说明：  Introduction to Data Mining Pang-Ning Tan chapte 4 分类基本概念课件改编版。加入 纯净度测量matlab函数，增益matlab函数，以及只有结果的例题的解题过程。
(Introduction to Data Mining Pang-Ning Tan chapte the 4 classification basic concept courseware adaptation. Join purity measurement matlab function, gain matlab function, and only the results of examples of the problem solving process.)