Network-based analyses of dynamical systems have become increasingly popular in climate science. Here we address network construction from a statistical perspective and highlight the often ignored fact that the calculated correlation values are only empirical estimates. To measure spurious behaviour as deviation from a ground truth network, we simulate time-dependent isotropic random fields on the sphere and apply common network construction techniques. We find several ways in which the uncertainty stemming from the estimation procedure has major impact on network characteristics. When the data has locally coherent correlation structure, spurious link bundle teleconnections and spurious high-degree clusters have to be expected. Anisotropic estimation variance can also induce severe biases into empirical networks. We validate our findings with ERA5 reanalysis data. Moreover we explain why commonly applied resampling procedures are inappropriate for significance evaluation and propose a statistically more meaningful ensemble construction framework. By communicating which difficulties arise in estimation from scarce data and by presenting which design decisions increase robustness, we hope to contribute to more reliable climate network construction in the future.

在可解释的机器学习中，当地的事后解释算法和固有的可解释模型通常被视为竞争方法。在这项工作中，提供了有关Shapley Values的新颖观点，即Shapley Values，这是一种突出的事后解释技术，并表明它与玻璃盒 - 玻璃盒 - gams密切相关，Glassbox-Gam是一种流行的可解释模型。我们介绍了$ n $ -Shapley值，这是Shapley值的自然扩展，该值解释了具有交互条款的个人预测，直到$ n $。随着$ n $的增加，$ n $ shapley的值会收敛于Shapley-Gam，这是原始功能的独特确定分解。从Shapley-GAM中，我们可以计算出任意秩序的Shapley值，从而确切的见解对这些解释的局限性。然后，我们证明Shapley值恢复了订单$ n $的通用添加剂模型，假设我们允许交互条款在解释中订购$ n $。这意味着原始的Shapley值恢复了玻璃盒煤气。在技​​术端，我们表明，选择值函数的不同方式与原始函数的不同功能分解之间存在一对一的对应关系。这为如何选择值函数的问题提供了一个新的观点。我们还对各种标准分类器中存在的可变相互作用程度进行了经验分析，并讨论了我们结果对算法解释的含义。一个用于计算$ n $ shapley值的Python软件包，并在本文中复制结果，请访问\ url {https://github.com/tml-tuebingen/nshap}。

基于梯度的解释算法何时提供有意义的解释？我们提出了一个必要的标准：它们的特征归因需要与数据歧管的切线空间保持一致。为了提供这一假设的证据，我们介绍了一个基于变异自动编码器的框架，该框架允许估计和生成图像歧管。通过跨各种不同数据集的实验 - MNIST，EMNIST，CIFAR10，X射线肺炎和糖尿病性视网膜病变检测 - 我们证明，功能归因与数据的切线相符，结构化和解释性越多倾向于。特别是，由流行的事后方法（例如集成梯度，SmoothGrad和Input $ \ times $梯度）提供的归因往往比原始梯度更与数据歧管更强烈。结果，我们建议解释算法应积极努力将其解释与数据歧管保持一致。在某种程度上，这可以通过对抗训练来实现，从而可以使所有数据集更好地对齐。必须对模型架构或训练算法进行某种形式的调整，因为我们表明单独的神经网络的概括并不意味着模型梯度与数据歧管的一致性。

在本文中，我们对在表格数据的情况下进行了详尽的理论分析。我们证明，在较大的样本限制中，可以按照算法参数的函数以及与黑框模型相关的一些期望计算来计算表格石灰提供的可解释系数。当要解释的函数具有一些不错的代数结构（根据坐标的子集，线性，乘法或稀疏）时，我们的分析提供了对Lime提供的解释的有趣见解。这些可以应用于一系列机器学习模型，包括高斯内核或卡车随机森林。例如，对于线性函数，我们表明Lime具有理想的属性，可以提供与函数系数成正比的解释，以解释并忽略该函数未使用的坐标来解释。对于基于分区的回归器，另一方面，我们表明石灰会产生可能提供误导性解释的不希望的人工制品。

机器学习通知人类决策者在广泛的任务中的应用。由此产生的问题通常在单个决策者方面配制。我们认为它应该宁愿被描述为一个双人学习问题，其中一个玩家是机器和另一个人。虽然两个玩家都尝试优化最终决定，但设置通常是（1）私人信息的存在和（2）不透明度，即决策者之间的不完美理解。在论文中，我们证明这两个属性都可以复杂化决策。下限量化了最佳地建议的最坏情况的硬度，该决策者是不透明的或可以访问私人信息的决策者。一个上界表明，简单的协调策略几乎最小的最佳。在问题的某些假设下，更高效的学习，例如两个玩家都学会独立采取行动。这种假设是隐含的现有文献中的，例如在机器学习的医学应用中，但理论上尚未被描述或对齐。

