I want to get the values from the last two iteration

1 次查看（过去 30 天）
Jan Kyle Dismas
Jan Kyle Dismas 2022-3-24
编辑： Jan Kyle Dismas 2022-3-24
Hi, i am creating a program, that follows the secant method, wherein you input two guesses which are xi1, xi and a error tolerance, the problem i have here is that i do not know how to replace the newxi as xi and the last xi from the iteration as xi1. In the image we can see that as iteration 3 and beyond is has the same values all the way since i do not know how to replace xi and xi1. by the way, xi at i=0 is the first guess while xi at i=1 is the xi1 or the second guess
disp('i xi f(xi) ear') %Header
for i=0:200
if i==0
xinew=xi1; %Calculate xi
fxi=y(xinew);
elseif i==1
xinew=xi;
fxi=y(xinew);
elseif i>1
xinew=xi-((y(xi)*(xi-xi1))/(y(xi)-y(xi1))); %Calculate xi
fxi=y(xinew);
end
fprintf('%2.i %18.8f %15.8f \n',i,xinew,fxi) %Creation of rows in the iteration

请先登录，再回答此问题。

回答（1 个）

Torsten
Torsten 2022-3-24
% Tolerances, Maximum number of iterations
tolF = 1e-6;
tolX = 1e-8;
itermax = 30;
% Start values
xim2 = 6;
xim1 = 4;
fim2 = f(xim2);
fim1 = f(xim1);
% Initialization
errorF = 1.0;
errorX = 1.0;
iter = 0;
% Iteration loop
while (errorF > tolF || errorX > tolX) && iter < itermax
xi = xim1 - fim1*(xim1-xim2)/(fim1-fim2)
fi = f(xi);
errorF = abs(fi);
errorX = abs(xi-xim1)
fim2 = fim1;
fim1 = fi;
xim2 = xim1;
xim1 = xi;
iter = iter + 1;
end
% Result
xi, fi
% Function definition
function y = f(x)
y = (x-3).^2 - 4
end

类别

在 Help Center 和 File Exchange 中查找有关 Financial Data 的更多信息

标签

产品


版本

R2022a

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by