 Usage:  lorenz(y)  
 
 Input:

  y (must be positive)   n x 1 vector of original data or 
                         n x 2 matrix of classified data: 
                         first column = class means 
                         second column = frequencies. 
                         
 Output:

  Gini                   number in [0,1], Gini coefficient 
                         
  Herfindahl             number in [0,1], Herfindahl measure of concentration 
                         
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(C) MD*TECH Method and Data Technologies, 17.8.2000
