GeezerVison is showing octave.sourceforge.io — Function Reference: poly
- : poly (A)
- : poly (x)
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.
For example, the following code finds the eigenvalues of A which are
the roots of poly (A).
roots (poly (eye (3)))
⇒ 1.00001 + 0.00001i
1.00001 - 0.00001i
0.99999 + 0.00000i
In fact, all three eigenvalues are exactly 1 which emphasizes that for
numerical performance the eig function should be used to compute
eigenvalues.
If x is a vector, poly (x) is a vector of the
coefficients of the polynomial whose roots are the elements of x.
That is, if c is a polynomial, then the elements of
d = roots (poly (c)) are contained in c. The
vectors c and d are not identical, however, due to sorting and
numerical errors.
See also: roots, eig.
Package: octave