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This thesis presents the development of a novel fuzzy regression tree algorithm known as Elgasir, which is based on the CHAID regression tree algorithm and Takagi-Sugeno fuzzy inference. The Elgasir Algorithm is applied to crisp regression trees to produce fuzzy regression trees in order to soften sharp decision boundaries inherited in crisp trees. Elgasir generates a fuzzy rule base by applying fuzzy techniques to crisp regression trees using Trapezoidal membership functions. Then Takagi-Sugeno fuzzy inference is used to aggregate the final output from the fuzzy implications. A novel optimization method based on the Artificial Immune Network model (opt-aiNet) is also proposed to optimize the fuzzification of fuzzy regression trees generated by the Elgasir Algorithm. Finally, the Elgasir Algorithm is developed further by proposing a new approach to creating fuzzy regression tree forests based upon the induction of multiple fuzzy regression decision trees from one training sample, where each tree will represent a different view of the data domain. A significant number of experiments were carried out for each of the proposed approaches, using five real-world regression problems from the VCI repository and KEEL repository. The empirical results have shown the effectiveness of using the proposed methods by increasing the prediction accuracy and robustness of fuzzy regression trees.

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Στην παρούσα διπλωματική εργασία παρουσιάζονται τα ιατρικά συστήματα λήψης απόφασης (MDSS) και αρχιτεκτονικές ανάπτυξή τους. Πραγματεύεται τις έννοιες του ευφυούς ελέγχου και της ασάφειας για να καταλήξει στον όρο Ασαφή Γνωστικά Δίκτυα(FCΜ). Αφού περιγράφεται αναλυτικά η ανάπτυξή, ο καθορισμός των παραμέτρων και οι μεθοδολογίες εκμάθησης ενός Ασαφούς Γνωστικού Δικτύου, καταλήγει τελικά στην εφαρμογή τους στον χώρο της ιατρικής. Τέλος, ακολουθεί το μοντέλο ενός Ασαφούς Ελεγκτή για ιατρικές εφαρμογές και η ανάπτυξη ενός MDSS για την εύρεση Κάκωσης Γόνατος με αρχιτεκτονικές Ανταγωνιστικού Ασαφούς Γνωστικού Δικτύου (CFCΜ). / The thesis represents the medical decision support systems (MDSS) and their architecture. Starting with the concepts of intelligent control and Fuzzy Cognitive Maps (FCM), it describes in detail the development, the setting parameters, and the learning methods of FCMs, with the purpose of their application into the field of medicine. Finally, it illustrates the model of a Fuzzy Controller for medical applications and the development of an MDSS for finding knee injury with the architecture of Competitive FCMs (CFCM).