Frequencies for first 10,000 rows of proc1per variable in nhamcsopd1993 dataset :

 service #1 |
  performed |
 or ordered |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |      6,066       60.66       60.66
          1 |      2,567       25.67       86.33
          2 |        980        9.80       96.13
          3 |        387        3.87      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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