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