MATLAB Function Reference

compan

Companion matrix

Syntax

A = compan(u)

Description

A = compan(u) returns the corresponding companion matrix whose first row is -u(2:n)/u(1), where u is a vector of polynomial coefficients. The eigenvalues of compan(u) are the roots of the polynomial.

Examples

The polynomial

has a companion matrix given by

u = [1  0  -7  6]
A = compan(u)
A =
    0    7   -6
    1    0    0
    0    1    0

The eigenvalues are the polynomial roots:

eig(compan(u))
ans = 
    -3.0000
     2.0000
     1.0000

This is also roots(u).

See Also

eig, poly, polyval, roots

comet3

compass