y = poly (A) ¶y = 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.
(c) ¶(c, x) ¶str = polyout (…) ¶Display a formatted version of the polynomial c.
The formatted polynomial
c(x) = c(1) * x^n + … + c(n) x + c(n+1)
is returned as a string or written to the screen if nargout is zero.
The second argument x specifies the variable name to use for each term
and defaults to the string "s".
See also: polyreduce.