Frequencies for first 10,000 rows of proc4per variable in nhamcsopd1993 dataset :

 service #4 |
  performed |
 or ordered |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |      9,857       98.57       98.57
          1 |         91        0.91       99.48
          2 |         38        0.38       99.86
          3 |         14        0.14      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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