While defined in terms of variances and covariances, PCA is usually applied to standardized data since the results are sensitive to the often arbitrary choices of units of measurement used in a study.

• 就定义差异变量和协方差而言，PCA分析前通常要先标准化处理数据，因为，PCA对任意选择研究中的计量单元是敏感的。以下批处理文件；