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ITAT 2014. Information Technologies - Applications and Theory. Part II
Kůrková, Věra ; Bajer, Lukáš ; Peška, L. ; Vojtáš, P. ; Holeňa, Martin ; Nehéz, M.
ITAT 2014. Information Technologies - Applications and Theory. Part II. Prague : Institute of Computer Science AS CR, 2014. 145 p. ISBN 978-80-87136-19-5. This volume is the second part of the two-volume proceedings of the 14th conference Information Technologies – Applications and Theory (ITAT 2014), which was held in Jasná, Demänovská Dolina, Slovakia, on September 25–29, 2014. ITAT is a computer science conference with the primary goal of exchanging information on recent research results. Overall, 51 papers were submitted to all conference tracks. This volume presents papers from the workshops and an extended abstract of a poster. Three specialized workshops were held as a part of the conference: Data Mining and Preference Learning on Web, Computational Intelligence and Data Mining, and Algorithmic Aspects of Complex Networks Analysis.
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ITAT 2014. Information Technologies - Applications and Theory. Part I
Kůrková, Věra ; Bajer, Lukáš
ITAT 2014. Information Technologies - Applications and Theory. Part I. Prague : Institute of Computer Science AS CR, 2014. 101 p. ISBN 978-80-87136-18-8. This volume is the first part of the two-volume proceedings of the 14th conference Information Technologies – Applications and Theory (ITAT 2014). The conference was held in Jasná, Demänovská Dolina, Slovakia, on September 25–29, 2014. ITAT is a computer science conference with the primary goal of exchanging information on recent research results between Czech and Slovak scientific communities, and it presents a platform for young researchers and PhD students to start new collaborations. This year, it was held in parallel with two collocated conferences Datakon and Znalosti with which it shared some invited plenary talks and a poster session. Overall, 51 papers were submitted to all conference tracks. This volume presents 16 papers of the main track, which were selected by the program committee based on at least two reviews by the program committee members. Papers from the three workshops and extended abstracts of posters are included in the second volume.
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Meta-Parameters of Kernel Methods and Their Optimization
Vidnerová, Petra ; Neruda, Roman
In this work we deal with the problem of metalearning for kernel based methods. Among the kernel methods we focus on the support vector machine (SVM), that have become a method of choice in a wide range of practical applications, and on the regularization network (RN) with a sound background in approximation theory. We discuss the role of kernel function in learning, and we explain several search methods for kernel function optimization, including grid search, genetic search and simulated annealing. The proposed methodology is demonstrated on experiments using benchmark data sets.
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Online System for Fire Danger Rating in Colorado
Vejmelka, Martin ; Kochanski, A. ; Mandel, J.
A method for the data assimilation of fuel moisture surface observations has been developed for the purpose of incorporation in wildfire forecasting and fire danger rating. In this work, we describe the method itself and also an online computer system that implements the method and combines it with the Real-Time Mesoscale Analysis to track local weather conditions and estimate the fuel moisture content in the state of Colorado. We discuss the construction of the system and future development.
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Case Study in Approaches to the Classification of Audiovisual Recordings of Lectures and Conferences
Pulc, P. ; Holeňa, Martin
Several methods for classification of semistructured documents already exist, thus also classifications for individual modalities of multimedia content. However, every classifier can behave differently on different data modalities and can be differently appropriate for classification of the considered multimedia content as a whole. Because of that, relying on a single classifier or a static weighting of the classification of individual modalities is not adequate. The present paper describes a case study in searching for suitable classification methods, and in investigating appropriate methods for the aggregation of their results to determine a final class of a lecture or conference recording.
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Explaining Anomalies with Sapling Random Forests
Pevný, T. ; Kopp, Martin
The main objective of anomaly detection algorithms is finding samples deviating from the majority. Although a vast number of algorithms designed for this already exist, almost none of them explain, why a particular sample was labelled as an anomaly. To address this issue, we propose an algorithm called Explainer, which returns the explanation of sample’s differentness in disjunctive normal form (DNF), which is easy to understand by humans. Since Explainer treats anomaly detection algorithms as black-boxes, it can be applied in many domains to simplify investigation of anomalies. The core of Explainer is a set of specifically trained trees, which we call sapling random forests. Since their training is fast and memory efficient, the whole algorithm is lightweight and applicable to large databases, datastreams, and real-time problems. The correctness of Explainer is demonstrated on a wide range of synthetic and real world datasets.
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Representations of Boolean Functions by Perceptron Networks
Kůrková, Věra
Limitations of capabilities of shallow perceptron networks are investigated. Lower bounds are derived for growth of numbers of units and sizes of output weights in networks representing Boolean functions of d variables. It is shown that for large d, almost any randomly chosen Boolean function cannot be tractably represented by shallow perceptron networks, i.e., each its representation requires a network with number of units or sizes of output weights depending on d exponentially
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Interpreting and Clustering Outliers with Sapling Random Forests
Kopp, Martin ; Pevný, T. ; Holeňa, Martin
The main objective of outlier detection is finding samples considerably deviating from the majority. Such outliers, often referred to as anomalies, are nowadays more and more important, because they help to uncover interesting events within data. Consequently, a considerable amount of statistical and data mining techniques to identify anomalies was proposed in the last few years, but only a few works at least mentioned why some sample was labelled as an anomaly. Therefore, we propose a method based on specifically trained decision trees, called sapling random forest. Our method is able to interpret the output of arbitrary anomaly detector. The explanation is given as a subset of features, in which the sample is most deviating, or as conjunctions of atomic conditions, which can be viewed as antecedents of logical rules easily understandable by humans. To simplify the investigation of suspicious samples even more, we propose two methods of clustering anomalies into groups. Such clusters can be investigated at once saving time and human efforts. The feasibility of our approach is demonstrated on several synthetic and one real world datasets.
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Robustness of High-Dimensional Data Mining
Kalina, Jan ; Duintjer Tebbens, Jurjen ; Schlenker, Anna
Standard data mining procedures are sensitive to the presence of outlying measurements in the data. This work has the aim to propose robust versions of some existing data mining procedures, i.e. methods resistant to outliers. In the area of classification analysis, we propose a new robust method based on a regularized version of the minimum weighted covariance determinant estimator. The method is suitable for data with the number of variables exceeding the number of observations. The method is based on implicit weights assigned to individual observations. Our approach is a unique attempt to combine regularization and high robustness, allowing to downweight outlying high-dimensional observations. Classification performance of new methods and some ideas concerning classification analysis of high-dimensional data are illustrated on real raw data as well as on data contaminated by severe outliers.
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Important Markov-Chain Properties of (1,lambda)-ES Linear Optimization Models
Chotard, A. ; Holeňa, Martin
Several recent publications investigated Markov-chain modelling of linear optimization by a (1,lambda)-ES, considering both unconstrained and linearly constrained optimization, and both constant and varying step size. All of them assume normality of the involved random steps. This is a very strong and specific assumption. The objective of our contribution is to show that in the constant step size case, valuable properties of the Markov chain can be obtained even for steps with substantially more general distributions. Several results that have been previously proved using the normality assumption are proved here in a more general way without that assumption. Finally, the decomposition of a multidimensional distribution into its marginals and the copula combining them is applied to the new distributional assumptions, particular attention being paid to distributions with Archimedean copulas.
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