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Title: Obtaining Accurate and Comprehensible Data Mining Models: An Evolutionary Approach
Authors: Johansson, Ulf
Department: University College of Borås. School of Business and Informatics
Issue Date: 2007
Series/Report no.: Linköping studies in science and technology. Dissertations
1086
Publisher: Linköping University, Department of Computer and Information Science
Media type: Text
Publication type: doctoral thesis
Keywords: rule extraction
ensembles
data mining
genetic programming
artificial neural networks
Subject Category: Subject categories::Social Sciences::Computer and Information Science::Computer and Information Science
Subject categories::Social Sciences::Computer and Information Science::Computer and Information Science::Computer Science
Abstract: When performing predictive data mining, the use of ensembles is claimed to virtually guarantee increased accuracy compared to the use of single models. Unfortunately, the problem of how to maximize ensemble accuracy is far from solved. In particular, the relationship between ensemble diversity and accuracy is not completely understood, making it hard to efficiently utilize diversity for ensemble creation. Furthermore, most high-accuracy predictive models are opaque, i.e. it is not possible for a human to follow and understand the logic behind a prediction. For some domains, this is unacceptable, since models need to be comprehensible. To obtain comprehensibility, accuracy is often sacrificed by using simpler but transparent models; a trade-off termed the accuracy vs. comprehensibility trade-off. With this trade-off in mind, several researchers have suggested rule extraction algorithms, where opaque models are transformed into comprehensible models, keeping an acceptable accuracy. In this thesis, two novel algorithms based on Genetic Programming are suggested. The first algorithm (GEMS) is used for ensemble creation, and the second (G-REX) is used for rule extraction from opaque models. The main property of GEMS is the ability to combine smaller ensembles and individual models in an almost arbitrary way. Moreover, GEMS can use base models of any kind and the optimization function is very flexible, easily permitting inclusion of, for instance, diversity measures. In the experimentation, GEMS obtained accuracies higher than both straightforward design choices and published results for Random Forests and AdaBoost. The key quality of G-REX is the inherent ability to explicitly control the accuracy vs. comprehensibility trade-off. Compared to the standard tree inducers C5.0 and CART, and some well-known rule extraction algorithms, rules extracted by G-REX are significantly more accurate and compact. Most importantly, G-REX is thoroughly evaluated and found to meet all relevant evaluation criteria for rule extraction algorithms, thus establishing G-REX as the algorithm to benchmark against.
Description: Avhandling framlagd 2007-06-01 vid Högskolan i Skövde. Opponent: Rögnvaldsson, Thorsteinn, Professor, Sektionen för informationsvetenskap, Data- och Elektroteknik, Högskolan i Halmstad.
URI: http://hdl.handle.net/2320/2136
ISBN: 978-91-85715-34-3
ISSN: 0345-7524
Research information: http://www.hb.se/forskning/forskare.asp?forskareId=ulj
Appears in Collections:Doktorsavhandlingar / Doctoral theses (Informatics)

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