Resolve a Complex equation in a loop WHILE

Question

Eduardo 2014-4-13

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回答： Alberto 2014-4-14

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Hello,

I am trying to resolve a Newton-Raphson method by a complex equation.

But I am with the following error:

 Attempted to access f(2.07279); index must be a positive integer or logical.
 Error in teste04 (line 17)   x = (x - (f(x)/df(x)));

I wrote the code:

 x=2; %initial value
 x_old= 12;
 % c = 1.1 % If c is greater than the unity all the roots will be complex
 c = 0.99; % If c is lower than the unity all the roots will be real
 f(x)=(1-((c*x/2)*(log(x+1)-log(x-1)))); % the function that I would like to calculate the root  by the newton-raphson method
 df(x)=((c/2)*((log(x+1)-log(x-1))+(2*x/(x^2-1)))); % derivative of the f(x)
 tolerance=0.00001; % the method will stop if the difference between the the diff = [x(i+1) - x(i)] were lower than 1E-5
 while abs(x_old-x) > tolerance
    x_old = x;
    x = (x - (f(x)/df(x)));
    pause;
 end