我们开发了一个框架,用于在线环境中使用有效的覆盖范围保证构建不确定性集,其中基础数据分布可以急剧(甚至对手)随着时间的推移而发生巨大变化。我们提出的技术非常灵活,因为它可以与任何在线学习算法集成,需要最低限度的实施工作和计算成本。我们方法比现有替代方案的关键优势(也基于共形推断)是我们不需要将数据分为培训和保持校准集。这使我们能够以完全在线的方式拟合预测模型,并利用最新的观察结果来构建校准的不确定性集。因此,与现有技术相反,(i)我们构建的集合可以迅速适应分布的新变化; (ii)我们的过程不需要在每个时间步骤进行改装。使用合成和现实世界的基准数据集,我们证明了理论的有效性以及提案对现有技术的提高绩效。为了证明所提出的方法的更大灵活性,我们展示了如何为多出输出回归问题构造有效的间隔,而以前的顺序校准方法由于不切实际的计算和内存需求而无法处理。
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We develop a method to generate predictive regions that cover a multivariate response variable with a user-specified probability. Our work is composed of two components. First, we use a deep generative model to learn a representation of the response that has a unimodal distribution. Existing multiple-output quantile regression approaches are effective in such cases, so we apply them on the learned representation, and then transform the solution to the original space of the response. This process results in a flexible and informative region that can have an arbitrary shape, a property that existing methods lack. Second, we propose an extension of conformal prediction to the multivariate response setting that modifies any method to return sets with a pre-specified coverage level. The desired coverage is theoretically guaranteed in the finite-sample case for any distribution. Experiments conducted on both real and synthetic data show that our method constructs regions that are significantly smaller compared to existing techniques.
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现在通常用于高风险设置,如医疗诊断,如医疗诊断,那么需要不确定量化,以避免后续模型失败。无分发的不确定性量化(无分布UQ)是用户友好的范式,用于为这种预测创建统计上严格的置信区间/集合。批判性地,间隔/集合有效而不进行分布假设或模型假设,即使具有最多许多DataPoints也具有显式保证。此外,它们适应输入的难度;当输入示例很困难时,不确定性间隔/集很大,信号传达模型可能是错误的。在没有多大的工作和没有再培训的情况下,可以在任何潜在的算法(例如神经网络)上使用无分​​发方法,以产生置信度集,以便包含用户指定概率,例如90%。实际上,这些方法易于理解和一般,应用于计算机视觉,自然语言处理,深度加强学习等领域出现的许多现代预测问题。这种实践介绍是针对对无需统计学家的免费UQ的实际实施感兴趣的读者。我们通过实际的理论和无分发UQ的应用领导读者,从保形预测开始,并使无关的任何风险的分布控制,如虚假发现率,假阳性分布检测,等等。我们将包括Python中的许多解释性插图,示例和代码样本,具有Pytorch语法。目标是提供读者对无分配UQ的工作理解,使它们能够将置信间隔放在算法上,其中包含一个自包含的文档。
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Model-X条件随机测试是有条件独立性测试的通用框架,解锁了新的可能性,以发现与感兴趣的响应有条件相关的特征,同时控制I型错误率。该测试的一个吸引力的优势是,它可以与任何机器学习模型一起使用来设计强大的测试统计数据。反过来,Model-X文献中的常见实践是使用机器学习模型形成测试统计量,经过培训,以最大程度地提高预测精度,希望能够获得良好的功率测试。但是,这里的理想目标是推动模型(在训练期间)以最大程度地提高测试功能,而不仅仅是预测精度。在本文中,我们通过首次引入新型模型拟合方案来弥合这一差距,这些方案旨在明确提高Model-X测试的功能。这是通过引入新的成本函数来完成的,该功能旨在最大化用于衡量有条件独立性违反的测试统计量。使用合成和真实的数据集,我们证明了我们提出的损失函数与各种基本预测模型(Lasso,弹性网和深神经网络)的组合始终增加所获得的正确发现的数量,同时维持I型错误率下的I型错误率控制。
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机器学习方法越来越广泛地用于医疗保健,运输和金融等高危环境中。在这些环境中,重要的是,模型要产生校准的不确定性以反映其自信并避免失败。在本文中,我们调查了有关深度学习的不确定性定量(UQ)的最新著作,特别是针对其数学属性和广泛适用性的无分配保形方法。我们将涵盖共形方法的理论保证,引入在时空数据的背景下提高UQ的校准和效率的技术,并讨论UQ在安全决策中的作用。
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A flexible method is developed to construct a confidence interval for the frequency of a queried object in a very large data set, based on a much smaller sketch of the data. The approach requires no knowledge of the data distribution or of the details of the sketching algorithm; instead, it constructs provably valid frequentist confidence intervals for random queries using a conformal inference approach. After achieving marginal coverage for random queries under the assumption of data exchangeability, the proposed method is extended to provide stronger inferences accounting for possibly heterogeneous frequencies of different random queries, redundant queries, and distribution shifts. While the presented methods are broadly applicable, this paper focuses on use cases involving the count-min sketch algorithm and a non-linear variation thereof, to facilitate comparison to prior work. In particular, the developed methods are compared empirically to frequentist and Bayesian alternatives, through simulations and experiments with data sets of SARS-CoV-2 DNA sequences and classic English literature.
