 Usage:  g = tree (t, cut {, opt})  
 
 Input:

  t                      n x 2 matrix produced from agglom 
                         
  cut                    scalar the cut-off value for the tree 
                         
  opt                    text matrix of optional parameters 
                         
 Output:

  g.points               m x 2 matrix for drawing trees via show 
                         
  g.index                m x 1 matrix of indices 
                         
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(C) MD*TECH Method and Data Technologies, 17.8.2000
