@ARTICLE\{IMM2019-07151, author = "A. A. Nielsen", title = "Fast matrix based computation of eigenvalues and the Loewner order in PolSAR data", year = "2019", month = "nov", journal = "{IEEE} Geoscience and Remote Sensing Letters (Early Access)", volume = "", editor = "", number = "", publisher = "", note = "Matlab code in zip file", url = "http://doi.org/10.1109/LGRS.2019.2952202", abstract = "We describe calculation of eigenvalues of 2x2 or 3x3 Hermitian matrices as used in the analysis of multilook polarimetric {SAR} data. The eigenvalues are calculated as the roots of quadratic or cubic equations. We also describe pivot based calculation of the Loewner order for partial ordering of differences between such matrices. The methods are well suited for fast matrix oriented computer implementation and the speedup over simpler calculations based on built-in eigenproblem solvers is enormous." }