I need to change this code into one that can solve complex roots
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Elena Cecilia Valero Garza
2022 年 9 月 12 日
I have this Newton-Raphson method code, but I need to change it into a code that can actually solve polynomials and give as an answer complex roots.
Code:
function [tabla, raiz]=newtonraphsonMN(f,xa,errorD,imax)
tabla=[];
error=Inf;
i=0;
xr=NaN;
df=diff(f);
while error>errorD && i<=imax
i=i+1;
fxa=double(subs(f,xa));
fpxa=double(subs(df,xa));
xr=xa-fxa/fpxa;
error=100*abs((xr-xa)/xr);
tabla=[tabla; [xa fxa fpxa xr error]];
xa=xr;
end
%raiz
raiz=xr;
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採用された回答
John D'Errico
2022 年 9 月 12 日
編集済み: John D'Errico
2022 年 9 月 13 日
Interesting. It does not work? :) Gosh, You could have fooled me. I'll try an example. (I've attached the code you gave, so it will be used.)
syms X
f = X^2 + X + 1;
Does f has complex roots?
solve(f)
vpa(ans)
Of course. I'd not have used an example that lacks complex roots, since that is your question.
[tabla, raiz]=newtonraphsonMN(f,1 + i,1e-12,100);
Strange.
tabla
format long
raiz
To me, it seems to have worked. But then, what do I know? :)
(Hint: Do you see what I did different?)
2 件のコメント
Torsten
2022 年 9 月 13 日
To solve for polynomial roots, use MATLAB's "roots" command.
Newton's method will only give you one solution per call. Which one you get depends on the initial guess.
Example:
To determine all roots of p(x) = x^2+x+1:
p = [1 1 1];
sol = roots(p)
polyval(p,sol)
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