Infinite loop in False postion method
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R Abhinandan
on 27 Oct 2020
Commented: Cris LaPierre
on 27 Oct 2020
Here is my code for false position method and im getting a infinite loop, i want it to stop at tol=10^-4, can someone help?
a=0.5;
b=1;
tol=0.0001;
counter=0;
f =@(x) exp(x)-3*x^2;
while abs(b-a)>tol
c= b - (f(b)* (b-a)/(f(b)-f(a)));
if f(a)*f(c)<0
b=c;
end
if f(a)*f(c)>0
a=c;
end
counter=counter+1;
er=abs(a-b);
errorcounter(counter)=er;
end
figure
hold on
plot(errorcounter)
title('Convergence of False Position')
ylabel('Error')
xlabel('Iterations')
axis ([0 5 0 9e-04])
1 Comment
Cris LaPierre
on 27 Oct 2020
btw, hold on is unnecessary here. When used, it should always be paired with hold off.
Accepted Answer
Cris LaPierre
on 27 Oct 2020
I don't understand what your approach is, but by converting your while loop to a for loop, I can see that your error stops decreasing at 0.09. Here's a simplified version of your code.
a=0.5;
b=1;
f =@(x) exp(x)-3*x^2;
% while abs(b-a)>tol
for loop = 1:10
c= b - (f(b)* (b-a)/(f(b)-f(a)));
if f(a)*f(c)<0
b=c;
elseif f(a)*f(c)>0
a=c;
end
er=abs(a-b)
end
2 Comments
Cris LaPierre
on 27 Oct 2020
Edited: Cris LaPierre
on 27 Oct 2020
I understand. Check your algorithm. You have not implemented it correctly.
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