Frequencies for first 10,000 rows of proc63d variable in nhamcsopd1994 dataset :

 service #6 |
  procedure |
   code - 3 |
     digits |      Freq.     Percent        Cum.
------------+-----------------------------------
        000 |      9,997       99.97       99.97
        579 |          1        0.01       99.98
        890 |          1        0.01       99.99
        921 |          1        0.01      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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