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...erformance using receiver operating characteristic (ROC) curves. We then illustrate their use on real-life medical diagnostic tasks. 1 Introduction. Since their introduction by Vapnik and coworkers [ =-=Vapnik, 1995-=-; Cortes and Vapnik, 1995 ] , Support Vector Machines (SVMs) have been successfully applied to a number of real world problems such as handwritten character and digit recognition [ Scholkopf, 1997; C...

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...Vapnik, 1995 ] , Support Vector Machines (SVMs) have been successfully applied to a number of real world problems such as handwritten character and digit recognition [ Scholkopf, 1997; Cortes, 1995; =-=LeCun et al., 1995-=-; Vapnik, 1995 ] , face detection [ Osuna et al., 1997 ] and speaker identication [ Schmidt, 1996 ] . They exhibit a remarkable resistance to overtting, a feature explained by the fact that they dir...

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...C P k i + hw;wi subject to y i (hw;x i i+ b) 1 i , with i 0 (3) with k = 1 and k = 2. A theoretical analysis of both algorithms has recently been provided by Shawe-Taylor and Cristianini [ =-=Shawe-Taylor and Cristianini, 1999-=- ] , based on the concept of \margin distributions". For many decision support systems it is important to distinguish the two types of errors that can arise: a false alarm is usually not as expensive ...

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...d problems such as handwritten character and digit recognition [ Scholkopf, 1997; Cortes, 1995; LeCun et al., 1995; Vapnik, 1995 ] , face detection [ Osuna et al., 1997 ] and speaker identication [ =-=Schmidt, 1996-=- ] . They exhibit a remarkable resistance to overtting, a feature explained by the fact that they directly implement the principle of Structural Risk Minimization [ Vapnik, 1995 ] . For noise-free cl...

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...of correctly classied individuals without the disease. ROC analysis is a classical method in Signal Detection Theory [ Swets and Pickett, 1982 ] , and is used also in statistics, medical diagnosis [ =-=Centor, 1991-=- ] and more recently in Machine Learning as an alternative method for comparing learning systems [ Provost et al., 1998 ] . ROC space denotes a coordinate system used for visualizing the performance o...

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... related technique to the one proposed in this paper. Studying the case of very imbalanced datasets (where points of one class are much more numerous than points of the other class), the authors of [ =-=Karakoulas and Shawe-Taylor, 1999-=- ] proposed an algorithm where the labels are changed in such a way as to obtain a larger margin on the side of the smaller class. 2.1. We can readily generalise the soft margin approach (3): w x i ...

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...5; Cortes and Vapnik, 1995 ] , Support Vector Machines (SVMs) have been successfully applied to a number of real world problems such as handwritten character and digit recognition [ Scholkopf, 1997; =-=Cortes, 1995-=-; LeCun et al., 1995; Vapnik, 1995 ] , face detection [ Osuna et al., 1997 ] and speaker identication [ Schmidt, 1996 ] . They exhibit a remarkable resistance to overtting, a feature explained by th...

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...Theory [ Swets and Pickett, 1982 ] , and is used also in statistics, medical diagnosis [ Centor, 1991 ] and more recently in Machine Learning as an alternative method for comparing learning systems [ =-=Provost et al., 1998-=- ] . ROC space denotes a coordinate system used for visualizing the performance of a classier, where the true positive rate is plotted on the y-axis, and the false positive rate on the x-axis. In thi...

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... part of the latter curve could be plotted though this feature would depend on the training algorithm used [ Friess et al., 1998 ] . 4. TB dataset. This dataset derives from one of our own projects [ =-=Veropoulos et al., 1998-=-; 1999 ] . The task involves classication of image objects (TB bacilli or non-bacilli) on images captured using a microscope. It is intended as part of a system being developed for semi-automated dia...