I. Introduction
Cluster analysis is an important research topic in the field of data minin g, It not only can be used as a separate tool to find data in the database which are some differences in the distribution of information but also can be used as a preprocessing step of the algorithm of other data mining. Clustering as an important method in data mining is a discovery process that groups a set of data such that the intra-cluster similarity is maximized and the inter-cluster similarity is minimized.