Frequencies for first 10,000 rows of ven30m variable in natl1994 dataset :

   Assisted |
ventilation |
       - 30 |
 minutes or |
       more |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |        117        1.17        1.17
          2 |      9,827       98.27       99.44
          9 |         56        0.56      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 22 Dec 2015