If A is a square N-by-N matrix,
poly (A)is the row vector of the coefficients ofdet (z * eye (N) - A), the characteristic polynomial of A. For example, the following code finds the eigenvalues of A which are the roots ofpoly (A).roots(poly(eye(3))) ⇒ 1.00001 + 0.00001i ⇒ 1.00001 - 0.00001i ⇒ 0.99999 + 0.00000iIn fact, all three eigenvalues are exactly 1 which emphasizes that for numerical performance the
eigfunction 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.
Write formatted polynomial
c(x) = c(1) * x^n + ... + c(n) x + c(n+1)and return it as a string or write it to the screen (if nargout is zero). x defaults to the string
"s".See also: polyreduce.
Reduce a polynomial coefficient vector to a minimum number of terms by stripping off any leading zeros.
See also: polyout.