Frequencies for first 10,000 rows of uab_venl30 variable in natl2004 dataset :

   Assisted |
Ventilation |
 < 30 min U |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |        501        5.01        5.01
          2 |      8,314       83.14       88.15
          9 |      1,185       11.85      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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