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在过去几十年中,已经提出了各种方法,用于估计回归设置中的预测间隔,包括贝叶斯方法,集合方法,直接间隔估计方法和保形预测方法。重要问题是这些方法的校准:生成的预测间隔应该具有预定义的覆盖水平,而不会过于保守。在这项工作中,我们从概念和实验的角度审查上述四类方法。结果来自各个域的基准数据集突出显示从一个数据集中的性能的大波动。这些观察可能归因于违反某些类别的某些方法所固有的某些假设。我们说明了如何将共形预测用作提供不具有校准步骤的方法的方法的一般校准程序。
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The main objective of Prognostics and Health Management is to estimate the Remaining Useful Lifetime (RUL), namely, the time that a system or a piece of equipment is still in working order before starting to function incorrectly. In recent years, numerous machine learning algorithms have been proposed for RUL estimation, mainly focusing on providing more accurate RUL predictions. However, there are many sources of uncertainty in the problem, such as inherent randomness of systems failure, lack of knowledge regarding their future states, and inaccuracy of the underlying predictive models, making it infeasible to predict the RULs precisely. Hence, it is of utmost importance to quantify the uncertainty alongside the RUL predictions. In this work, we investigate the conformal prediction (CP) framework that represents uncertainty by predicting sets of possible values for the target variable (intervals in the case of RUL) instead of making point predictions. Under very mild technical assumptions, CP formally guarantees that the actual value (true RUL) is covered by the predicted set with a degree of certainty that can be prespecified. We study three CP algorithms to conformalize any single-point RUL predictor and turn it into a valid interval predictor. Finally, we conformalize two single-point RUL predictors, deep convolutional neural networks and gradient boosting, and illustrate their performance on the Commercial Modular Aero-Propulsion System Simulation (C-MAPSS) data sets.
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We present a new distribution-free conformal prediction algorithm for sequential data (e.g., time series), called the \textit{sequential predictive conformal inference} (\texttt{SPCI}). We specifically account for the nature that the time series data are non-exchangeable, and thus many existing conformal prediction algorithms based on temporal residuals are not applicable. The main idea is to exploit the temporal dependence of conformity scores; thus, the past conformity scores contain information about future ones. Then we cast the problem of conformal prediction interval as predicting the quantile of a future residual, given a prediction algorithm. Theoretically, we establish asymptotic valid conditional coverage upon extending consistency analyses in quantile regression. Using simulation and real-data experiments, we demonstrate a significant reduction in interval width of \texttt{SPCI} compared to other existing methods under the desired empirical coverage.
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Accurate uncertainty measurement is a key step to building robust and reliable machine learning systems. Conformal prediction is a distribution-free uncertainty quantification algorithm popular for its ease of implementation, statistical coverage guarantees, and versatility for underlying forecasters. However, existing conformal prediction algorithms for time series are limited to single-step prediction without considering the temporal dependency. In this paper we propose a Copula Conformal Prediction algorithm for multivariate, multi-step Time Series forecasting, CopulaCPTS. On several synthetic and real-world multivariate time series datasets, we show that CopulaCPTS produces more calibrated and sharp confidence intervals for multi-step prediction tasks than existing techniques.
