Sánchez Carpena, Gracia

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Sánchez Carpena, Gracia

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Sánchez Carpena, Gracia

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Universidad de Murcia. Departamento de Ingeniería de la Informacióny las Comunicaciones

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Open Access
Towards semi-automatic human performance evaluation: The case study of a contact center
(IOS Press, 2018-06-27) Brunello, Andrea; Jiménez Barrionuevo, Fernando; Marzano, Enrico; Palma Méndez, José Tomás; Sánchez Carpena, Gracia; Sciavicco, Guido; Ingeniería de la Información y las Comunicaciones; Department of Mathematics, Physics, and Computer Science, University of Udine, Udine, Italy; R&D Department, Gap Srlu, Trieste, Italy; Department of Mathematics and Computer Science, University of Ferrara, Ferrara, Italy
Evaluating in a correct, fair, systematic and reliable way the quality of the work is a central problem in modern business. Both from the psychological and the social point of view, this problem is very far away from being solved, let alone from being managed by a (semi-) automatic decision support system. In this paper we consider the case study of evaluating the operators’ work quality in a medium-sized contact center, and, in particular, the problem of selecting the correct variables to be used in such an evaluation. Starting from a data set representative of the company’s range and size of activities, that allowed no usable predictive model for evaluating the skills of the agents, we were able to devise a reproducible methodology, along with an a posteriori optimization process, to select the essential variables that should be used to objectively evaluate the quality of the agents’ work. These results may be used in a support system helping the supervisors in evaluating the agents’ performances. Moreover, we believe that our methodology may be extrapolated and reused in other comparable contexts characterized by the measurability of the human operators’ performance.
Open Access
Multi-objective evolutionary algorithms for fuzzy classification in survival prediction
(2014) Jiménez Barrionuevo, Fernando; Sánchez Carpena, Gracia; Juárez Herrero, José Manuel; Ingeniería de la Información y las Comunicaciones
bjective This paper presents a novel rule-based fuzzy classification methodology for survival/mortality prediction in severe burnt patients. Due to the ethical aspects involved in this medical scenario, physicians tend not to accept a computer-based evaluation unless they understand why and how such a recommendation is given. Therefore, any fuzzy classifier model must be both accurate and interpretable. Methods and materials The proposed methodology is a three-step process: (1) multi-objective constrained optimization of a patient's data set, using Pareto-based elitist multi-objective evolutionary algorithms to maximize accuracy and minimize the complexity (number of rules) of classifiers, subject to interpretability constraints; this step produces a set of alternative (Pareto) classifiers; (2) linguistic labeling, which assigns a linguistic label to each fuzzy set of the classifiers; this step is essential to the interpretability of the classifiers; (3) decision making, whereby a classifier is chosen, if it is satisfactory, according to the preferences of the decision maker. If no classifier is satisfactory for the decision maker, the process starts again in step (1) with a different input parameter set. Results The performance of three multi-objective evolutionary algorithms, niched pre-selection multi-objective algorithm, elitist Pareto-based multi-objective evolutionary algorithm for diversity reinforcement (ENORA) and the non-dominated sorting genetic algorithm (NSGA-II), was tested using a patient's data set from an intensive care burn unit and a standard machine learning data set from an standard machine learning repository. The results are compared using the hypervolume multi-objective metric. Besides, the results have been compared with other non-evolutionary techniques and validated with a multi-objective cross-validation technique. Our proposal improves the classification rate obtained by other non-evolutionary techniques (decision trees, artificial neural networks, Naive Bayes, and case-based reasoning) obtaining with ENORA a classification rate of 0.9298, specificity of 0.9385, and sensitivity of 0.9364, with 14.2 interpretable fuzzy rules on average. Conclusions Our proposal improves the accuracy and interpretability of the classifiers, compared with other non-evolutionary techniques. We also conclude that ENORA outperforms niched pre-selection and NSGA-II algorithms. Moreover, given that our multi-objective evolutionary methodology is non-combinational based on real parameter optimization, the time cost is significantly reduced compared with other evolutionary approaches existing in literature based on combinational optimization.
Open Access
Multi-objective evolutionary simultaneous feature selection and outlier detection for regression
(Institute of Electrical and Electronics Engineers, 2021-09-27) Jiménez Barrionuevo, Fernando; Lucena Sánchez, Estrella; Sánchez Carpena, Gracia; Sciavicco, Guido; Ingeniería de la Información y las Comunicaciones; Facultades de la UMU::Facultad de Informática
When investigating the causes of contamination in specific contexts, such as in underground water wells, multivariate regression is commonly used to establish possible links between the chemical-physical values of the samples and the levels of contaminant. Two issues often arise from such a statistical analysis: selecting the best predicting variables and detecting the instances that can be suspected to be outliers. In this paper, we propose a comprehensive, integrated, and general optimization model that solves these two problems simultaneously in such a way that outliers can be detected in reference to the specific variables that are selected for the regression, and we implement such an optimization model with a well-known evolutionary algorithm. We test our proposal on data extracted from a project whose aim is to establish the causes of the contamination of underwater water wells in a very specific area of northeastern Italy. The results show that our variable selection and outlier detection algorithm allows the synthesis of very reliable, interpretable, and clean regression models.
Open Access
