我们研究了在存在潜在变量存在下从数据重建因果图形模型的问题。感兴趣的主要问题是在潜在变量上恢复因果结构,同时允许一般,可能在变量之间的非线性依赖性。在许多实际问题中,原始观测之间的依赖性(例如,图像中的像素)的依赖性比某些高级潜在特征(例如概念或对象)之间的依赖性要小得多,这是感兴趣的设置。我们提供潜在表示和潜在潜在因果模型的条件可通过减少到混合甲骨文来识别。这些结果突出了学习混合模型的顺序的良好研究问题与观察到和解开的基础结构的问题之间的富裕问题之间的有趣连接。证明是建设性的,并导致几种算法用于明确重建全图形模型。我们讨论高效算法并提供说明实践中算法的实验。
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贝叶斯网络是一组$ N $随机变量的定向非循环图(DAG)(用顶点标识);贝叶斯网络分布(BND)是RV的概率分布,即在图中是马尔可夫的。这种模型的有限混合物是在较大的图表上对这些变量的投影,其具有额外的“隐藏”(或“隐藏”(或“潜伏”)随机变量$ U $,范围在$ \ {1,\ ldots,k \ $,以及从$ U $到其他每个其他顶点的指示边。这种类型的模型是对因因果推理的基础,其中$ U $模型是一种混杂效果。一个非常特殊的案例一直是在理论文学中的长期兴趣:空图。这种分布只是$ k $产品分布的混合。考虑到k $产品分布的混合物的联合分布,以识别产物分布及其混合重量,这一直是长期的问题。我们的结果是:(1)我们改善了从$ \ exp(o(k ^ 2))$到$ \ exp(o(k \ log k)的$ k $产品分布的混合物的示例复杂性(和运行时) )$。鉴于已知的$ \ exp(\ omega(k))$下限,这几乎可以最好。 (2)我们为非空图表提供了第一算法。最大程度为$ \ delta $的图表的复杂性为$ \ exp(o(k(\ delta ^ 2 + \ log k)))$。 (上述复杂性是近似和抑制辅助参数的依赖性。)
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Linear structural causal models (SCMs)-- in which each observed variable is generated by a subset of the other observed variables as well as a subset of the exogenous sources-- are pervasive in causal inference and casual discovery. However, for the task of causal discovery, existing work almost exclusively focus on the submodel where each observed variable is associated with a distinct source with non-zero variance. This results in the restriction that no observed variable can deterministically depend on other observed variables or latent confounders. In this paper, we extend the results on structure learning by focusing on a subclass of linear SCMs which do not have this property, i.e., models in which observed variables can be causally affected by any subset of the sources, and are allowed to be a deterministic function of other observed variables or latent confounders. This allows for a more realistic modeling of influence or information propagation in systems. We focus on the task of causal discovery form observational data generated from a member of this subclass. We derive a set of necessary and sufficient conditions for unique identifiability of the causal structure. To the best of our knowledge, this is the first work that gives identifiability results for causal discovery under both latent confounding and deterministic relationships. Further, we propose an algorithm for recovering the underlying causal structure when the aforementioned conditions are satisfied. We validate our theoretical results both on synthetic and real datasets.
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常用图是表示和可视化因果关系的。对于少量变量,这种方法提供了简洁和清晰的方案的视图。随着下属的变量数量增加,图形方法可能变得不切实际,并且表示的清晰度丢失。变量的聚类是减少因果图大小的自然方式,但如果任意实施,可能会错误地改变因果关系的基本属性。我们定义了一种特定类型的群集,称为Transit Cluster,保证在某些条件下保留因果效应的可识别性属性。我们提供了一种用于在给定图中查找所有传输群集的声音和完整的算法,并演示集群如何简化因果效应的识别。我们还研究了逆问题,其中一个人以群集的图形开始,寻找扩展图,其中因果效应的可识别性属性保持不变。我们表明这种结构稳健性与过境集群密切相关。
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我们分析了在没有特定分布假设的常规设置中从观察数据的学习中学循环图形模型的复杂性。我们的方法是信息定理,并使用本地马尔可夫边界搜索程序,以便在基础图形模型中递归地构建祖先集。也许令人惊讶的是,我们表明,对于某些图形集合,一个简单的前向贪婪搜索算法(即没有向后修剪阶段)足以学习每个节点的马尔可夫边界。这显着提高了我们在节点的数量中显示的样本复杂性。然后应用这一点以在从文献中概括存在现有条件的新型标识性条件下学习整个图。作为独立利益的问题,我们建立了有限样本的保障,以解决从数据中恢复马尔可夫边界的问题。此外,我们将我们的结果应用于特殊情况的Polytrees,其中假设简化,并提供了多项识别的明确条件,并且在多项式时间中可以识别和可知。我们进一步说明了算法在仿真研究中易于实现的算法的性能。我们的方法是普遍的,用于无需分布假设的离散或连续分布,并且由于这种棚灯对有效地学习来自数据的定向图形模型结构所需的最小假设。