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共形推断是一种灵活的方法,用于将任何黑框模型(例如神经网,随机森林)的预测转换为有效的预测集。唯一必要的假设是可以交换培训和测试数据(例如I.I.D.)。不幸的是,这种假设通常在在线环境中是不现实的,在线环境中,生成数据的处理可能会随着时间而变化,并且连续数据点通常在时间上相关。在本文中,我们开发了一种在线算法,用于生成对这些偏差的预测间隔。我们的方法基于共形推断,因此可以与任何黑盒预测因子结合使用。我们表明,我们算法的覆盖误差受环境中基础变化的大小控制,因此直接将分布移位的大小与预测问题的难度联系起来。最后,我们将过程应用于两个现实世界的设置,发现我们的方法在现实世界动态下产生了强大的预测间隔。
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在这项工作中,我们对基本思想和新颖的发展进行了综述的综述,这是基于最小的假设的一种无创新的,无分配的,非参数预测的方法 - 能够以非常简单的方式预测集屈服在有限样本案例中,在统计意义上也有效。论文中提供的深入讨论涵盖了共形预测的理论基础,然后继续列出原始想法的更高级的发展和改编。
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必须校准不确定性估计值(即准确)和清晰(即信息性),以便有用。这激发了各种重新校准的方法,这些方法使用固定数据将未校准的模型转化为校准模型。但是,由于原始模型也是概率模型,因此现有方法的适用性受到限制。我们在回归中引入了一种用于重新校准的算法类别,我们称为模块化保形校准(MCC)。该框架允许人们将任何回归模型转换为校准的概率模型。 MCC的模块化设计使我们能够对现有算法进行简单调整,以实现良好的分配预测。我们还为MCC算法提供有限样本的校准保证。我们的框架恢复了等渗的重新校准,保形校准和共形间隔预测,这意味着我们的理论结果也适用于这些方法。最后,我们对17个回归数据集进行了MCC的经验研究。我们的结果表明,在我们的框架中设计的新算法实现了接近完美的校准,并相对于现有方法提高了清晰度。
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We develop a general framework for distribution-free predictive inference in regression, using conformal inference. The proposed methodology allows for the construction of a prediction band for the response variable using any estimator of the regression function. The resulting prediction band preserves the consistency properties of the original estimator under standard assumptions, while guaranteeing finite-sample marginal coverage even when these assumptions do not hold. We analyze and compare, both empirically and theoretically, the two major variants of our conformal framework: full conformal inference and split conformal inference, along with a related jackknife method. These methods offer different tradeoffs between statistical accuracy (length of resulting prediction intervals) and computational efficiency. As extensions, we develop a method for constructing valid in-sample prediction intervals called rank-one-out conformal inference, which has essentially the same computational efficiency as split conformal inference. We also describe an extension of our procedures for producing prediction bands with locally varying length, in order to adapt to heteroskedascity in the data. Finally, we propose a model-free notion of variable importance, called leave-one-covariate-out or LOCO inference. Accompanying this paper is an R package conformalInference that implements all of the proposals we have introduced. In the spirit of reproducibility, all of our empirical results can also be easily (re)generated using this package.
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A flexible conformal inference method is developed to construct confidence intervals for the frequencies of queried objects in very large data sets, based on a much smaller sketch of those data. The approach is data-adaptive and requires no knowledge of the data distribution or of the details of the sketching algorithm; instead, it constructs provably valid frequentist confidence intervals under the sole assumption of data exchangeability. Although our solution is broadly applicable, this paper focuses on applications involving the count-min sketch algorithm and a non-linear variation thereof. The performance is compared to that of frequentist and Bayesian alternatives through simulations and experiments with data sets of SARS-CoV-2 DNA sequences and classic English literature.
