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INTRODUCTION TO KNOWLEDGE DISCOVERY AND DATA MINING - CHAPTER 5

Automatic Clustering Detection - Khi con người cố gắng làm cho ý nghĩa của các câu hỏi phức tạp, xu hướng tự nhiên của chúng tôi là để phá vỡ đối tượng thành những miếng nhỏ hơn, mỗi trong số đó có thể được giải thích đơn giản hơn. Clustering là một kỹ thuật được sử dụng để kết hợp các đối tượng quan sát thành các nhóm, cụm sao cho: Mỗi nhóm hoặc cụm được đồng nhất hoặc nhỏ gọn đối với một số đặc điểm. Đó là, các đối tượng trong mỗi nhóm tương tự như. | Chapter 5 Automatic Clustering Detection When human beings try to make sense of complex questions our natural tendency is to break the subject into smaller pieces each of which can be explained more simply. Clustering is a technique used for combining observed objects into groups or clusters such that Each group or cluster is homogeneous or compact with respect to certain characteristics. That is objects in each group are similar to each other. Each group should be different from other groups with respect to the same characteristics that is objects of one group should be different from the objects of other groups. 5.1 Searching for Clusters For most data mining tasks we start out with a pre-classified training set and attempt to develop a model capable of predicting how a new record will be classified. In clustering there is no pre-classified data and no distinction between independent and dependent variables. Instead we are searching for groups of records the clusters that are similar to one another in the expectation that similar records represent similar customers or suppliers or products that will behave in similar ways. Automatic cluster detection is rarely used in isolation because finding clusters is not an end in itself. Once clusters have been detected other methods must be applied in order to figure out what the clusters mean. When clustering is successful the results can be dramatic One famous early application of cluster detection led to our current understanding of stellar evolution. Star Light Star Bright. Early in this century astronomers trying to understand the relationship between the luminosity brightness of stars and their temperatures made scatter plots like the one in Figure 5.1. The vertical scale measures luminosity in multiples of the brightness of our own sun. The horizontal scale measures surface temperature in degrees Kelvin degrees centigrade above absolute 0 the theoretical coldest possible temperature where molecular motion ceases . .