Frequencies for first 10,000 rows of ven30m variable in natl1992 dataset :

   Assisted |
ventilation |
       - 30 |
 minutes or |
       more |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |        103        1.03        1.03
          2 |      9,861       98.61       99.64
          9 |         36        0.36      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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