Originally, tangles were invented as an abstract tool in mathematical graph theory to prove the famous graph minor theorem. In this paper, we showcase the practical potential of tangles in machine learning applications. Given a collection of cuts of any dataset, tangles aggregate these cuts to point in the direction of a dense structure. As a result, a cluster is softly characterized by a set of consistent pointers. This highly flexible approach can solve clustering problems in various setups, ranging from questionnaires over community detection in graphs to clustering points in metric spaces. The output of our proposed framework is hierarchical and induces the notion of a soft dendrogram, which can help explore the cluster structure of a dataset. The computational complexity of aggregating the cuts is linear in the number of data points. Thus the bottleneck of the tangle approach is to generate the cuts, for which simple and fast algorithms form a sufficient basis. In our paper we construct the algorithmic framework for clustering with tangles, prove theoretical guarantees in various settings, and provide extensive simulations and use cases. Python code is available on github.

In recent years, spectral clustering has become one of the most popular modern clustering algorithms. It is simple to implement, can be solved efficiently by standard linear algebra software, and very often outperforms traditional clustering algorithms such as the k-means algorithm. On the first glance spectral clustering appears slightly mysterious, and it is not obvious to see why it works at all and what it really does. The goal of this tutorial is to give some intuition on those questions. We describe different graph Laplacians and their basic properties, present the most common spectral clustering algorithms, and derive those algorithms from scratch by several different approaches. Advantages and disadvantages of the different spectral clustering algorithms are discussed.

Cybercriminals are moving towards zero-day attacks affecting resource-constrained devices such as single-board computers (SBC). Assuming that perfect security is unrealistic, Moving Target Defense (MTD) is a promising approach to mitigate attacks by dynamically altering target attack surfaces. Still, selecting suitable MTD techniques for zero-day attacks is an open challenge. Reinforcement Learning (RL) could be an effective approach to optimize the MTD selection through trial and error, but the literature fails when i) evaluating the performance of RL and MTD solutions in real-world scenarios, ii) studying whether behavioral fingerprinting is suitable for representing SBC's states, and iii) calculating the consumption of resources in SBC. To improve these limitations, the work at hand proposes an online RL-based framework to learn the correct MTD mechanisms mitigating heterogeneous zero-day attacks in SBC. The framework considers behavioral fingerprinting to represent SBCs' states and RL to learn MTD techniques that mitigate each malicious state. It has been deployed on a real IoT crowdsensing scenario with a Raspberry Pi acting as a spectrum sensor. More in detail, the Raspberry Pi has been infected with different samples of command and control malware, rootkits, and ransomware to later select between four existing MTD techniques. A set of experiments demonstrated the suitability of the framework to learn proper MTD techniques mitigating all attacks (except a harmfulness rootkit) while consuming <1 MB of storage and utilizing <55% CPU and <80% RAM.

Mixtures of von Mises-Fisher distributions can be used to cluster data on the unit hypersphere. This is particularly adapted for high-dimensional directional data such as texts. We propose in this article to estimate a von Mises mixture using a l 1 penalized likelihood. This leads to sparse prototypes that improve clustering interpretability. We introduce an expectation-maximisation (EM) algorithm for this estimation and explore the trade-off between the sparsity term and the likelihood one with a path following algorithm. The model's behaviour is studied on simulated data and, we show the advantages of the approach on real data benchmark. We also introduce a new data set on financial reports and exhibit the benefits of our method for exploratory analysis.

The future of population-based breast cancer screening is likely personalized strategies based on clinically relevant risk models. Mammography-based risk models should remain robust to domain shifts caused by different populations and mammographic devices. Modern risk models do not ensure adaptation across vendor-domains and are often conflated to unintentionally rely on both precursors of cancer and systemic/global mammographic information associated with short- and long-term risk, respectively, which might limit performance. We developed a robust, cross-vendor model for long-term risk assessment. An augmentation-based domain adaption technique, based on flavorization of mammographic views, ensured generalization to an unseen vendor-domain. We trained on samples without diagnosed/potential malignant findings to learn systemic/global breast tissue features, called mammographic texture, indicative of future breast cancer. However, training so may cause erratic convergence. By excluding noise-inducing samples and designing a case-control dataset, a robust ensemble texture model was trained. This model was validated in two independent datasets. In 66,607 Danish women with flavorized Siemens views, the AUC was 0.71 and 0.65 for prediction of interval cancers within two years (ICs) and from two years after screening (LTCs), respectively. In a combination with established risk factors, the model's AUC increased to 0.68 for LTCs. In 25,706 Dutch women with Hologic-processed views, the AUCs were not different from the AUCs in Danish women with flavorized views. The results suggested that the model robustly estimated long-term risk while adapting to an unseen processed vendor-domain. The model identified 8.1% of Danish women accounting for 20.9% of ICs and 14.2% of LTCs.