GENERALIZED RANK ANNIHILATION METHOD .1. DERIVATION OF EIGENVALUE PROBLEMS

Rank annihilation factor analysis (RAFA) is a method for multicomponen t calibration using two data matrices simultaneously, one for the unkn own and one for the calibration sample. In its most general form, the generalized rank annihilation method (GRAM), an eigenvalue problem has to be solved. In this first paper different formulations of GRAM are compared and a slightly different eigenvalue problem will be derived. The eigenvectors of this specific eigenvalue problem constitute the tr ansformation matrix that rotates the abstract factors from principal c omponent analysis (PCA) into their physical counterparts. This reformu lation of GRAM facilitates a comparison with other PCA-based methods f or curve resolution and calibration. Furthermore, we will discuss two characteristics common to all formulations of GRAM, i.e. the distinct possibility of a complex and degenerate solution. It will be shown tha t a complex solution-contrary to degeneracy-should not arise for compo nents present in both samples for model data.