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LikelihoodBased Robust Classification with Bayesian Networks
"... Abstract. Bayesian networks are commonly used for classification: a structural learning algorithm determines the network graph, while standard approaches estimate the model parameters from data. Yet, with few data the corresponding assessments can be unreliable. To gain robustness in this phase, we ..."
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Abstract. Bayesian networks are commonly used for classification: a structural learning algorithm determines the network graph, while standard approaches estimate the model parameters from data. Yet, with few data the corresponding assessments can be unreliable. To gain robustness in this phase, we consider a likelihoodbased learning approach, which takes all the model quantifications whose likelihood exceeds a given threshold. A new classification algorithm based on this approach is presented. Notably, this is a credal classifier, i.e., more than a single class can be returned in output. This is the case when the Bayesian networks consistent with the threshold constraint assign different class labels to a test instance. This is the first classifier of this kind for general topologies. Experiments show how this approach provide the desired robustness.
LikelihoodBased Robust Classification with Bayesian Networks
, 2012
"... Bayesian networks are commonly used for classification: a structural learning algorithm determines the network graph, while standard approaches estimate the model parameters from data. Yet, with few data the corresponding assessments can be unreliable. To gain robustness in this phase, we consider a ..."
Abstract
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Bayesian networks are commonly used for classification: a structural learning algorithm determines the network graph, while standard approaches estimate the model parameters from data. Yet, with few data the corresponding assessments can be unreliable. To gain robustness in this phase, we consider a likelihoodbased learning approach, which takes all the model quantifications whose likelihood exceeds a given threshold. A new classification algorithm based on this approach is presented. Notably, this is a credal classifier, i.e., more than a single class can be returned in output. This is the case when the Bayesian networks consistent with the threshold constraint assign different class labels to a test instance. This is the first classifier of this kind for general topologies. Experiments show how this approach provide the desired robustness. 1
Compressionbased AODE Classifiers
"... Abstract. We propose the COMPAODE classifier, which adopts the compressionbased approach [1] to average the posterior probabilities computed by different nonnaive classifiers (SPODEs). COMPAODE improves classification performance over the wellknown AODE [10] model. COMPAODE assumes a uniform pr ..."
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Abstract. We propose the COMPAODE classifier, which adopts the compressionbased approach [1] to average the posterior probabilities computed by different nonnaive classifiers (SPODEs). COMPAODE improves classification performance over the wellknown AODE [10] model. COMPAODE assumes a uniform prior over the SPODEs; we then develop the credal classifier COMPAODE*, substituting the uniform prior by a set of priors. COMPAODE * returns more classes when the classification is priordependent, namely if the most probable class varies with the prior adopted over the SPODEs. COMPAODE * achieves higher classification utility than both COMPAODE and AODE. 1
Credal Ensembles of Classifiers
"... It is studied how to aggregate the probabilistic predictions generated by different SPODE (SuperParentOneDependence Estimators) classifiers. It is shown that aggregating such predictions via compressionbased weights achieves a slight but consistent improvement of performance over previously exis ..."
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It is studied how to aggregate the probabilistic predictions generated by different SPODE (SuperParentOneDependence Estimators) classifiers. It is shown that aggregating such predictions via compressionbased weights achieves a slight but consistent improvement of performance over previously existing aggregation methods, including Bayesian Model Averaging and simple average (the approach adopted by the AODE algorithm). Then, attention is given to the problem of choosing the prior probability distribution over the models; this is an important issue in any Bayesian ensemble of models. To robustly deal with the choice of the prior, the single prior over the models is substituted by a set of priors over the models (credal set), thus obtaining a credal ensemble of Bayesian classifiers. The credal ensemble recognizes the priordependent instances, namely the instances whose most probable class varies when different prior over the models are considered. When faced with priordependent instances, the credal ensemble remains reliable by returning a set of classes rather than a single class. Two credal ensembles of SPODEs are developed; the first generalizes the Bayesian Model Averaging and the second the compressionbased aggregation. Extensive experiments show that the novel ensembles compare favorably to traditional methods for aggregating SPODEs and also to previous credal classifiers.
LikelihoodBased Robust Classification with Bayesian Networks
, 2012
"... Bayesian networks are commonly used for classification: a structural learning algorithm determines the network graph, while standard approaches estimate the model parameters from data. Yet, with few data the corresponding assessments can be unreliable. To gain robustness in this phase, we consider a ..."
Abstract
 Add to MetaCart
Bayesian networks are commonly used for classification: a structural learning algorithm determines the network graph, while standard approaches estimate the model parameters from data. Yet, with few data the corresponding assessments can be unreliable. To gain robustness in this phase, we consider a likelihoodbased learning approach, which takes all the model quantifications whose likelihood exceeds a given threshold. A new classification algorithm based on this approach is presented. Notably, this is a credal classifier, i.e., more than a single class can be returned in output. This is the case when the Bayesian networks consistent with the threshold constraint assign different class labels to a test instance. This is the first classifier of this kind for general topologies. Experiments show how this approach provide the desired robustness. 1