Frequencies for first 10,000 rows of proc3per variable in nhamcsopd1993 dataset :

 service #3 |
  performed |
 or ordered |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |      9,617       96.17       96.17
          1 |        257        2.57       98.74
          2 |         94        0.94       99.68
          3 |         32        0.32      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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