 Usage:  s = quantile (x, a)  
 
 Input:

  x                      array 
                         
  a                      level for the quantiles (has to be in [0,1]) 
                         
 Output:

  s                      for each column in x the empirical quantiles 
                         
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(C) MD*TECH Method and Data Technologies, 17.8.2000
