function [xi,S,L] = cubicSpline(t,y)
  n = length(t);
  z = zeros(n,1); h = zeros(n-1,1); b = zeros(n-1, 1);
  u = zeros(n,1); v = zeros(n,1);

  h = t(2:n)-t(1:n-1); b = (y(2:n)-y(1:n-1))./h;
  u(2) = 2*(h(1)+h(2)); v(2) = 6*(b(2)-b(1));

  for i=3:n-1
    u(i) = 2*(h(i)+h(i-1))-h(i-1)^2/u(i-1);
    v(i) = 6*(b(i)-b(i-1))-h(i-1)*v(i-1)/u(i-1);
  endfor

  for i=n-1:-1:2
    z(i) = (v(i)-h(i)*z(i+1))/u(i);
  endfor

  S = [];
  xi = [];
  %Gambar garis di masing-masing titik
  prevp = 0;
  L = 0;
  for i=1:n-1
    for x=t(i):0.00005:t(i+1)+0.00005
      h = t(i+1)-t(i);
      p = z(i+1)/(6*h)*(x-t(i))^3 ...
          -z(i)/(6*h)*(x-t(i+1))^3 ...
          +(y(i+1)/h-z(i+1)*h/6)*(x-t(i)) ...
          -(y(i)/h-z(i)*h/6)*(x-t(i+1));
      L = L + sqrt((p - prevp)^2 + (0.00005)^2);
      prev = p;
      S = [S,p];
      xi = [xi,x];
    endfor
  endfor
endfunction