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我们证明了(a)具有通用近似功能的广泛的深层变量模型的可识别性,并且(b)是通常在实践中使用的变异自动编码器的解码器。与现有工作不同,我们的分析不需要弱监督,辅助信息或潜在空间中的条件。最近,研究了此类模型的可识别性。在这些作品中,主要的假设是,还可以观察到辅助变量$ u $(也称为侧面信息)。同时,几项作品从经验上观察到,这在实践中似乎并不是必需的。在这项工作中,我们通过证明具有通用近似功能的广泛生成(即无监督的)模型来解释这种行为,无需侧面信息$ u $:我们证明了整个生成模型的可识别性$ u $,仅观察数据$ x $。我们考虑的模型与实践中使用的自动编码器体系结构紧密连接,该体系结构利用了潜在空间中的混合先验和编码器中的Relu/Leaky-Relu激活。我们的主要结果是可识别性层次结构,该层次结构显着概括了先前的工作,并揭示了不同的假设如何导致可识别性的“优势”不同。例如,我们最薄弱的结果确定了(无监督的)可识别性,直到仿射转换已经改善了现有工作。众所周知,这些模型具有通用近似功能,而且它们已被广泛用于实践中来学习数据表示。
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人们对利用置换推理来搜索定向的无环因果模型的方法越来越兴趣,包括Teysier和Kohler和Solus,Wang和Uhler的GSP的“订购搜索”。我们通过基于置换的操作Tuck扩展了后者的方法,并开发了一类算法,即掌握,这些算法在越来越弱的假设下比忠诚度更有效且方向保持一致。最放松的掌握形式优于模拟中许多最新的因果搜索算法,即使对于具有超过100个变量的密集图和图形,也可以有效,准确地搜索。
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也称为(非参数)结构方程模型(SEMS)的结构因果模型(SCM)被广泛用于因果建模目的。特别是,也称为递归SEM的无循环SCMS,形成了一个研究的SCM的良好的子类,概括了因果贝叶斯网络来允许潜在混淆。在本文中,我们调查了更多普通环境中的SCM,允许存在潜在混杂器和周期。我们展示在存在周期中,无循环SCM的许多方便的性质通常不会持有:它们并不总是有解决方案;它们并不总是诱导独特的观察,介入和反事实分布;边缘化并不总是存在,如果存在边缘模型并不总是尊重潜在的投影;他们并不总是满足马尔可夫财产;他们的图表并不总是与他们的因果语义一致。我们证明,对于SCM一般,这些属性中的每一个都在某些可加工条件下保持。我们的工作概括了SCM的结果,迄今为止仅针对某些特殊情况所知的周期。我们介绍了将循环循环设置扩展到循环设置的简单SCM的类,同时保留了许多方便的无环SCM的性能。用本文,我们的目标是为SCM提供统计因果建模的一般理论的基础。
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We study experiment design for unique identification of the causal graph of a system where the graph may contain cycles. The presence of cycles in the structure introduces major challenges for experiment design as, unlike acyclic graphs, learning the skeleton of causal graphs with cycles may not be possible from merely the observational distribution. Furthermore, intervening on a variable in such graphs does not necessarily lead to orienting all the edges incident to it. In this paper, we propose an experiment design approach that can learn both cyclic and acyclic graphs and hence, unifies the task of experiment design for both types of graphs. We provide a lower bound on the number of experiments required to guarantee the unique identification of the causal graph in the worst case, showing that the proposed approach is order-optimal in terms of the number of experiments up to an additive logarithmic term. Moreover, we extend our result to the setting where the size of each experiment is bounded by a constant. For this case, we show that our approach is optimal in terms of the size of the largest experiment required for uniquely identifying the causal graph in the worst case.
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In this review, we discuss approaches for learning causal structure from data, also called causal discovery. In particular, we focus on approaches for learning directed acyclic graphs (DAGs) and various generalizations which allow for some variables to be unobserved in the available data. We devote special attention to two fundamental combinatorial aspects of causal structure learning. First, we discuss the structure of the search space over causal graphs. Second, we discuss the structure of equivalence classes over causal graphs, i.e., sets of graphs which represent what can be learned from observational data alone, and how these equivalence classes can be refined by adding interventional data.
