Szukana fraza: [Abstract = "In this paper, we develop a \?\-analysis for nonnegative matrices and apply the results to analyse robust stability of positive linear continuous\-time systems under arbitrary affine parameter perturbations. It is shown that real and complex stability radii of positive systems coincide for arbitrary affine perturbation structures, in particular for block\-diagonal disturbances. Estimates and computable formulae are derived for these stability radii."]