Newton Raphson with convergence control

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Henrik 2014-11-13

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https://ww2.mathworks.cn/matlabcentral/answers/162540-newton-raphson-with-convergence-control

评论： Geoff Hayes 2014-11-13

Hi!

I am wondering is someone please can help me with the while-loop in a program that should perform newton-raphson and to write the convergence (K) in the answer?

I have put the equation given in the problem in a function file called R and it's derivative in a function called Rd.

I have been told that K should be around 0.3-0.7

The correct x is 1,21952*10^-7

The code as it looks now:

x = 1; % Start guess
tolerance =10^(-6); %Tolerance given in the problem
nmax=20; %Maximum number of iterations                    
n=0; %Start value for number of iterations
disp('     K')
disp('---------------------------')
while abs(x)> tolerance && n<nmax; 
    f = R(x); %Function 
    fprim = Rd(x); %The functions derivative
    dx = f/fprim; 
    dxOld = dx;
    K = dx/dxOld.^2;
    eps = abs(x)/abs(R(x));
    disp (K)
    x = x - dx; 
    n=n+1;
end
format long
x