Frequencies for first 10,000 rows of prov1235 variable in pos1991 dataset :

 stations - |
 peritoneal |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |      9,917       99.17       99.17
          1 |         54        0.54       99.71
          2 |         17        0.17       99.88
          3 |          1        0.01       99.89
          4 |          5        0.05       99.94
          7 |          1        0.01       99.95
          8 |          3        0.03       99.98
          9 |          1        0.01       99.99
         11 |          1        0.01      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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