Index exceeds the number of array elements (1) error

Greetings,

I'm trying to make a position analysis of a mechanism via Newton-Raphson algorithm and when I constructed my model matrixes, I have this error "Index exceeds the number of array elements (1)" and I couldn't decide how to reduce my index. Could that error occurs because of that I'm missing something while giving the parameters? Whole model is given below:

clc, clear all;

%initiating physical parameters
a2=29;a3=15;a4=16;a5=27;a6=25;th4=332*pi/180;thd=240*pi/180;

%initiating max iteration
Nmax=100;

%initiating guess values for th3, th5, th6, to
x=[14*pi/180,59*pi/180,323*pi/180,32];

%initiate error tolerance
xe=0.001*abs(x);

%initiating system inputs
dth=5*pi/180;
th2=-30*pi/180:dth:30*pi/180;
w2=35*ones(1,length(th2));
al2=0*ones(1,length(th2));
%-------------------------
xe=transpose(abs(xe));
kerr=1;
for k=1:1:length(th2);
    for n=1:Nmax
        %-------------------
       %assign initial gues to unknowns
       th3(k)=x(1);th5=x(2);
       th6=x(3);to=x(4);

         %jacobian matrix
         J=zeros(4,4)
         J(1,1)=-a3*sin(th3(k));J(2,1)=a3*cos(th3(k));
         J(3,2)=-a5*sin(th5(k));
         J(3,3)=-a6*sin(th6(k));
         J(3,4)=-1;
         J(4,2)=a5*cos(th5(k));J(4,3)=a6*cos(th6(k));

         %INPUT: FUNCTIONS
         f=zeros(4,1);
         f(1,1)=(a2*cos(th2(k))+a3*cos(th3(k))+a4*cos(th4)+a5*cos(thd)-43);
         f(2,1)=(a2*sin(th2(k))+a3*sin(th3(k))+a4*sin(th4)+a5*sin(thd)+31);
         f(3,1)=(a5*cos(th5(k))+a6*cos(th6(k))-to(k));
         f(4,1)=(a5*sin(th5(k))+a6*sin(th6(k))-12);

         %----------------
         eps=inv(J)*f;x=x+transpose(eps);

         if abs(eps)<xe
             kerr=0;break
         end
      end

      if kerr==1
          'Error nr'
      end
      th3(k)=x(1);th5(k)=x(2);
      th6(k)=x(3);to(k)=x(4)
  end

thank you for answers.

Answer 1

[Bruno Luong]

         %assign initial gues to unknowns
         th3(k)=x(1);th5=x(2);
         th6=x(3);to=x(4);

I think it should be

       th3(k)=x(1);
       th5(k)=x(2);
       th6(k)=x(3);
       to(k)=x(4);

[Zafer Duyenli]

Thanks a lot!