122,572 research outputs found
Improving Stability in Decision Tree Models
Owing to their inherently interpretable structure, decision trees are
commonly used in applications where interpretability is essential. Recent work
has focused on improving various aspects of decision trees, including their
predictive power and robustness; however, their instability, albeit
well-documented, has been addressed to a lesser extent. In this paper, we take
a step towards the stabilization of decision tree models through the lens of
real-world health care applications due to the relevance of stability and
interpretability in this space. We introduce a new distance metric for decision
trees and use it to determine a tree's level of stability. We propose a novel
methodology to train stable decision trees and investigate the existence of
trade-offs that are inherent to decision tree models - including between
stability, predictive power, and interpretability. We demonstrate the value of
the proposed methodology through an extensive quantitative and qualitative
analysis of six case studies from real-world health care applications, and we
show that, on average, with a small 4.6% decrease in predictive power, we gain
a significant 38% improvement in the model's stability
On The Stability of Interpretable Models
Interpretable classification models are built with the purpose of providing a
comprehensible description of the decision logic to an external oversight
agent. When considered in isolation, a decision tree, a set of classification
rules, or a linear model, are widely recognized as human-interpretable.
However, such models are generated as part of a larger analytical process. Bias
in data collection and preparation, or in model's construction may severely
affect the accountability of the design process. We conduct an experimental
study of the stability of interpretable models with respect to feature
selection, instance selection, and model selection. Our conclusions should
raise awareness and attention of the scientific community on the need of a
stability impact assessment of interpretable models
Technical note: Bias and the quantification of stability
Research on bias in machine learning algorithms has generally been concerned with the
impact of bias on predictive accuracy. We believe that there are other factors that should
also play a role in the evaluation of bias. One such factor is the stability of the algorithm;
in other words, the repeatability of the results. If we obtain two sets of data from the same
phenomenon, with the same underlying probability distribution, then we would like our
learning algorithm to induce approximately the same concepts from both sets of data. This
paper introduces a method for quantifying stability, based on a measure of the agreement
between concepts. We also discuss the relationships among stability, predictive accuracy,
and bias
Classification hardness for supervised learners on 20 years of intrusion detection data
This article consolidates analysis of established (NSL-KDD) and new intrusion detection datasets (ISCXIDS2012, CICIDS2017, CICIDS2018) through the use of supervised machine learning (ML) algorithms. The uniformity in analysis procedure opens up the option to compare the obtained results. It also provides a stronger foundation for the conclusions about the efficacy of supervised learners on the main classification task in network security. This research is motivated in part to address the lack of adoption of these modern datasets. Starting with a broad scope that includes classification by algorithms from different families on both established and new datasets has been done to expand the existing foundation and reveal the most opportune avenues for further inquiry. After obtaining baseline results, the classification task was increased in difficulty, by reducing the available data to learn from, both horizontally and vertically. The data reduction has been included as a stress-test to verify if the very high baseline results hold up under increasingly harsh constraints. Ultimately, this work contains the most comprehensive set of results on the topic of intrusion detection through supervised machine learning. Researchers working on algorithmic improvements can compare their results to this collection, knowing that all results reported here were gathered through a uniform framework. This work's main contributions are the outstanding classification results on the current state of the art datasets for intrusion detection and the conclusion that these methods show remarkable resilience in classification performance even when aggressively reducing the amount of data to learn from
Verifiable Reinforcement Learning via Policy Extraction
While deep reinforcement learning has successfully solved many challenging
control tasks, its real-world applicability has been limited by the inability
to ensure the safety of learned policies. We propose an approach to verifiable
reinforcement learning by training decision tree policies, which can represent
complex policies (since they are nonparametric), yet can be efficiently
verified using existing techniques (since they are highly structured). The
challenge is that decision tree policies are difficult to train. We propose
VIPER, an algorithm that combines ideas from model compression and imitation
learning to learn decision tree policies guided by a DNN policy (called the
oracle) and its Q-function, and show that it substantially outperforms two
baselines. We use VIPER to (i) learn a provably robust decision tree policy for
a variant of Atari Pong with a symbolic state space, (ii) learn a decision tree
policy for a toy game based on Pong that provably never loses, and (iii) learn
a provably stable decision tree policy for cart-pole. In each case, the
decision tree policy achieves performance equal to that of the original DNN
policy
Stochastic Coalitional Better-response Dynamics and Strong Nash Equilibrium
We consider coalition formation among players in an n-player finite strategic
game over infinite horizon. At each time a randomly formed coalition makes a
joint deviation from a current action profile such that at new action profile
all players from the coalition are strictly benefited. Such deviations define a
coalitional better-response (CBR) dynamics that is in general stochastic. The
CBR dynamics either converges to a strong Nash equilibrium or stucks in a
closed cycle. We also assume that at each time a selected coalition makes
mistake in deviation with small probability that add mutations (perturbations)
into CBR dynamics. We prove that all strong Nash equilibria and closed cycles
are stochastically stable, i.e., they are selected by perturbed CBR dynamics as
mutations vanish. Similar statement holds for strict strong Nash equilibrium.
We apply CBR dynamics to the network formation games and we prove that all
strongly stable networks and closed cycles are stochastically stable
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