Frequencies for first 10,000 rows of ono2 variable in nhamcsed2012 dataset :

    Initial |
      vital |
  signs: On |
  oxygen on |
    arrival |      Freq.     Percent        Cum.
------------+-----------------------------------
      Blank |        354        3.54        3.54
    Unknown |      1,253       12.53       16.07
        Yes |        310        3.10       19.17
         No |      8,083       80.83      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 7 Nov 2016