title: MATLAB. Counting itemsets
body: <p>Assume a m x n matrix A gives us information about purchases of m customers in a market where n items are available.
  Given a binary matrix such as A which gives us either the presence(or absence) of the jth item in the ith purchase. </p>
  
  <p>A = [ 1 0 0 1 0 1 ... 0; 
        0 1 0 1 0 0 ... 1;
        .
        . 
        . 
        1 0 0 1 0 0 ... 0 ]</p>
  
  <p>I would like to find how many customers have bought items{ {1},{1,2}, {1,2,3}... and so on. </p>
  
  <p>How would do this efficiently in MATLAB? 
  I've not been able to get a start on this. </p>