说明：  主成分分析：通过正交变换将一组可能存在相关性的变量转换为一组线性不相关的变量，转换后的这组变量叫主成分。
(Principal Component Analysis (PCA): A set of variables that may be correlated are transformed into a set of linear irrelevant variables by orthogonal transformation. The transformed variables are called principal components.)