title: Read matrices as cell array from long longitudinal matlab data
body: <p>Assume the following hypothetical Matlab data (as column vectors): for 3 subjects (i=1 to 3) each provides three measurements y1, y2 , y3, over 5 time points (j=1 to 5) or less (unbalanced). The original data set is bigger. so I need to use cell array. I need at the end have Y=cell(3,1), such that, for a subject i, Y{i} is a matrix represents the repeated measures for subject i.  </p>
  
  <pre><code>i   j   y1  y2  y3
  
  1   1   1.0 0.6 0.8
  1   2   0.8 0.7 0.2
  1   3   1.0 0.7 0.9
  1   4   1.0 0.8 0.7
  1   5   0.7 0.8 0.9
  
  2   1   0.5 0.7 0.8
  2   2   0.4 0.7 0.6
  2   3   0.4 0.5 0.8
  
  3   1   0.4 0.5 0.7
  3   2   0.5 0.6 0.8
  3   3   0.5 0.6 0.8
  3   4   0.6 0.6 0.8
  </code></pre>
  
  <p>So I need them look like</p>
  
  <pre><code>Y{1}=       
  1.0 0.6 0.8
  0.8 0.7 0.2
  1.0 0.7 0.9
  1.0 0.8 0.7
  0.7 0.8 0.9
  
  Y{2}=       
  0.5 0.7 0.8
  0.4 0.7 0.6
  0.4 0.5 0.8
  
  Y{3}=       
  0.4 0.5 0.7
  0.5 0.6 0.8
  0.5 0.6 0.8
  0.6 0.6 0.8
  </code></pre>
  
  <p>I need also to use i and j to help in indexing</p>