 Usage:  v = mat2vec(d)  
 
 Input:

  d                      n x n matrix (for example a correlation matrix or 
                         a distance matrix) 
                         
 Output:

  v                      n(n-1)/2 x 1 matrix containing the values of the upper 
                         triangle of d (for instance, the vector v 
                         can be used as the input parameter of the 
                         function "agglom" if d contains distances) 
                         
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(C) MD*TECH Method and Data Technologies, 17.8.2000
