angle between 2 vectors each time

Hello,

 I'm working with experimental data, and I want to calculate a angle between 2 lines or vectors for each group of points that changes through time.
 My code to do it is:

for j = 1:size (dados,1);

      x1 = o_x;
      x2 = q_x;
      y1 = o_y;
      y2 = q_y;
      x3 = q_x;
      x4 = j_x;
      y3 = q_y;
      y4 = j_y;

  vetor1 =[ x1(j),y1(j)]-[x2(j),y2(j)];
  vetor2 = [x3(j),y3(j)]-[x4(j),y4(j)];

      angulo(j+1,1) = acos( dot (vetor1(j),vetor2(j))./ norm(vetor1))./norm(vetor2);

end

 My data is like it:

time    o_x    o_y ...
0.01    234    364
0.02    253    456
(...)
0.03    286    654

 And the error is

??? Index exceeds matrix dimensions.

Can you help me?

Answer 1

[Walter Roberson]

vetor1(j,:) =[ x1(j),y1(j)]-[x2(j),y2(j)]; vetor2(j,:) = [x3(j),y3(j)]-[x4(j),y4(j)];

      angulo(j+1,1) = acos( dot (vetor1(j,:),vetor2(j,:))./ norm(vetor1(j,:)))./norm(vetor2(j,:));