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

 Arrival by |
  ambulance |      Freq.     Percent        Cum.
------------+-----------------------------------
      Blank |        134        1.34        1.34
    Unknown |        253        2.53        3.87
        Yes |      1,750       17.50       21.37
         No |      7,863       78.63      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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