how world i find the lowest root with bisection

Question

adriana resendez 2015-3-3

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/181344-how-world-i-find-the-lowest-root-with-bisection

回答： rantunes 2015-3-3

function [xr ea iter] = bisect(func, x1, xu, es, maxit)
% function [xr ea iter] = bisect(func, x1, xu, es, maxit)
% bisection method
if func(x1)*func(xu)>=0, error('no sign change'); end
xold = x1;
for iter = 1:maxit
    xr = (xL+xU)
    xr2 = roots([1 0 -3 -1]);
    test = func(xL)*func(xr);
    ea = abs((xr-xold)/xr)*100;
    if test<0,xU = xr;
    elseif test>0, xL = xr;
    else ea = 0;
    end
    if ea<=es, break; end
    xold = xr;
end
end