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我们研究保形预测的鲁棒性,这是标记噪声的不确定性定量的强大工具。我们的分析解决了回归和分类问题,表征了何时以及如何构建正确覆盖未观察到的无噪音地面真相标签的不确定性集。通过风格化的理论示例和实际实验,我们认为天真的保形预测涵盖了无噪声的地面真相标签,除非噪声分布是对手设计的。这使我们相信,除了病理数据分布或噪声源外,对标签噪声的纠正是不必要的。在这种情况下,我们还可以在保形预测算法中校正有界大小的噪声,以确保在没有得分或数据规律性的情况下正确覆盖地面真相标签。
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本文开发了新型的保形方法,以测试是否从与参考集相同的分布中采样了新的观察结果。以创新的方式将感应性和偏置的共形推断融合,所描述的方法可以以原则性的方式基于已知的分布式数据的依赖侧信息重新权重标准p值,并且可以自动利用最强大的优势来自任何一级和二进制分类器的模型。该解决方案可以通过样品分裂或通过新颖的转置交叉验证+方案来实现,该方案与现有的交叉验证方法相比,由于更严格的保证,这也可能在共形推理的其他应用中有用。在研究错误的发现率控制和在具有几个可能的离群值的多个测试框架内的虚假发现率控制和功率之后,提出的解决方案被证明通过模拟以及用于图像识别和表格数据的应用超过了标准的共形P值。
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分位数回归是统计学习中的一个基本问题,这是由于需要量化预测中的不确定性或对多样化的人群建模而不过分减少的统计学习。例如,流行病学预测,成本估算和收入预测都可以准确地量化可能的值的范围。因此,在计量经济学,统计和机器学习的多年研究中,已经为这个问题开发了许多模型。而不是提出另一种(新的)算法用于分位数回归,而是采用元观点:我们研究用于汇总任意数量的有条件分位模型的方法,以提高准确性和鲁棒性。我们考虑加权合奏,其中权重不仅可能因单个模型,而且要多于分位数和特征值而变化。我们在本文中考虑的所有模型都可以使用现代深度学习工具包适合,因此可以广泛访问(从实现的角度)和可扩展。为了提高预测分位数的准确性(或等效地,预测间隔),我们开发了确保分位数保持单调排序的工具,并采用保形校准方法。可以使用这些,而无需对原始模型的原始库进行任何修改。我们还回顾了一些围绕分数聚集和相关评分规则的基本理论,并为该文献做出了一些新的结果(例如,在分类或等渗后回归只能提高加权间隔得分的事实)。最后,我们提供了来自两个不同基准存储库的34个数据集的广泛的经验比较套件。
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有效的决策需要了解预测中固有的不确定性。在回归中,这种不确定性可以通过各种方法估算;然而,许多这些方法对调谐进行费力,产生过度自确性的不确定性间隔,或缺乏敏锐度(给予不精确的间隔)。我们通过提出一种通过定义具有两个不同损失功能的神经网络来捕获回归中的预测分布的新方法来解决这些挑战。具体地,一个网络近似于累积分布函数,第二网络近似于其逆。我们将此方法称为合作网络(CN)。理论分析表明,优化的固定点处于理想化的解决方案,并且该方法是渐近的与地面真理分布一致。凭经验,学习是简单且强大的。我们基准CN对两个合成和六个现实世界数据集的几种常见方法,包括预测来自电子健康记录的糖尿病患者的A1C值,其中不确定是至关重要的。在合成数据中,所提出的方法与基本上匹配地面真理。在真实世界数据集中,CN提高了许多性能度量的结果,包括对数似然估计,平均误差,覆盖估计和预测间隔宽度。
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Deep neural networks are powerful tools to detect hidden patterns in data and leverage them to make predictions, but they are not designed to understand uncertainty and estimate reliable probabilities. In particular, they tend to be overconfident. We begin to address this problem in the context of multi-class classification by developing a novel training algorithm producing models with more dependable uncertainty estimates, without sacrificing predictive power. The idea is to mitigate overconfidence by minimizing a loss function, inspired by advances in conformal inference, that quantifies model uncertainty by carefully leveraging hold-out data. Experiments with synthetic and real data demonstrate this method can lead to smaller conformal prediction sets with higher conditional coverage, after exact calibration with hold-out data, compared to state-of-the-art alternatives.
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