Plot in Bisection Method

Question

Utku Palakci 2019-1-2

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/437935-plot-in-bisection-method

回答： Geoff Hayes 2019-1-2

%% Bisection Method
% f(x) = 2sin(x) + 2cos(x)
a = -1;
b = 1;
tol = 10^-3;
iter = 0;
fprintf('iter \t    a     \t       b      \t      fark\n' );
fprintf('---------------------------------------------\n' );
while (abs(a-b)>tol)
    fa = 2*sin(a) + 2*cos(a);
    fb = 2*sin(b) + 2*cos(b);
    m = (a+b)/2;
    fm = 2*sin(m) + 2*cos(m);
    if (fa*fm<0)
        b=m;
    else
        a=m;
    end
    iter = iter + 1 ;
    fprintf('%d \t %f \f \t %f \t %f \t %f\n',iter,a,b, abs(a-b),tol);
end

Hey everyone

How can I plot this code with functions showing the location of the

initial guess and the approximated root value?

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Answer 1

Geoff Hayes 2019-1-2

0
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在 MATLAB Online 中打开

Utku - I suppose that you would want to plot the m that is generated on each iteration of the loop. If that is the case, you could save that data to an array and plot that array when you exit the loop like

iter = 1;
mData = []; % create an array
while (abs(a-b)>tol)
    fa = 2*sin(a) + 2*cos(a);
    fb = 2*sin(b) + 2*cos(b);
    m = (a+b)/2;
    fm = 2*sin(m) + 2*cos(m);
    if (fa*fm<0)
        b=m;
    else
        a=m;
    end
    mData[iter] = m; % save data to array
    iter = iter + 1 ;
    fprintf('%d \t %f \f \t %f \t %f \t %f\n',iter,a,b, abs(a-b),tol);
end
plot(mData); % plot data