TWO_MEANS_1D - returns the clustering that optimizes the 
  objective function of the k-means algorithm for the input 
  vector.
    [CUTOFF, CLUSTERS, DISTANCE, OF, MEAN1, MEAN2]=
    TWO_MEANS_1D(A) returns the cutoff value of the clustering, 
    the cluster structure, the separation distance, the value 
    of the objective function and the two mean values.  
 
  Copyright 2011 Dimitrios Zeimpekis, Eugenia Maria Kontopoulou, 
                 Efstratios Gallopoulos