Frequencies for first 10,000 rows of venl30 variable in natl1995 dataset :

   Assisted |
ventilation |
- less than |
 30 minutes |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |         49        0.49        0.49
          2 |      9,897       98.97       99.46
          9 |         54        0.54      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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