Frequencies for first 10,000 rows of uab_ven30m variable in natl2004 dataset :

   Assisted |
Ventilation |
>= 30 min U |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |         55        0.55        0.55
          2 |      8,760       87.60       88.15
          9 |      1,185       11.85      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 21 Jan 2016