function [i, x]=nuton(x0, f, J)
   N=100, eps=0.00001, maxval=10000.0, i=0
   while (N>0)
   JJ=J(x0),
   if(abs(det(JJ))<eps) then error('try new x0'),
   abort,
   end;
   xn=x0-inv(JJ)*f(x0),
   if(abs(f(xn))<eps) then x=xn,
   return,
   end;
   if(abs(f(x0))>maxval) then disp(100-N),
   error('sol div'), abort,
   end;
   N=N-1, x0=xn, i=i+1,
   end;
   error('no conv'), abort;
 endfunction

Матрица Якоби:

function [J]=jacob(x)
  J=numderivative(ValEq,x)
endfunction