Therefore, a criticalissue of applying linear discriminant analysis (LDA) and quadratic discriminantanalysis(QDA) is both the singularity and instability of the covarianee matrix.

• 因此，使用线性鉴别分析(LDA)与二次判别分析(QDA)算法所要面对的关键问题是如何解决协方差矩阵的奇异性和不稳定性。