Function Reference
— Function File: poly (a)

If a is a square N-by-N matrix, poly (a) is the row vector of the coefficients of det (z * eye (N) - a), the characteristic polynomial of a. As an example we can use this to find the eigenvalues of a as the roots of poly (a).

          roots(poly(eye(3)))
           1.00000 + 0.00000i
           1.00000 - 0.00000i
           1.00000 + 0.00000i

In real-life examples you should, however, use the eig function for computing eigenvalues.

If x is a vector, poly (x) is a vector of coefficients of the polynomial whose roots are the elements of x. That is, of c is a polynomial, then the elements of d = roots (poly (c)) are contained in c. The vectors c and d are, however, not equal due to sorting and numerical errors.

See also: eig roots