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A zone diagram is a certain geometric object which a variation on the notion of Voronoi diagram. It was introduced by Tetsuo Asano, Jiri Matousek, and Takeshi Tokuyama in 2007.〔 Formally, it is a fixed point of a certain function. Its existence or uniqueness are not clear in advance and have been established only in specific cases. Its computation is not obvious too. ==A particular but informative case== Consider a group of different pointuu in the Euclidean plane. Each point is called a site. When we speak about the Voronoi diagram induced by these sites, we associate to the site the set of all points in the plane whose distance to the given site is not greater to their distance to any other site . The collection of these regions is the Voronoi diagram associated with these sites, and it induces a decomposition of the plane into regions: the Voronoi regions (Voronoi cells). In a zone diagram the region associated with the site is defined a little bit differently: instead of associating it the set of all points whose distance to is not greater than their distance to the other sites, we associate to the set of all points in the plane whose distance to is not greater than their distance to any other region. Formally, :. Here denotes the euclidean distance between the points and and is the distance between the point and the set . In addition, since we consider the plane. The tuple is the zone diagram associated with the sites. The problem with this definition is that it seems circular: in order to know we should know for each index but each such is defined in terms of . On a second thought, we see that actually the tuple is a solution of the following system of equations: : Rigorously, a zone diagram is any solution of this system, if such a solution exists. This definition can be extended without essentially any change to higher dimensions, to sites which are not necessarily points, to infinitely many sites, etc. 抄文引用元・出典: フリー百科事典『 ウィキペディア(Wikipedia)』 ■ウィキペディアで「Zone diagram」の詳細全文を読む スポンサード リンク
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