EigTool is a MATLAB GUI for computing eigenvalues, pseudospectra and related quantities for nonsymmetric matrices, both dense and sparse. The following list summarises the main features:

• Graphical interface to eigs
• Computation of eigenvalue condition numbers
• Plots of eigenmodes
• Computation of the field of values (numerical range)
• Computation of pseudospectra

This documentation assumes that you have already downloaded the latest version of EigTool, and have followed all of the installation instructions on that page.

Quick start

The simplest way to begin using EigTool is to type eigtool at the MATLAB command prompt; EigTool will start up and wait for you to give it a matrix:

Alternatively, if you already have a matrix you would like to compute the pseudospectra of (say A), type eigtool(A).

If you are unfamiliar with pseudospectra, try running the Pseudospectra Tutorial, available through the Help menu, or there are many examples that can be viewed using the Demos menu. For a more detailed look, the contains many more examples and explinations to help start you off. If you already have a matrix, click on the New Matrix button to start exploring. As a rule, EigTool computations are usually quite fast for matrices of dimensions in the low hundreds.

For a description of all of the types of matrices that EigTool can handle, see Matrix Types.

Interactive EigTool use

Once the eigenvalues and pseudospectra of your matrix have been computed, the full list of features of EigTool can be used:

These break down into three categories:

• Menus
• Buttons
• Panes

The original version of EigTool was designed and built at Oxford University during 2000-2002 by Thomas G. Wright in collaboration with Mark Embree and Lloyd N. Trefethen.

Disclaimer

EigTool home page.