Frequencies for first 10,000 rows of ven30m variable in natl1990 dataset :

   Assisted |
ventilation |
       - 30 |
 minutes or |
       more |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |         41        0.41        0.41
          2 |      9,891       98.91       99.32
          8 |          1        0.01       99.33
          9 |         67        0.67      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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