Frequencies for first 10,000 rows of prov1590 variable in pos1991 dataset :

    patient |
   dialysis |
   training |
       code |      Freq.     Percent        Cum.
------------+-----------------------------------
            |      9,895       98.95       98.95
          A |        102        1.02       99.97
          M |          2        0.02       99.99
          T |          1        0.01      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 26 Jan 2016