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From Montenegro to northern California, the tech elite dream of building cities where they make the rules. Is this, finally, their moment? The shirtless man in the golden mask and cape has plans to lead his own country one day. There is no location yet, but it will be a crypto-and AI-powered paradise of medical experimentation, filled with people who want to "make death optional," he says. For now, though, he's leading a sparsely attended rave on the second floor of a San Francisco office building. A DJ is spinning at one end of an open room. A handful of people sway and jump on the space cleared out as a dance floor. At a nearby table, coffee is available with many alternative milks.

Summary: This paper proposes a modification of Mondorian Forest which is a variant of Random Forest, a majority vote of decision trees. The authors show that the modified algorithm has the consistency property while the original algorithm does not have one. In particular, when the conditional probability function is Lipschitz, the proposed algorithm achieves the minimax error rate, where the lower bound is previously known. Comments: The technical contribution is to refine the original version of the Mondorian Forest and prove its consistency. The theoretical results are nice and solid. The main idea comes from the original algorithm, thus the originality of the paper is a bit incremental.

Sampling-based model predictive control (MPC) optimization methods, such as Model Predictive Path Integral (MPPI), have recently shown promising results in various robotic tasks. However, it might produce an infeasible trajectory when the distributions of all sampled trajectories are concentrated within high-cost even infeasible regions. In this study, we propose a new method called log-MPPI equipped with a more effective trajectory sampling distribution policy which significantly improves the trajectory feasibility in terms of satisfying system constraints. The key point is to draw the trajectory samples from the normal log-normal (NLN) mixture distribution, rather than from Gaussian distribution. Furthermore, this work presents a method for collision-free navigation in unknown cluttered environments by incorporating the 2D occupancy grid map into the optimization problem of the sampling-based MPC algorithm. We first validate the efficiency and robustness of our proposed control strategy through extensive simulations of 2D autonomous navigation in different types of cluttered environments as well as the cartpole swing-up task. We further demonstrate, through real-world experiments, the applicability of log-MPPI for performing a 2D grid-based collision-free navigation in an unknown cluttered environment, showing its superiority to be utilized with the local costmap without adding additional complexity to the optimization problem. A video demonstrating the real-world and simulation results is available at https://youtu.be/_uGWQEFJSN0.

Climate change has been linked with a widespread decline in the ability of many of the world's forests to bounce back after events such as drought and logging. Forests around the world differ in their resilience to disturbances, but relatively little is know about how that resilience is changing over time. To tease out any shifts, Giovanni Forzieri at the University of Florence, Italy, and his colleagues ran a machine learning algorithm on satellite data of global vegetation from 2000 to 2020 to calculate a metric of resilience. Resilience was defined by a forest's ability to avoid shifting state, such as becoming savannah, and withstand perturbations, such as an influx of insect pests. The researchers found that more than half of forests in arid, tropical and temperate regions – where the majority of the world's trees are found – showed a significant decrease in resilience over the two decades.

XGBoost, short for "Extreme Gradient Boosting," is one of the strongest machine learning algorithms for handling tabular data, a well-deserved reputation due to its success in winning numerous Kaggle competitions. XGBoost is an ensemble machine learning algorithm that usually consists of Decision Trees. The Decision Trees that make up XGBoost are individually referred to as gbtree, short for "gradient boosted tree." The first Decision Tree in the XGBoost ensemble is the base learner whose mistakes all subsequent trees learn from. Although Decision Trees are generally preferred as base learners due to their excellent ensemble scores, in some cases, alternative base learners may outperform them.

The hope of such multivariate analyses is, that the consideration of possible dependencies between the outcomes may lead to procedures with better power (in case of inference) or accuracy (in case of prediction) compared to separate univariate analyses. While the need for the development and use of valid and distributional robust or nonparametric multivariate methods has been recognized and addressed in inferential statistic (Dobler et al., 2020; Friedrich et al., 2019; Konietschke et al., 2015; Smaga, 2017; Vallejo and Ato, 2012; Zimmermann et al., 2020), there do not exist exhausting studies that exploit the potential of multivariate regression methods for prediction. Focussing on tree-based ensemble methods as the Random Forest, it is the aim of this manuscript to close this gap. In particular, we want to answer our research-motivating question: When should a holistic multivariate regression approach be preferred over separate univariate predictions? Corresponding Author Email address: lena.schmid@tu-dortmund.de (Lena Schmid)

Nowadays Machine Learning (ML) techniques are extensively adopted in many socially sensitive systems, thus requiring to carefully study the fairness of the decisions taken by such systems. Many approaches have been proposed to address and to make sure there is no bias against individuals or specific groups which might originally come from biased training datasets or algorithm design. In this regard, we propose a fairness enforcing approach called EiFFFeL:Enforcing Fairness in Forests by Flipping Leaves which exploits tree-based or leaf-based post-processing strategies to relabel leaves of selected decision trees of a given forest. Experimental results show that our approach achieves a user defined group fairness degree without losing a significant amount of accuracy.

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