title: Midpoints for fuzzy sets and their application in medicine.
abstract: Using Kosko's hypercube, we identify a fuzzy set with a point in a unit hypercube. A non-fuzzy or crisp subset of a set is a vertex of the hypercube. We introduce some new ideas: the definition of the fuzzy segment joining two given fuzzy subsets of a set, the set of midpoints between those two fuzzy subsets, and the set of equidistant points from given points. We present some basic properties and relations between these concepts and provide a complete description of fuzzy segments and midpoints. In the majority of cases, there is no unique midpoint; one has an infinite set of possibilities to choose from. This situation is totally different from classical Euclidean geometry where, for two given points, there is a unique midpoint. We use the obtained results to study two sets of medical data and present two applications in medicine: the fuzzy degree of two concurrent food and drug addictions, and a fuzzy representation of concomitant causal mechanisms of stroke.
authors.affiliation: Departamento de Análisis Matemático, Facultad de Matemáticas, Universidad de Santiago de Compostela, 15782 Santiago de Compostela, Spain. amnieto@usc.es
authors.forename: Juan J
authors.initials: JJ
authors.lastname: Nieto
authors.forename: Angela
authors.initials: A
authors.lastname: Torres
mesh_terms: D000293:Adolescent; D000428:Alcohol Drinking / Q000453:epidemiology; D002648:Child; D003430:Cross-Sectional Studies; D003658:Decision Making, Computer-Assisted; D020000:Decision Support Systems, Clinical; D017143:Fuzzy Logic; D006801:Humans; D008432:Mathematical Computing; D012907:Smoking / Q000453:epidemiology; D020521:Stroke / Q000453:epidemiology; D019966:Substance-Related Disorders / Q000175:diagnosis