Frequencies for first 10,000 rows of arrive variable in nhamcsed2006 dataset :

       mode of |
       arrival |      Freq.     Percent        Cum.
---------------+-----------------------------------
         blank |        230        2.30        2.30
     ambulance |      1,553       15.53       17.83
public service |        143        1.43       19.26
       walk-in |      7,841       78.41       97.67
       unknown |        233        2.33      100.00
---------------+-----------------------------------
         Total |     10,000      100.00

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