plot all roots of a polynomial which has a interval coefficient

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senhan yao
senhan yao 2021-3-24
评论： senhan yao 2021-3-24
For example, if the polynomial is: p= s^3 + a*s^2 + s + 1 which a=[2,3].
How can plot all the roots of this polynpomial? I can only figure out the roots when 'a' is fixed.
  2 个评论
Rik
Rik 2021-3-24
Wouldn't that just mean you would have to find the roots in a loop? There is an analytical way to determine the roots, but that will be a pain to implement.
senhan yao
senhan yao 2021-3-24
Yeah,it seems very laborious. I can plot the roots when 'a' is fixed. I think maybe there is a method like below to solve this problem.
P=[1 2 1 1];
z=roots(p);
scatter(real(z),imag(z));

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采纳的回答

Rik
Rik 2021-3-24
Ran in:
I meant something like this.
N=200;
Z=NaN(N,3);
a=linspace(2,3,N);
for n=1:numel(a)
p=[1 a(n) 1 1];
z=roots(p);
Z(n,1:numel(z))=z;
end
h=plot(real(Z),imag(Z));
legend({'1','2','3'},'Location','NorthWest')
[h.Color]=deal('b','r','k');

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