Ensemble Learning
Generalized XGBoost Method
This method has achieved excellent predictive performance in many fields and has exhibited many advantages, and is consequently considered especially suitable for the statistical analysis of big data. However, this method is limited because its loss function must be convex. For many scenario-specific problems, such as non-life insurance pricing, the distribution of predictor variables is often heavytailed, so the optimal prediction performance may not be obtained by setting convex loss functions. Simultaneously, it is important to estimate the probability distribution of predictor variables. When the set parametric probability distribution contains more than two parameters, it may be necessary to model multiple parameters to obtain better prediction performance. Therefore, a more generalized regularized tree boosting method is required to make the loss function not limited to the convex function while modelling the tree boosting for multiple parameters, to adapt to the most common parametric probability distributions.
Feature Importance in Gradient Boosting Trees with Cross-Validation Feature Selection
Adler, Afek Ilay, Painsky, Amichai
Gradient Boosting Machines (GBM) are among the go-to algorithms on tabular data, which produce state of the art results in many prediction tasks. Despite its popularity, the GBM framework suffers from a fundamental flaw in its base learners. Specifically, most implementations utilize decision trees that are typically biased towards categorical variables with large cardinalities. The effect of this bias was extensively studied over the years, mostly in terms of predictive performance. In this work, we extend the scope and study the effect of biased base learners on GBM feature importance (FI) measures. We show that although these implementation demonstrate highly competitive predictive performance, they still, surprisingly, suffer from bias in FI. By utilizing cross-validated (CV) unbiased base learners, we fix this flaw at a relatively low computational cost. We demonstrate the suggested framework in a variety of synthetic and real-world setups, showing a significant improvement in all GBM FI measures while maintaining relatively the same level of prediction accuracy.
Secondary control activation analysed and predicted with explainable AI
Kruse, Johannes, Schรคfer, Benjamin, Witthaut, Dirk
The transition to a renewable energy system poses challenges for power grid operation and stability. Secondary control is key in restoring the power system to its reference following a disturbance. Underestimating the necessary control capacity may require emergency measures, such as load shedding. Hence, a solid understanding of the emerging risks and the driving factors of control is needed. In this contribution, we establish an explainable machine learning model for the activation of secondary control power in Germany. Training gradient boosted trees, we obtain an accurate description of control activation. Using SHapely Additive exPlanation (SHAP) values, we investigate the dependency between control activation and external features such as the generation mix, forecasting errors, and electricity market data. Thereby, our analysis reveals drivers that lead to high reserve requirements in the German power system. Our transparent approach, utilizing open data and making machine learning models interpretable, opens new scientific discovery avenues.
Automated Security Assessment for the Internet of Things
Duan, Xuanyu, Ge, Mengmeng, Le, Triet H. M., Ullah, Faheem, Gao, Shang, Lu, Xuequan, Babar, M. Ali
Internet of Things (IoT) based applications face an increasing number of potential security risks, which need to be systematically assessed and addressed. Expert-based manual assessment of IoT security is a predominant approach, which is usually inefficient. To address this problem, we propose an automated security assessment framework for IoT networks. Our framework first leverages machine learning and natural language processing to analyze vulnerability descriptions for predicting vulnerability metrics. The predicted metrics are then input into a two-layered graphical security model, which consists of an attack graph at the upper layer to present the network connectivity and an attack tree for each node in the network at the bottom layer to depict the vulnerability information. This security model automatically assesses the security of the IoT network by capturing potential attack paths. We evaluate the viability of our approach using a proof-of-concept smart building system model which contains a variety of real-world IoT devices and potential vulnerabilities. Our evaluation of the proposed framework demonstrates its effectiveness in terms of automatically predicting the vulnerability metrics of new vulnerabilities with more than 90% accuracy, on average, and identifying the most vulnerable attack paths within an IoT network. The produced assessment results can serve as a guideline for cybersecurity professionals to take further actions and mitigate risks in a timely manner.
Kaggle Competition -- Finding Donors for a Charity with an AUC of 0.94
Comparing Random Forest, Gradient Boosting, and XGBoost to select the best model to predict potential donors for a Charity. This project will employ 3 supervised algorithms, including Random Forest, Gradient Boosting, and XGBoost, to accurately model individuals' income using the 1994 U.S. Census data. I will then choose the best candidate algorithm from preliminary results and further optimize this algorithm to best model the data. My goal with this implementation is to construct a model that accurately predicts whether an individual makes more than 50,000 dollars. This sort of task can arise in a non-profit setting, where organizations survive on donations.
Scalable Feature Selection for (Multitask) Gradient Boosted Trees
Han, Cuize, Rao, Nikhil, Sorokina, Daria, Subbian, Karthik
Gradient Boosted Decision Trees (GBDTs) are widely used for building ranking and relevance models in search and recommendation. Considerations such as latency and interpretability dictate the use of as few features as possible to train these models. Feature selection in GBDT models typically involves heuristically ranking the features by importance and selecting the top few, or by performing a full backward feature elimination routine. On-the-fly feature selection methods proposed previously scale suboptimally with the number of features, which can be daunting in high dimensional settings. We develop a scalable forward feature selection variant for GBDT, via a novel group testing procedure that works well in high dimensions, and enjoys favorable theoretical performance and computational guarantees. We show via extensive experiments on both public and proprietary datasets that the proposed method offers significant speedups in training time, while being as competitive as existing GBDT methods in terms of model performance metrics. We also extend the method to the multitask setting, allowing the practitioner to select common features across tasks, as well as selecting task-specific features.
XGBoost Regression: Explain It To Me Like I'm 10
When I was just starting on my quest to understand Machine Learning algorithms, I would get overwhelmed with all the math-y stuff. I found it difficult to understand the math behind an algorithm without fully grasping the intuition. So I would gravitate towards sources that completely broke down the algorithm into simple steps and made it digestible to someone who never even heard the word Algorithm before. Okay, that is a blatant exaggeration, but you know what I mean. So that's what I'm attempting to do now.
LightAutoML: AutoML Solution for a Large Financial Services Ecosystem
Vakhrushev, Anton, Ryzhkov, Alexander, Savchenko, Maxim, Simakov, Dmitry, Damdinov, Rinchin, Tuzhilin, Alexander
In particular, our ecosystem has the satisfying the set of idiosyncratic requirements that this ecosystem following set of requirements: has for AutoML solutions. Our framework was piloted and deployed in numerous applications and performed at the level of - AutoML system should be able to work with different types the experienced data scientists while building high-quality ML of data collected from hundreds of different information models significantly faster than these data scientists. We also compare systems and often changes more rapidly than these systems the performance of our system with various general-purpose can be fully documented using metadata and painstakingly open source AutoML solutions and show that it performs better for preprocessed by data scientists for the ML tasks using ETL most of the ecosystem and OpenML problems. We also present the tools.