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我们介绍并研究了分布的邻居晶格分解,这是有条件独立性的紧凑,非图形表示,在没有忠实的图形表示的情况下是有效的。这个想法是将变量的一组社区视为子集晶格,并将此晶格分配到凸sublattices中,每个晶格都直接编码有条件的独立关系集合。我们表明,这种分解存在于任何组成型绘画中,并且可以在高维度中有效且一致地计算出来。 {特别是,这给了一种方法来编码满足组合公理的分布所隐含的所有独立关系,该分布严格比图形方法通常假定的忠实假设弱弱。}我们还讨论了各种特殊案例,例如图形模型和投影晶格,每个晶格都有直观的解释。一路上,我们看到了这个问题与邻域回归密切相关的,该回归已在图形模型和结构方程式的背景下进行了广泛的研究。
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In this paper we prove the so-called "Meek Conjecture". In particular, we show that if a DAG H is an independence map of another DAG G, then there exists a finite sequence of edge additions and covered edge reversals in G such that (1) after each edge modification H remains an independence map of G and ( 2) after all modifications G = H. As shown by Meek (1997), this result has an important consequence for Bayesian approaches to learning Bayesian networks from data: in the limit of large sample size, there exists a twophase greedy search algorithm that-when applied to a particular sparsely-connected search space-provably identifies a perfect map of the generative distribution if that perfect map is a DAG. We provide a new implementation of the search space, using equivalence classes as states, for which all operators used in the greedy search can be scored efficiently using local functions of the nodes in the domain. Finally, using both synthetic and real-world datasets, we demonstrate that the two-phase greedy approach leads to good solutions when learning with finite sample sizes.
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Learning causal structure from observational data often assumes that we observe independent and identically distributed (i.\,i.\,d) data. The traditional approach aims to find a graphical representation that encodes the same set of conditional independence relationships as those present in the observed distribution. It is known that under i.\,i.\,d assumption, even with infinite data, there is a limit to how fine-grained a causal structure we can identify. To overcome this limitation, recent work has explored using data originating from different, related environments to learn richer causal structure. These approaches implicitly rely on the independent causal mechanisms (ICM) principle, which postulates that the mechanism giving rise to an effect given its causes and the mechanism which generates the causes do not inform or influence each other. Thus, components of the causal model can independently change from environment to environment. Despite its wide application in machine learning and causal inference, there is a lack of statistical formalization of the ICM principle and how it enables identification of richer causal structures from grouped data. Here we present new causal de Finetti theorems which offer a first statistical formalization of ICM principle and show how causal structure identification is possible from exchangeable data. Our work provides theoretical justification for a broad range of techniques leveraging multi-environment data to learn causal structure.
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We consider the problem of recovering the causal structure underlying observations from different experimental conditions when the targets of the interventions in each experiment are unknown. We assume a linear structural causal model with additive Gaussian noise and consider interventions that perturb their targets while maintaining the causal relationships in the system. Different models may entail the same distributions, offering competing causal explanations for the given observations. We fully characterize this equivalence class and offer identifiability results, which we use to derive a greedy algorithm called GnIES to recover the equivalence class of the data-generating model without knowledge of the intervention targets. In addition, we develop a novel procedure to generate semi-synthetic data sets with known causal ground truth but distributions closely resembling those of a real data set of choice. We leverage this procedure and evaluate the performance of GnIES on synthetic, real, and semi-synthetic data sets. Despite the strong Gaussian distributional assumption, GnIES is robust to an array of model violations and competitive in recovering the causal structure in small- to large-sample settings. We provide, in the Python packages "gnies" and "sempler", implementations of GnIES and our semi-synthetic data generation procedure.
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Causal disentanglement seeks a representation of data involving latent variables that relate to one another via a causal model. A representation is identifiable if both the latent model and the transformation from latent to observed variables are unique. In this paper, we study observed variables that are a linear transformation of a linear latent causal model. Data from interventions are necessary for identifiability: if one latent variable is missing an intervention, we show that there exist distinct models that cannot be distinguished. Conversely, we show that a single intervention on each latent variable is sufficient for identifiability. Our proof uses a generalization of the RQ decomposition of a matrix that replaces the usual orthogonal and upper triangular conditions with analogues depending on a partial order on the rows of the matrix, with partial order determined by a latent causal model. We corroborate our theoretical results with a method for causal disentanglement that accurately recovers a latent causal model.
