Incremental two-dimensional linear discriminant analysis with applications to face recognition

Two dimensional linear discriminant analysis (2DLDA) has been verified as an effective method to solve the small sample size (SSS) problem in linear discriminant analysis (LDA). However, most of the existing 2DLDA techniques do not support incremental subspace analysis for updating the discriminant eigenspace. Incremental learning has proven to enable efficient training if large amounts of training data have to be processed or if not all data are available in advance as, for example, in on-line situations. Instead of having to re-training across the entire training data whenever a new sample is added, this paper proposed an incremental two-dimensional linear discriminant analysis (I2DLDA) algorithm with closed-form solution to extract facial features of the appearance image on-line. The proposed I2DLDA inherits the advantages of the 2DLDA and the Incremental LDA (ILDA) and overcomes the number of the classes or chunk size limitation in the ILDA because the size of the between-class scatter matrix and the size of the within-class scatter matrix in the I2DLDA are much smaller than the ones in the ILDA. The results on experiments using the ORL and XM2VTS databases show that the I2DLDA is computationally more efficient than the batch 2DLDA and can achieve better recognition results than the ILDA.