Frequencies for first 10,000 rows of ono2 variable in nhamcsed2011 dataset :

    Initial |
      vital |
  signs: On |
  oxygen on |
    arrival |      Freq.     Percent        Cum.
------------+-----------------------------------
      Blank |      1,120       11.20       11.20
    Unknown |      1,045       10.45       21.65
        Yes |        390        3.90       25.55
         No |      7,445       74.45      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 28 Mar 2016