Newton-Rahpson Method

Arnaldo Otero

2019 4 2

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Design a function that calculates the roots of a polynomial using the NewtonRaphson method with input parameters: f(the function),df(derivative of [f]),x0(initial point),maxIter(maximum number of iterations) & rTol(Error) and output:(flag,x,numIter), where flag=1 if the error in the iteration [while loop] is as follows and 0 otherwise:

I'm not getting a correct approximation, and the flag is set to 1 which is also incorrect

function [flag,x,numIter] = Newton1D(f,df,x0,maxIter,rTol)
k=0;            %Variable para salir del while loop
iter=1;         %Variable para almacenar el numero de iteraciones en los arreglos
x=x0            %Pasos para evaluar una funcion en un valor para una funcion simbolica
numIter=1;
f=subs(f,x0);   %Evaluar la funcion f simbolica original en el valor x0
df=subs(df,x0); %Evaluar la derivada de la funcion f en el punto x0            
iter= iter+1;
   for j=1:maxIter   
          a(1,1)=x;
          j=j+1;
          w=j-1;
          a(j,1)= a(w,1)- (f)/(df);
       while(k<=maxIter && w<=maxIter)
            if (abs(a(j,1)-a(w,1)))<(abs(a(w,1))*rTol)
                flag=1;
                x=a(j,1);
                numIter= iter-1;
                k= maxIter+1;
                j=maxIter;
            else
                x=a(j,1);
                f=subs(f,x);
                df=subs(df,x);
                iter= iter+1;
                numIter= iter-1;
                k= k+1;
                j=j-1;
                flag=0;
            end
       end
    end
flag
x
numIter
end