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我们考虑代表代理模型的问题,该模型使用我们称之为CSTREES的阶段树模型的适当子类对离散数据编码离散数据的原因模型。我们表明,可以通过集合表达CSTREE编码的上下文专用信息。由于并非所有阶段树模型都承认此属性,CSTREES是一个子类,可提供特定于上下文的因果信息的透明,直观和紧凑的表示。我们证明了CSTREEES承认全球性马尔可夫属性,它产生了模型等价的图形标准,概括了Verma和珍珠的DAG模型。这些结果延伸到一般介入模型设置,使CSTREES第一族的上下文专用模型允许介入模型等价的特征。我们还为CSTREE的最大似然估计器提供了一种封闭式公式,并使用它来表示贝叶斯信息标准是该模型类的本地一致的分数函数。在模拟和实际数据上分析了CSTHEELE的性能,在那里我们看到与CSTREELE而不是一般上演树的建模不会导致预测精度的显着损失,同时提供了特定于上下文的因果信息的DAG表示。
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我们考虑从数据学习树结构ising模型的问题,使得使用模型计算的后续预测是准确的。具体而言,我们的目标是学习一个模型,使得小组变量$ S $的后海报$ p(x_i | x_s)$。自推出超过50年以来,有效计算最大似然树的Chow-Liu算法一直是学习树结构图形模型的基准算法。 [BK19]示出了关于以预测的局部总变化损耗的CHOW-LIU算法的样本复杂性的界限。虽然这些结果表明,即使在恢复真正的基础图中也可以学习有用的模型是不可能的,它们的绑定取决于相互作用的最大强度,因此不会达到信息理论的最佳选择。在本文中,我们介绍了一种新的算法,仔细结合了Chow-Liu算法的元素,以便在预测的损失下有效地和最佳地学习树ising模型。我们的算法对模型拼写和对抗损坏具有鲁棒性。相比之下,我们表明庆祝的Chow-Liu算法可以任意次优。
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We focus on causal discovery in the presence of measurement error in linear systems where the mixing matrix, i.e., the matrix indicating the independent exogenous noise terms pertaining to the observed variables, is identified up to permutation and scaling of the columns. We demonstrate a somewhat surprising connection between this problem and causal discovery in the presence of unobserved parentless causes, in the sense that there is a mapping, given by the mixing matrix, between the underlying models to be inferred in these problems. Consequently, any identifiability result based on the mixing matrix for one model translates to an identifiability result for the other model. We characterize to what extent the causal models can be identified under a two-part faithfulness assumption. Under only the first part of the assumption (corresponding to the conventional definition of faithfulness), the structure can be learned up to the causal ordering among an ordered grouping of the variables but not all the edges across the groups can be identified. We further show that if both parts of the faithfulness assumption are imposed, the structure can be learned up to a more refined ordered grouping. As a result of this refinement, for the latent variable model with unobserved parentless causes, the structure can be identified. Based on our theoretical results, we propose causal structure learning methods for both models, and evaluate their performance on synthetic data.
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我们研究在有关系统的结构侧信息时学习一组变量的贝叶斯网络(BN)的问题。众所周知,学习一般BN的结构在计算上和统计上具有挑战性。然而,通常在许多应用中,关于底层结构的侧面信息可能会降低学习复杂性。在本文中,我们开发了一种基于递归约束的算法,其有效地将这些知识(即侧信息)纳入学习过程。特别地,我们研究了关于底层BN的两种类型的结构侧信息:(i)其集团数的上限是已知的,或者(ii)它是无菱形的。我们为学习算法提供理论保证,包括每个场景所需的最坏情况的测试数量。由于我们的工作,我们表明可以通过多项式复杂性学习有界树木宽度BNS。此外,我们评估了综合性和现实世界结构的算法的性能和可扩展性,并表明它们优于最先进的结构学习算法。
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因果推断的一个共同主题是学习观察到的变量(也称为因果发现)之间的因果关系。考虑到大量候选因果图和搜索空间的组合性质,这通常是一项艰巨的任务。也许出于这个原因,到目前为止,大多数研究都集中在相对较小的因果图上,并具有多达数百个节点。但是,诸如生物学之类的领域的最新进展使生成实验数据集,并进行了数千种干预措施,然后进行了数千个变量的丰富分析,从而增加了机会和迫切需要大量因果图模型。在这里,我们介绍了因子定向无环图(F-DAG)的概念,是将搜索空间限制为非线性低级别因果相互作用模型的一种方法。将这种新颖的结构假设与最近的进步相结合,弥合因果发现与连续优化之间的差距,我们在数千个变量上实现了因果发现。此外,作为统计噪声对此估计程序的影响的模型,我们根据随机图研究了F-DAG骨架的边缘扰动模型,并量化了此类扰动对F-DAG等级的影响。该理论分析表明,一组候选F-DAG比整个DAG空间小得多,因此在很难评估基础骨架的高维度中更统计学上的稳定性。我们提出了因子图(DCD-FG)的可区分因果发现,这是对高维介入数据的F-DAG约束因果发现的可扩展实现。 DCD-FG使用高斯非线性低级结构方程模型,并且在模拟中的最新方法以及最新的大型单细胞RNA测序数据集中,与最新方法相比显示出显着改善遗传干预措施。
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