The dystonias are movement disorders in which sustained muscle contractions cause twisting and repetitive movements or abnormal postures. The movements, which are involuntary and sometimes painful, may affect a single muscle; a group of muscles such as those in the arms, legs, or neck; or the entire body.
Definition of Data Clustering. Data Clustering is the classification of a data set into a group of numbers, where members of each group surround a particular number.efinition of Data Clustering. Data Clustering is the classification of a data set into a group of numbers, where members of each group surround a particular number.
Cluster algebras are a class of commutative rings introduced by Fomin and Zelevinsky (2002, 2003, 2007). A cluster algebra of rank n is an integral domain A, together with some subsets of size n called clusters whose union generates the algebra A and which satisfy various conditions.luster algebras of rank 2 [edit]. Suppose that we start with the cluster { x 1, x 2 } and take the exchange matrix with b 12 =âb 21 =1. Then mutation gives a sequence of variables x 1, x 2, x 3, x 4 ,... such that the clusters are given by adjacent pairs { x n, x n+1 }.