 Usage:  {xr,r} = tableN(x)  
 
 Input:

  x                      n x N matrix, the columns correspond to the 
                         variables. 
                         
 Output:

  xr                     m x N matrix, includes all possible 
                         combinations of values, sorted by last column. 
                         
  r                      m x 1 vector, contains the number of replications 
                         of each combination. Some values may be 0. 
                         The sum of r is equal the count of observations. 
                         
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(C) MD*TECH Method and Data Technologies, 17.8.2000
