How can i put a stopping criterion for this bisection method code in matlab?

2 次查看（过去 30 天）
Ja
Ja 2022-10-8
编辑： Torsten 2022-10-8
I want to put a stopping criterion of 2% in my code where, once I run the code, the result will stop if the relative error r_e is equal to 2%.
I need help on where should I put commands and how to do it
here's my code
f_x= @(x)sin(5*x)+cos(2*x)
p_old = 0; % give an initial value to it
x_l =2; x_u = 10;
n = 20;
for i=1:n
f_l = f_x(x_l);
f_u = f_x(x_u);
p = (x_l+x_u)/2;
f_m = f_x(p);
if (f_l*f_m)<0
x_u=p;
elseif (f_u*f_m)<0
x_l=p;
end
r_e = abs((p-p_old)/(p));
p_old = p; % assign the p_old after relative error
table(i, :)={i-1 p r_e};
fprintf('%d %d %d \n', table{i, :});
end

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回答（2 个）

Ghazwan
Ghazwan 2022-10-8
The code for the bisection method is available here
https://www.mathworks.com/matlabcentral/fileexchange/72478-bisection-method
Torsten
Torsten 2022-10-8
编辑：Torsten 2022-10-8
Ran in:
f_x= @(x)sin(5*x)+cos(2*x);
p_old = 0; % give an initial value to it
x_l =2; x_u = 10;
x=x_l:0.01:x_u;
hold on
plot(x,f_x(x))
n = 20;
eps = 1e-6;
for i=1:n
f_l = f_x(x_l);
f_u = f_x(x_u);
p = (x_l+x_u)/2;
f_m = f_x(p);
if (f_l*f_m)<0
x_u=p;
elseif (f_u*f_m)<0
x_l=p;
end
plot(p,f_x(p),'o')
r_e = abs((p-p_old)/(p));
if r_e < eps
break
end
p_old = p; % assign the p_old after relative error
table(i, :)={i-1 p r_e};
fprintf('%d %d %d \n', table{i, :});
end
0 6 1 1 8 2.500000e-01 2 9 1.111111e-01 3 8.500000e+00 5.882353e-02 4 8.750000e+00 2.857143e-02 5 8.875000e+00 1.408451e-02 6 8.812500e+00 7.092199e-03 7 8.781250e+00 3.558719e-03 8 8.765625e+00 1.782531e-03 9 8.757812e+00 8.920607e-04 10 8.753906e+00 4.462294e-04 11 8.751953e+00 2.231645e-04 12 8.750977e+00 1.115947e-04 13 8.751465e+00 5.579423e-05 14 8.751709e+00 2.789634e-05 15 8.751587e+00 1.394836e-05 16 8.751526e+00 6.974230e-06 17 8.751556e+00 3.487103e-06 18 8.751572e+00 1.743548e-06
hold off

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