Structured EigTool

Numerical Linear Algebra Group

Structured EigTool

Structured singular values and pseudospectra play an important role in assessing the properties of a linear system under structured perturbations. Structured Eigtool is a free Matlab interface for plotting structured pseudospectra. In particular, it supports the computation of real, skew-symmetric, Hermitian and Hamiltonian pseudospectra. Structured EigTool is heavily based on the EigTool [1] software package for plotting unstructured pseudospectra and inherits much of its interface.

Structured pseudospectra examples

Real pseudospectrum of the Demmel matrix

Skew-symmetric pseudospectrum of the Rump matrix

Download Structured Eigtool

seigtool.tar.gz, (beta version, August 2009)
This code is research code. If you find bugs, please let us know. If you publish a research paper using this code, we will appreciate if you cite the paper [3] describing our implementation.


  1. T. G. Wright, Eigtool,, 2002.
  2. M. Karow, mu-values and spectral value sets for linear perturbation classes defined by a scalar product, submitted, 2007.
  3. M. Karow, E. Kokiopoulou and D. Kressner, On the computation of structured singular values and pseudospectra, submitted, August, 2009.


This software package is delivered "as is". The author and maintainer make no representation or warranties, express or implied, with respect to the software package. In no event shall the author or maintainer be liable for loss of profits, loss of savings, or direct, indirect, special, consequential, or incidental damages.