Frequencies for first 10,000 rows of proc2per variable in nhamcsopd1993 dataset :

 service #2 |
  performed |
 or ordered |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |      8,900       89.00       89.00
          1 |        678        6.78       95.78
          2 |        318        3.18       98.96
          3 |        104        1.04      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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