Sensitivity-constrained evolutionary feature selection for imbalanced medical classification: a case study on rotator cull tear surgery prediction
(MDPI, 2025-12-08) Belmonte, José María; Jiménez Barrionuevo, Fernando; Sánchez Carpena, Gracia; Gabardo, Santiago; Martínez Catalán, Natalia; Calvo, Emilio; Bernabé García, Gregorio; García Carrasco, José Manuel; Ingeniería de la Información y las Comunicaciones; Facultades de la UMU::Facultad de Informática
While most patients with degenerative rotator cuff tears respond to conservative treatment, a minority progress to surgery. To anticipate these cases under class imbalance, we propose a sensitivity-constrained evolutionary feature selection framework prioritizing surgical-class recall, benchmarked against traditional methods. Two variants are proposed: (i) a single-objective search maximizing balanced accuracy and (ii) a multi-objective search also minimizing the number of selected features. Both enforce a minimum-sensitivity constraint on the minority class to limit false negatives. The dataset includes 347 patients (66 surgical, 19%) described by 28 clinical, imaging, symptom, and functional variables. We compare against 62 widely adopted pipelines, including oversampling, undersampling, hybrid resampling, cost-sensitive classifiers, and imbalance-aware ensembles. The main metric is balanced accuracy, with surgical-class F1-score as secondary. PairwiseWilcoxon tests with a win–loss ranking assessed statistical significance. Evolutionary models rank among the top; the multi-objective variant with a Balanced Bagging Classifier performs best, achieving a mean balanced accuracy of 0.741. Selected subsets recurrently include age, tear location/severity, comorbidities, and pain/functional scores, matching clinical expectations. The constraint preserved minority-class recall without discarding or synthesizing data. Sensitivity-constrained evolutionary feature selection thus offers a data-preserving, interpretable solution for pre-surgical decision support, improving balanced performance and supporting safer triage decisions.
Open Access
Multi-objective evolutionary feature selection for ensemble learning with random forests in time series forecasting
(Elsevier, 2025-11-10) Espinosa, Raquel; Sánchez Carpena, Gracia; Palma Méndez, José Tomás; Jiménez Barrionuevo, Fernando; Ingeniería de la Información y las Comunicaciones; Facultades de la UMU::Facultad de Informática
Time series forecasting is fundamental in numerous domains, including finance, healthcare, energy, and environmental monitoring. However, the high dimensionality of feature spaces can lead to overfitting and reduced interpretability, making feature selection a crucial preprocessing step. This paper proposes a multiobjective evolutionary algorithm for feature selection in time series forecasting, designed to enhance predictive accuracy while improving generalization. The method partitions the dataset, associating each partition with an objective function in the optimization process. By independently selecting relevant feature subsets, it generates a Pareto front of Random Forest models, each trained on a distinct subset of features. These models are then aggregated into a stacking-based ensemble framework, effectively balancing feature relevance and diversity. Additionally, we introduce a feature importance measure based on selection frequency in the non-dominated solutions of the optimization process. To validate our approach, we conduct experiments on real-world forecasting tasks, including air quality prediction in southeastern Spain and Italy and oil temperature forecasting in industrial applications. We also evaluate performance on synthetic datasets of increasing complexity, systematically varying instances, features, seasonality, noise, and trends. The proposed method is compared against conventional Random Forest, a wrapper-based feature selection method with a multiobjective evolutionary search strategy, and several state-of-the-art embedded feature selection techniques for time series forecasting. The results demonstrate that our approach significantly improves forecasting accuracy while mitigating overfitting. By integrating multi-objetive evolutionary optimization, random forest, ensemble learning, and a novel feature importance measure, our method offers a robust, interpretable, and effective feature selection for time series forecasting applications.
Open Access
Multiobjective evolutionary feature selection for fuzzy classification
(Institute of Electrical and Electronics Engineers, 2019-05) Jiménez Barrionuevo, Fernando; Martínez, Carlos; Marzano, Enrico; Palma Méndez, José Tomás; Sánchez Carpena, Gracia; Sciavicco, Guido; Ingeniería de la Información y las Comunicaciones
The interpretability of classification systems refers to the ability of these to express their behavior in a way that is easily understandable by a user. Interpretable classification models allow for external validation by an expert and, in certain disciplines, such as medicine or business, providing information about decision making is essential for ethical and human reasons. Fuzzy rule based classification systems are consolidated powerful classification tools based on fuzzy logic and designed to produce interpretable models; however, in presence of a large number of attributes, even rule-based models tend to be too complex to be easily interpreted. In this paper, we propose a novel multivariate feature selection method in which both search strategy and classifier are based on multiobjective evolutionary computation. We designed a set of experiments to establish an acceptable setting with respect to the number of evaluations required by the search strategy and by the classifier. We tested our strategy on a real-life dataset and compared the results against a wide range of feature selection methods that includes filter, wrapper, multivariate, and univariate methods, with deterministic and probabilistic search strategies, and with evaluators of diverse nature. Finally, the fuzzy rule based classification model obtained with the proposed method has been evaluated with standard performance metrics and compared with other well-known fuzzy rule based classifiers. We have used two real-life datasets extracted from a contact center; in one case, with the proposed method, we obtained an accuracy of 0.7857 with eight rules, while the best fuzzy classifier compared obtained 0.7679 with eight rules, and in the second case, we obtained an accuracy of 0.7403 with five rules, while the best fuzzy classifier compared obtained 0.6364 with four rules.