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Alexander Statnikov

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5 papers

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JMLR Journal 2015 Journal Article

Ultra-Scalable and Efficient Methods for Hybrid Observational and Experimental Local Causal Pathway Discovery

Alexander Statnikov
Sisi Ma
Mikael Henaff
Nikita Lytkin
Efstratios Efstathiadis
Eric R. Peskin
Constantin F. Aliferis

Discovery of causal relations from data is a fundamental objective of several scientific disciplines. Most causal discovery algorithms that use observational data can infer causality only up to a statistical equivalency class, thus leaving many causal relations undetermined. In general, complete identification of causal relations requires experimentation to augment discoveries from observational data. This has led to the recent development of several methods for active learning of causal networks that utilize both observational and experimental data in order to discover causal networks. In this work, we focus on the problem of discovering local causal pathways that contain only direct causes and direct effects of the target variable of interest and propose new discovery methods that aim to minimize the number of required experiments, relax common sufficient discovery assumptions in order to increase discovery accuracy, and scale to high-dimensional data with thousands of variables. We conduct a comprehensive evaluation of new and existing methods with data of dimensionality up to 1,000,000 variables. We use both artificially simulated networks and in-silico gene transcriptional networks that model the characteristics of real gene expression data. [abs] [ pdf ][ bib ] &copy JMLR 2015. ( edit, beta )

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JMLR Journal 2013 Journal Article

Algorithms for Discovery of Multiple Markov Boundaries

Alexander Statnikov
Nikita I. Lytkin
Jan Lemeire
Constantin F. Aliferis

Algorithms for Markov boundary discovery from data constitute an important recent development in machine learning, primarily because they offer a principled solution to the variable/feature selection problem and give insight on local causal structure. Over the last decade many sound algorithms have been proposed to identify a single Markov boundary of the response variable. Even though faithful distributions and, more broadly, distributions that satisfy the intersection property always have a single Markov boundary, other distributions/data sets may have multiple Markov boundaries of the response variable. The latter distributions/data sets are common in practical data-analytic applications, and there are several reasons why it is important to induce multiple Markov boundaries from such data. However, there are currently no sound and efficient algorithms that can accomplish this task. This paper describes a family of algorithms TIE* that can discover all Markov boundaries in a distribution. The broad applicability as well as efficiency of the new algorithmic family is demonstrated in an extensive benchmarking study that involved comparison with 26 state-of-the-art algorithms/variants in 15 data sets from a diversity of application domains. [abs] [ pdf ][ bib ] &copy JMLR 2013. ( edit, beta )

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JMLR Journal 2010 Journal Article

Local Causal and Markov Blanket Induction for Causal Discovery and Feature Selection for Classification Part I: Algorithms and Empirical Evaluation

Constantin F. Aliferis
Alexander Statnikov
Ioannis Tsamardinos
Subramani Mani
Xenofon D. Koutsoukos

We present an algorithmic framework for learning local causal structure around target variables of interest in the form of direct causes/effects and Markov blankets applicable to very large data sets with relatively small samples. The selected feature sets can be used for causal discovery and classification. The framework ( Generalized Local Learning, or GLL) can be instantiated in numerous ways, giving rise to both existing state-of-the-art as well as novel algorithms. The resulting algorithms are sound under well-defined sufficient conditions. In a first set of experiments we evaluate several algorithms derived from this framework in terms of predictivity and feature set parsimony and compare to other local causal discovery methods and to state-of-the-art non-causal feature selection methods using real data. A second set of experimental evaluations compares the algorithms in terms of ability to induce local causal neighborhoods using simulated and resimulated data and examines the relation of predictivity with causal induction performance. Our experiments demonstrate, consistently with causal feature selection theory, that local causal feature selection methods (under broad assumptions encompassing appropriate family of distributions, types of classifiers, and loss functions) exhibit strong feature set parsimony, high predictivity and local causal interpretability. Although non-causal feature selection methods are often used in practice to shed light on causal relationships, we find that they cannot be interpreted causally even when they achieve excellent predictivity. Therefore we conclude that only local causal techniques should be used when insight into causal structure is sought. In a companion paper we examine in depth the behavior of GLL algorithms, provide extensions, and show how local techniques can be used for scalable and accurate global causal graph learning. [abs] [ pdf ][ bib ] &copy JMLR 2010. ( edit, beta )

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JMLR Journal 2010 Journal Article

Local Causal and Markov Blanket Induction for Causal Discovery and Feature Selection for Classification Part II: Analysis and Extensions

Constantin F. Aliferis
Alexander Statnikov
Ioannis Tsamardinos
Subramani Mani
Xenofon D. Koutsoukos

In part I of this work we introduced and evaluated the Generalized Local Learning (GLL) framework for producing local causal and Markov blanket induction algorithms. In the present second part we analyze the behavior of GLL algorithms and provide extensions to the core methods. Specifically, we investigate the empirical convergence of GLL to the true local neighborhood as a function of sample size. Moreover, we study how predictivity improves with increasing sample size. Then we investigate how sensitive are the algorithms to multiple statistical testing, especially in the presence of many irrelevant features. Next we discuss the role of the algorithm parameters and also show that Markov blanket and causal graph concepts can be used to understand deviations from optimality of state-of-the-art non-causal algorithms. The present paper also introduces the following extensions to the core GLL framework: parallel and distributed versions of GLL algorithms, versions with false discovery rate control, strategies for constructing novel heuristics for specific domains, and divide-and-conquer local-to-global learning (LGL) strategies. We test the generality of the LGL approach by deriving a novel LGL-based algorithm that compares favorably to the state-of-the-art global learning algorithms. In addition, we investigate the use of non-causal feature selection methods to facilitate global learning. Open problems and future research paths related to local and local-to-global causal learning are discussed. [abs] [ pdf ][ bib ] &copy JMLR 2010. ( edit, beta )

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AAAI Conference 2005 System Paper

Using the GEMS System for Cancer Diagnosis and Biomarker Discovery from Microarray Gene Expression Data

Alexander Statnikov

We will demonstrate the GEMS system for automated development and evaluation of high-quality cancer diagnostic models and biomarker discovery from microarray gene expression data. The development of GEMS was informed by the results of an extensive algorithmic evaluation using 11 microarray datasets. The system was further evaluated in two cross-dataset applications and using 5 microarray datasets. The performance of models produced by GEMS is comparable or better than the results obtained by human analysts, and these models generalize well to independent samples in cross-dataset applications. The system is freely available for download from http: //www. gems-system. org for noncommercial use.

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