Frequencies for first 10,000 rows of proc2per variable in nhamcsopd1994 dataset :

 service #2 |
  performed |
 or ordered |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |      8,874       88.74       88.74
          1 |        689        6.89       95.63
          2 |        309        3.09       98.72
          3 |        128        1.28      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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