Frequencies for first 10,000 rows of proc6 variable in nhamcsopd2010 dataset :

procedure 6 |
  - 4 digit |      Freq.     Percent        Cum.
------------+-----------------------------------
         -9 |      9,988       99.88       99.88
       4562 |          1        0.01       99.89
       4701 |          1        0.01       99.90
       4823 |          1        0.01       99.91
       8579 |          1        0.01       99.92
       8619 |          1        0.01       99.93
       863- |          1        0.01       99.94
       8821 |          1        0.01       99.95
       8938 |          3        0.03       99.98
       9509 |          1        0.01       99.99
       9999 |          1        0.01      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 28 Mar 2016