nlev Leverrier's algorithm

## Syntax

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

## Arguments

A

  real square matrix

z

  character string

rmax

  optional parameter (see `bdiag`)

## Description

`[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!

## Examples

    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))

## See also

- coff
- coffg
- glever
- ss2tf