Frequencies for first 10,000 rows of arrive variable in nhamcsed2008 dataset :

              mode of arrival |      Freq.     Percent        Cum.
------------------------------+-----------------------------------
                        blank |        197        1.97        1.97
                      unknown |        349        3.49        5.46
                    ambulance |      1,713       17.13       22.59
public service (nonambulance) |        141        1.41       24.00
      personal transportation |      7,600       76.00      100.00
------------------------------+-----------------------------------
                        Total |     10,000      100.00

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