nlev

nlev — Leverrier's algorithm

Calling sequence

[num,den]=nlev(A,z [,rmax])

`A`	: real square matrix
`z`	: character string
`rmax`	: optional parameter (see `bdiag`)

[num,den]=nlev(A,z [,rmax]) computes (z*eye()-A)^(-1)

by block diagonalization of A followed by Leverrier's algorithm on each block.

This algorithm is better than the usual leverrier algorithm but still not perfect!



A=rand(3,3);x=poly(0,'x');
[NUM,den]=nlev(A,'x')
clean(den-poly(A,'x'))
clean(NUM/den-inv(x*eye()-A))

F. Delebecque., S. Steer INRIA;