Frequencies for first 10,000 rows of ven30m variable in natlterr1998 dataset :

   Assisted |
ventilation |
       - 30 |
 minutes or |
       more |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |         20        0.20        0.20
          2 |      9,975       99.75       99.95
          9 |          5        0.05      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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