中文说明：利用K近邻算法实现模式识别的一个小demo。对测试数据集做预处理，与训练数据集做K近邻匹配；使用5折的循环匹配；并对高维数据进行PCA降维以防止过拟合。
English Description：
Using k-nearest neighbor algorithm to realize a small demo of pattern recognition. The test data set is preprocessed, and k-nearest neighbor matching is done with the training data set; the 5-fold cycle matching is used; and the dimension of high-dimensional data is reduced by PCA to prevent over fitting.