Frequencies for first 10,000 rows of uab_ven30m variable in natlterr2003 dataset :

   Assisted |
Ventilation |
>= 30 min U |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |         30        0.30        0.30
          2 |      9,946       99.46       99.76
          8 |         23        0.23       99.99
          9 |          1        0.01      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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