自己编写的KNN算法，不用工具包就可实现。kNN算法的核心思想是如果一个样本在特征空间中的k个最相邻的样本中的大多数属于某一个类别，则该样本也属于这个类别，并具有这个类别上样本的特性.(The core idea of the kNN algorithm is that if the majority of the k most neighboring samples of a sample in the feature space belong to a particular category, the sample also belongs to this category and has the characteristics of the sample on that category)