newton.m

various matlab programs to slove various problems

function [xvect,xdif,fx,nit]=newton(x0,nmax,toll,fun,dfun)
err=toll+1; nit=0; xvect=x0; x=x0; fx=eval(fun); xdif=[];
while (nit < nmax & err > toll),
    nit=nit+1; x=xvect(nit); dfx=eval(dfun);
    if (dfx == 0), err=toll*1.e-10;
       disp(' Stop for vanishing dfun  ');
    else,
       xn=x-fx(nit)/dfx; err=abs(xn-x); xdif=[xdif; err];
       x=xn; xvect=[xvect;x]; fx=[fx;eval(fun)];
    end;
end;