roots求得多项式的所有复根
function r = roots(c)%roots(p)可求得多项式p的所有复根.
%例 x^3+2x^2-3=0
% 求解
% roots()
%
%ROOTSFind polynomial roots.
% ROOTS(C) computes the roots of the polynomial whose coefficients
% are the elements of the vector C. If C has N+1 components,
% the polynomial is C(1)*X^N + ... + C(N)*X + C(N+1).
%
% See also POLY, RESIDUE, FZERO.
% J.N. Little 3-17-86
% Copyright (c) 1984-98 by The MathWorks, Inc.
% $Revision: 5.6 $$Date: 1997/11/21 23:41:05 $
% ROOTS finds the eigenvalues of the associated companion matrix.
if size(c,1)>1 & size(c,2)>1
error('Must be a vector.')
end
c = c(:).';
n = size(c,2);
r = zeros(0,1);
inz = find(c);
if isempty(inz),
% All elements are zero
return
end
% Strip leading zeros and throw away.
% Strip trailing zeros, but remember them as roots at zero.
nnz = length(inz);
c = c(inz(1):inz(nnz));
r = zeros(n-inz(nnz),1);
% Polynomial roots via a companion matrix
n = length(c);
if n > 1
a = diag(ones(1,n-2),-1);
a(1,:) = -c(2:n) ./ c(1);
r = ;
end
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