companion - companion matrix

Calling Sequence

A=companion(p)

Parameters

• p : polynomial or vector of polynomials
• A : square matrix

Description

Returns a matrix A with characteristic polynomial equal to p if p is monic. If p is not monic the characteristic polynomial of A is equal to p/c where c is the coefficient of largest degree in p.

If p is a vector of monic polynomials, A is block diagonal, and the characteristic polynomial of the ith block is p(i).

Examples

s=poly(0,'s');
p=poly([1,2,3,4,1],'s','c')
det(s*eye()-companion(p))
roots(p)
spec(companion(p))
 

See Also

spec  poly  randpencil  

Author

F.D.