Frequencies for first 10,000 rows of arrems variable in nhamcsed2010 dataset :

 Arrival by |
  ambulance |      Freq.     Percent        Cum.
------------+-----------------------------------
      blank |        223        2.23        2.23
    unknown |        227        2.27        4.50
        yes |      1,679       16.79       21.29
         no |      7,871       78.71      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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