating locally ignores this dependence. Also, RF will involve resampling of correlated data, violating the principles of bootstrap. Theoretically, consistency of RF has been established for i.i.d. errors, but little is known about the case of dependent errors. We propose RF-GLS, a novel extension of RF for dependent error processes in the same way Generalized Least Squares (GLS) fundamentally extends Ordinary Least Squares (OLS) for linear models under dependence. The key to this extension is the equivalent representation of the local decision-making in a regression tree as a global OLS optimization which is then replaced with a GLS loss to create a GLS-style regression tree. This also synergistically addresses the resampling issue, as the use of GLS loss amounts to resampling uncorrelated contrasts (pre-whitened data) instead of the correlated data. For spatial settings, RF-GLS can be used in conjunction with Gaussian Process correlated errors to generate kriging predictions at new locations. RF becomes a special case of RF-GLS with an identity working covariance matrix. We establish consistency of RF-GLS under beta- (absolutely regular) mixing error processes and show that this general result subsumes important cases like autoregressive time series and spatial Matern Gaussian Processes. As a byproduct, we also establish consistency of RF for beta-mixing processes, which to our knowledge, is the first such result for RF under dependence. We empirically demonstrate the improvement achieved by RF-GLS over RF for both estimation and prediction under dependence.

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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