title: Comments on "on image matrix based feature extraction algorithms".
abstract: A class of image-matrix-based feature extraction algorithms has been discussed earlier. The correspondence argues that 2-D principal component analysis and Fisher linear discriminant (FLD) are equivalent to block-based PCA and FLD. In this correspondence, we point out that this statement is not rigorous.
authors.forename: Quanxue
authors.initials: Q
authors.lastname: Gao
authors.forename: Lei
authors.initials: L
authors.lastname: Zhang
authors.forename: David
authors.initials: D
authors.lastname: Zhang
authors.forename: Jian
authors.initials: J
authors.lastname: Yang
mesh_terms: D000465:Algorithms; D001185:Artificial Intelligence; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D010363:Pattern Recognition, Automated / Q000379:methods*; D025341:Principal Component Analysis; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity